Merocyanine crystallization method

Abstract

To provide 3-amino-2-cyclohexane-1-ylidene derivatives represented by the formula (1), having improved color properties, and to also provide an improved method for the purification and isolation of merocyanine compounds that minimize discolorations in the final application system.SOLUTION: The present invention relates to a method for preparing a crystalline merocyanine compound, comprising a step of dissolving a merocyanine compound in an organic polar solvent, wherein the method is performed at a pH less than 7 in the presence of an acid, wherein colored impurities at residual levels are eliminated.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention provides an improved method for crystallizing merocyanine compounds of high purity and having improved color properties. The method for preparing crystalline merocyanine comprises dissolving a merocyanine compound in an organic polar solvent, the method being carried out at a pH of less than 7.

[0002] The 3-amino-2-cyclohexan-1-ylidene derivatives of formula (1) below belong to the chemical class of merocyanines and are useful as UV absorbers for protecting household products from photodegradation and oxidative degradation, as plastic additives, preferably for food and pharmaceutical packaging applications, for preventing food photodegradation by incorporating these compounds into transparent food containers, for protecting UV-A sensitive drugs from photodegradation by incorporating UV absorbers into transparent blister foils or transparent pharmaceutical containers, as additives for photographic and printing applications, as additives for electronic applications, and for protecting ingredients in agricultural applications. [Background technology]

[0003] The merocyanine derivatives of the present invention are produced through a multi-step sequence that is affected by the formation of colored by-products. Colored impurities have the disadvantage of causing undesired discoloration in the final commercial application. The undesired discoloration is typically observed as yellowing in the final commercial product (e.g., sunscreen formulation or packaging). The ability of a merocyanine product containing such impurities to discolor the final product correlates with its original color before being mixed into the final product. The color of a merocyanine product can be measured by colorimetric methods. Among these, measuring the Gardner Index is a common method for measuring the yellowness of a substance. The more colored impurities a merocyanine product sample contains, the higher the Gardner Index value, which causes stronger discoloration in the final commercial product. Therefore, it is desirable to reduce the residual level of colored impurities. Summary of the Invention

[0004] The object of the present invention is to provide 3-amino-2-cyclohexan-1-ylidene derivatives of the following formula (1), which no longer exhibit the above-mentioned disadvantages and, in particular, have improved color properties. The present invention therefore also aims to provide improved methods for the purification and isolation of merocyanine compounds, which minimize discoloration in the final application system.

[0005] This object is achieved according to the present invention by crystallization of merocyanine compounds in specific solvents or solvent mixtures.

[0006] Surprisingly, these objectives are (a) dissolving a merocyanine compound in an organic polar solvent; (b) crystallizing the merocyanine compound from the solution obtained in step (a); and (c) isolating the merocyanine compound from the crystallization mixture of step (b). 1. A method for preparing a crystalline merocyanine compound, comprising: The following options (i) adding an acid A1 in step (a), (ii) adding an acid A2 in step (b), or (iii) adding acid A1 in step (a) and acid A2 in step (b) It has been found that this can be achieved by a method carried out at a pH below 7.

[0007] Surprisingly, the inventors have discovered that by the method for preparing a crystalline merocyanine compound as defined above, the merocyanine crystals so obtained have a Gardner index of less than 5, measured according to DIN EN ISO 4630 with a spectrophotometer PE Lambda 650. Even more surprisingly, the merocyanine crystals so achieved have excellent purity and improved transmittance values ​​at 460 nm (preferably greater than 90%). DETAILED DESCRIPTION OF THE INVENTION

[0008] Thus, according to one embodiment, the present invention provides a compound of formula

[0009] [ka] (In the formula, R1 and R2 are independently hydrogen, C1 to C 22 -Alkyl, C2-C 22 -Alkenyl, C2-C 22 -Alkynyl, C3-C 22 -cycloalkyl or C3-C 22 -cycloalkenyl, wherein the foregoing moieties are optionally interrupted by one or more -O- and / or substituted by one or more OH; R3 is (C=O)OR4 or (C=O)NHR4; R4 is C1~C 22 -Alkyl, C2-C 22 -Alkenyl, C2-C 22 -Alkynyl, C3-C22 -cycloalkyl or C3-C 22 -cycloalkenyl, wherein the foregoing moieties are optionally substituted by one or more -OH and / or interrupted by one or more -O-; R5 and R6 are each independently hydrogen or C1-C 12 -alkyl) The present invention relates to an improved method for preparing crystalline merocyanine compounds of the formula (I).

[0010] In a further aspect, the present invention relates to crystals of merocyanine compounds obtainable by a process according to the inventive process for preparing crystalline merocyanine compounds as described herein.

[0011] In another aspect, the present invention relates to merocyanine compounds having a Gardner index of less than 5, measured according to DIN EN ISO 4630 on a PE Lambda 650 spectrophotometer.

[0012] In another aspect, the present invention relates to a method for reducing the residual level of colored impurities in a merocyanine compound by the methods as described herein.

[0013] In a further aspect, the present invention relates to the use of crystals obtainable by a process according to the inventive process for preparing a crystalline merocyanine compound as described herein in cosmetic formulations or packaging.

[0014] The merocyanine compounds of formula (1) are illustratively prepared by reacting a solution of 1-aminocyclohexanone-3 of formula (2) (wherein R, R, R, and R are defined as in formula (1)) with dimethyl sulfate or another suitable alkylating agent, followed by reaction with a suitable methylene-activated compound of formula (3) (wherein R is defined as in formula (1)), as described, for example, in U.S. Pat. No. 4,749,643, WO 2007 / 071582 A1, WO 2009 / 027258 A2, or IP-COM000225139D.

[0015] [ka]

[0016] The crude merocyanine product represented by formula (1) can be obtained from the reaction mixture by standard product isolation procedures, such as liquid-liquid separation, filtration, column chromatography, crystallization by cooling, crystallization by adding an anti-solvent to the reaction mixture, crystallization by distillation, or a combination of these isolation methods.

[0017] Before describing exemplary embodiments of the present invention in detail, definitions important for understanding the present invention are provided.

[0018] As used in this specification and the appended claims, the singular forms "a" and "an" also include the respective plural forms unless the context clearly dictates otherwise. In the context of the present invention, the term "about" denotes an interval of accuracy that a person skilled in the art would understand to still ensure the technical effect of the feature in question. The term typically indicates a deviation of ±20%, preferably ±15%, more preferably ±10%, and even more preferably ±5% from the indicated numerical value. The term "comprising" should be understood as non-limiting. For purposes of the present invention, the term "consisting of" is considered a preferred embodiment of the term "comprising of." Hereinafter, when a group is defined to include at least a certain number of embodiments, this also preferably encompasses a group consisting only of these embodiments. Furthermore, in the specification and claims, terms such as "first," "second," "third," or "(a)," "(b)," "(c)," "(d)," etc. are used to distinguish between similar elements and not necessarily to describe a sequential or chronological order. It is understood that terms so used are interchangeable under appropriate circumstances, and that the embodiments of the invention described herein are capable of operation in sequences other than those described or illustrated herein. When terms such as "first," "second," "third," or "(a)," "(b)," "(c)," "(d)," "(i)," "(ii)," and the like refer to steps in a method, use, or analysis, there is no time coherence or time interval coherence between the steps. That is, unless otherwise indicated herein above or in the following applications, steps may be performed simultaneously, or there may be time intervals of seconds, minutes, hours, days, weeks, months, or even years between such steps. It is understood that the invention is not limited to the particular methodologies, protocols, reagents, etc. described herein, as these may vary. It is further understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the invention, which is limited solely by the appended claims.Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

[0019] The terms "crude merocyanine product" and "crude merocyanine material" refer to the merocyanine compound added in step (a) of the method for preparing a crystalline merocyanine compound, and therefore refer to the merocyanine compound obtained, for example, via a multi-step sequence, before the crystallization method according to the present invention is carried out. Before carrying out the crystallization method according to the present invention, the crude merocyanine product may be purified by any other possible purification method after the multi-step sequence synthesis. However, the crystallization method according to the present invention may also be carried out directly after obtaining the crude merocyanine product after the multi-step sequence synthesis, without using any conventional purification method.

[0020] The term "crystallization mixture" refers to the total weight percent (wt%) mixture including all components at a particular step of the process.

[0021] The organic moieties mentioned in the above variable definitions are collective names to list the individual group members separately. n ~C m indicates in each case the possible number of carbon atoms in the group.

[0022] With regard to the variables, particularly preferred embodiments of the merocyanine compounds correspond to those of the compounds of formula (1).

[0023] The variables of the compounds of formula (1) have the following meanings, which meanings, by themselves or in combination with each other, represent the formula

[0024] [ka] (In the formula, R1 and R2 are independently hydrogen, C1 to C 22 -Alkyl, C2-C 22 -Alkenyl, C2-C 22-Alkynyl, C3-C 22 -cycloalkyl or C3-C 22 -cycloalkenyl, wherein the foregoing moieties are optionally interrupted by one or more -O- and / or substituted by one or more OH; R3 is (C=O)OR4 or (C=O)NHR4; R4 is C1~C 22 -Alkyl, C2-C 22 -Alkenyl, C2-C 22 -Alkynyl, C3-C 22 -cycloalkyl or C3-C 22 -cycloalkenyl, wherein the foregoing moieties are optionally substituted by one or more -OH and / or interrupted by one or more -O-; R5 and R6 are each independently hydrogen or C1-C 12 -alkyl) is a preferred embodiment of the compound

[0025] "C1~C 22 The term "-alkyl" as used herein denotes in each case a straight-chain or branched alkyl group, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, 2-pentyl, 3-pentyl, 2,2-dimethylpropyl, n-hexyl, n-octyl, 1,1,3,3-tetra-methylbutyl, 2-ethylhexyl, nonyl, decyl, n-octadecyl, eicosyl, or dodecyl.

[0026] "C2~C 22 The term "-alkenyl" as used herein refers in each case to a linear or branched alkenyl group having at least one singly unsaturated hydrocarbon radical, i.e., a hydrocarbon radical having at least one carbon-carbon double bond, such as a linear C-C 12 -alkenyl, or preferably branched C-C 12Other examples are vinyl, allyl, 2-propen-2-yl, 2-buten-1-yl, 3-buten-1-yl, 1,3-butadien-2-yl, 2-cyclobuten-1-yl, 2-penten-1-yl, 3-penten-2-yl, 2-methyl-1-buten-3-yl, 2-methyl-3-buten-2-yl, 3-methyl-2-buten-1-yl, 1,4-pentadien-3-yl, 2-cyclopenten-1-yl, 2- C1-C, such as cyclohexen-1-yl, 3-cyclohexen-1-yl, 2,4-cyclohexadien-1-yl, 1-p-menthen-8-yl, 4(10)-thujen-10-yl, 2-norbornen-1-yl, 2,5-norbornadien-1-yl, 7,7-dimethyl-2,4-norcaradien-3-yl, or the different isomers of hexenyl, octenyl, nonenyl, decenyl, or dodekenyl. 12 - alkyl.

[0027] "C2~C 22 The term "alkynyl" as used herein, in each case, denotes a hydrocarbon group having at least one carbon-carbon triple bond, and the chain may be a straight or branched alkynyl group, such as ethynyl, propargyl (also called 2-propyn-1-yl, prop-2-yn-1-yl), 1-propyn-1-yl (also called prop-1-yn-1-yl), 1-methylprop-2-yn-1-yl, 2-butyn-1-yl, 3-butyn-1-yl, 1-pentyn-1-yl, 3-pentyn-1-yl, 4-pentyn-1-yl, 1-methylbut-2-yn-1-yl, 1-ethylprop-2-yn-1-yl, etc.

[0028] "C3~C 22 The term "-cycloalkyl" as used herein denotes in each case a mono- or polycyclic alicyclic group, such as cyclopropyl, cyclobutyl, cyclopentyl, trimethylcyclohexyl, or preferably cyclohexyl.

[0029] "C3~C 22The term "-cycloalkenyl" as used herein denotes in each case a monocyclic or polycyclic monovalent unsaturated non-aromatic group. A cycloalkenyl group may be attached to the rest of the molecule through a carbon atom that forms a double bond or through a carbon atom that forms a single bond, preferably through a carbon atom that forms a double bond. Exemplary cycloalkenyl groups include cyclopropen-1-yl, cyclohexen-1-yl, cyclohepten-1-yl, or cycloocten-1-yl.

[0030] The term "interrupted by one or more -O-" preferably refers to any ether group, for example methoxyethyl, ethoxypropyl, 2-ethoxyethyl, 3-methoxypropyl, 2-butoxyethyl, or 2-(2-methoxyethoxy)ethyl.

[0031] The term "substituted by one or more OH" preferably refers to "hydroxy-substituted alkyl", such as hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, hydroxypentyl, hydroxyhexyl, hydroxyheptyl, hydroxyoctyl, hydroxynonyl, or hydroxydecyl.

[0032] The term "aliphatic" refers to any non-aromatic hydrocarbon group, wherein the constituent carbon atoms may be straight, branched, or cyclic, and / or heteroatoms may be attached to the carbon chain. Further, these aliphatic groups may be substituted with one or more of the same or different substituents.

[0033] In the sense of the present invention, the term "high purity" refers to a compound having a purity of at least 90% by weight, preferably at least 95% by weight, more preferably at least 97% by weight, based on the total weight of the final purified product, the remaining % by weight corresponding to impurities.

[0034] The merocyanine compounds of the present invention may be in the form of E,E-, E,Z-, or Z,Z-geometric isomers.

[0035] In one embodiment, the present invention relates to a method for preparing crystalline merocyanine compounds of formula (1), illustrated below and abbreviated as MC01-MC10, M15, and M27.

[0036] Examples of merocyanines according to the present invention are listed in Table A:

[0037] [Table 1]

[0038] The most preferred merocyanine derivatives of the present invention are selected from the group of the following compounds and their E,E-, E,Z-, or Z,Z-geometric isomeric forms:

[0039] [ka]

[0040] According to one particular embodiment of the invention, the merocyanine compound is 2-ethoxyethyl (2Z)-cyano{3-[(3-methoxypropyl)amino]cyclohex-2-en-1-ylidene}ethanoate.

[0041] According to one embodiment of the present invention, the merocyanine compound is provided in step (a) at a concentration ranging from about 50 to about 600 g / L, preferably from about 100 to about 580 g / L, and more preferably from about 200 to about 550 g / L.

[0042] The weight ratio of the organic polar solvent to the acid A1 and / or A2 is about 500:1 to about 0.5:1, preferably about 400:1 to about 0.8:1, more preferably about 350:1 to about 1:1.

[0043] In accordance with the present invention, a method for preparing a crystalline merocyanine compound comprises: (a) dissolving a merocyanine compound in an organic polar solvent; (b) crystallizing the merocyanine compound from the solution obtained in step (a); and (c) isolating the merocyanine compound from the crystallization mixture of step (b). Including, wherein the method is carried out at a pH of less than 7.

[0044] In step (a), the merocyanine compound (i.e., the crude merocyanine product) is dissolved in an organic polar solvent. According to one embodiment of the present invention, the organic solvent is selected from the group consisting of esters, ketones, ethers, alcohols, and mixtures thereof.

[0045] Suitable ester solvents may be methyl formate, ethyl formate, butyl formate, isobutyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, sec-butyl acetate, amyl acetate, isoamyl acetate, 2-ethylhexyl acetate, octyl acetate, nonyl acetate, hexyl acetate, ethoxypropyl acetate, propionate, ethyl 3-ethoxypropionate, butyrate, butyl butyrate, ethyl lactate, butyl lactate, butyl glycolate, and dimethyl adipate, or a mixture thereof. Preferably, an ester solvent selected from formate, acetate, or propionate solvents is used.

[0046] Also suitable are ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl isobutyl ketone, methyl amyl ketone, ethyl amyl ketone, dipropyl ketone, diisopropyl ketone, diisobutyl ketone, mesityl oxide, cyclohexanone, methylcyclohexanone, isophorone, or mixtures thereof.

[0047] Ether solvents such as diethyl ether, diisopropyl ether, dibutyl ether, di-sec-butyl ether, methyl tert-butyl ether, tetrahydrofuran, 1,4-dioxane, metadioxane, and glycol ethers such as methyl glycol, 2-ethoxyethanol, 2-propoxyethanol, 2-butoxyethanol, methyl diglycol, butyl diglycol, ethyl glycol, ethyl triglycol, butyl tetraglycol, diethylene glycol dimethyl ether, butyl triglycol, methoxypropanol, isobutoxypropanol, methyl dipropylene glycol, methoxybutanol, and 1,1-dimethoxyethane are suitable.

[0048] Suitable alcohol solvents may be methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, tert-butanol, pentanol, amyl alcohol, isoamyl alcohol, hexanol, 2-ethylhexanol, benzyl alcohol, cyclohexanol, methylcyclohexanol, furfuryl alcohol, tetrahydrofurfuryl alcohol, diacetone alcohol, or mixtures thereof. Preferably, isopropanol, sec-butanol, tert-butanol, tert-amyl alcohol, tert-octyl alcohol, or mixtures thereof are used.

[0049] In a preferred embodiment, the organic polar solvent is selected from the group consisting of diisopropyl ether, methyl isobutyl ketone, butyl acetate, isobutyl acetate, n-propyl acetate, isoamyl acetate, ethyl 3-ethoxypropionate, ethyl propionate, 1-methoxy-2-propanol, and mixtures thereof.

[0050] The temperature of the solution obtained in step (a) may range from about 0°C up to the boiling point of the solvent or solvent mixture used in this step, preferably from about 20°C to 100°C, most preferably from 30°C to 80°C.

[0051] In one embodiment, the crude merocyanine product may be first melted and then dissolved in the organic polar solvent. In this regard, the melt typically must first be cooled before the organic polar solvent is added.

[0052] In some cases, it may be advantageous to add the acid A1 in step (a) of the process. Thus, the acid A1 may be added to the organic polar solvent before or after dissolving the merocyanine compound.

[0053] In other cases, it may be advantageous to add acid A2 at any other stage of the crystallization process, for example, in step (b). Acid A2 may illustratively be added to the crystallizing mixture obtained in step (a) after cooling, after seeding the crude merocyanine solution, or during crystallization.

[0054] In other cases, it may be convenient to add acid A1 in process step (a) and acid A2 in process step (b), whereby acid A1 may be added before or after dissolving the merocyanine compound in the organic polar solvent, and acid A2 may be added to the crystallizing mixture after cooling the crystallization mixture obtained in step (a), after seeding the crude merocyanine solution, or during crystallization.

[0055] The step of inducing crystallization of the merocyanine compound from the solution obtained in step (a) may be achieved by any common crystallization method, such as adding a solvent in which the merocyanine compound is poorly soluble to the crystallization mixture, cooling the crystallization mixture, evaporating the solvent from the crystallization mixture, adding seeding crystals of the merocyanine compound to the crystallization mixture, or a combination thereof.

[0056] In one embodiment of the present invention, the crystallization of the merocyanine compound from the crystallization mixture comprises: - cooling the crystallization mixture; - adding seed crystals of a merocyanine compound to the crystallization mixture, and / or - Adding acid A2 Caused by

[0057] The temperature applied in step (b) may range from about -10°C to below the boiling point of the crystallization mixture, preferably from about -5°C to 100°C, more preferably from -5°C to 70°C.

[0058] Seeding may be performed by adding seed crystals, which may be added by any known method. For example, the seed crystals may be added while stirring the crystallization mixture. Generally, the amount of seed crystals added to the crystallization mixture ranges from about 0.01 wt % to about 2 wt %, preferably from about 0.05 wt % to about 1.8 wt %, based on the total weight of the crystallization mixture.

[0059] According to the invention, the acid A1 and / or the acid A2 can be selected from the following options: (i) adding an acid A1 in step (a), (ii) adding an acid A2 in step (b), or (iii) adding acid A1 in step (a) and acid A2 in step (b) so that the pH of the crystallization mixture is less than 7.

[0060] According to the present invention, any suitable acid can be used as acid A1 and acid A2. According to the present invention, acid A1 and acid A2 are independently selected from the group consisting of organic acids, inorganic acids, and mixtures thereof, and can be used in any suitable amount. Preferably, acid A1 and acid A2 are independently selected from the group consisting of acetic acid, aspartic acid, benzoic acid, boric acid, bromic acid, hydrochloric acid, citric acid, formic acid, gluconic acid, glutamic acid, hydrochloric acid, lactic acid, malic acid, nitric acid, sulfamic acid, sulfuric acid, methanesulfonic acid, toluenesulfonic acid, tartaric acid, phosphoric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and mixtures thereof. Preferably, hydrochloric acid, formic acid, or acetic acid is used. Sulfonic acids such as methanesulfonic acid are even more preferred.

[0061] In one particular embodiment, acid A1 is formic acid and acid A2 is methanesulfonic acid.

[0062] In one embodiment of the present invention, the method is carried out according to option (i). Accordingly, acid A1 is added in step (a). In one particular embodiment, the method is carried out according to option (i), and the organic polar solvent is preferably an ester.

[0063] In another embodiment of the invention, the process is carried out according to option (ii) or (iii), whereby acid A2 is added in step (b), or acid A1 is added in step (a) and acid A2 is added in step (b).

[0064] The total amount of acids A1 and / or A2 is in the range of 0.001% to 50% by weight, preferably 0.01% to 20% by weight, even more preferably 0.10% to 10% by weight, based on the total weight of the crystallization mixture.

[0065] Step (b) may be carried out with stirring. Stirring may be carried out during crystallization, provided that the stirring is carried out in a manner that does not interfere with the crystallization process.

[0066] When crystallization occurs, the stirring time may be varied and may be in the range of 2 to 30 hours, preferably 4 to 20 hours, and even more preferably 5 to 15 hours.

[0067] In certain embodiments, the present invention relates to a method in which step (a) of dissolving a merocyanine compound in an organic polar solvent is carried out by heating the mixture to its boiling point, and step (b) of crystallizing the merocyanine compound from the solution obtained in step (a) is carried out by cooling the crystallization mixture to a temperature within the range of −10° C. to below the boiling point of the crystallization mixture.

[0068] In another particular embodiment, the present invention relates to a method wherein step (a) of dissolving a merocyanine compound in an organic polar solvent is carried out by heating the mixture to boiling point, and step (b) of crystallizing the merocyanine compound from the solution obtained in step (a) is carried out by seeding the crystallization mixture comprising the crude merocyanine solution.

[0069] In another particular embodiment, the present invention relates to a method in which step (a) of dissolving a merocyanine compound in an organic polar solvent is carried out by heating the mixture to its boiling point, and step (b) of crystallizing the merocyanine compound from the solution obtained in step (a) is carried out by cooling the crystallization mixture to a temperature within the range of −10° C. to below the boiling point of the crystallization mixture, and additionally seeding the crystallization mixture with the crude merocyanine solution.

[0070] In step (c), the crystalline merocyanine compound may be isolated from the mixture by any conventional method, such as filtration, centrifugation, or evaporation of the solvent. Isolation by filtration or centrifugation is preferred.

[0071] The present invention provides for the reduction of residual levels of colored impurities in merocyanine compounds by the methods described herein.

[0072] Typically, the obtained merocyanine compound crystals, after isolation in step (c), are dried in optional step (d). Drying can be carried out by any known method, such as washing with a solvent, drying at room temperature or any higher temperature, freeze-drying, under vacuum, etc. It is preferred to dry the material obtained in step (c) under vacuum at a temperature above 50°C.

[0073] In certain embodiments, the present invention relates to the aforementioned method, wherein the crystalline merocyanine compound has a Gardner index of less than 5, preferably less than 3.2, measured according to DIN EN ISO 4630 on a PE (PerkinElmer) Lambda 650 spectrophotometer.

[0074] The present invention further relates to crystals of merocyanine compounds obtainable by the process of the present invention.

[0075] In one embodiment, the crystalline merocyanine compound obtainable by the process of the present invention has a Gardner index of less than 5, preferably less than 3.2, measured according to DIN EN ISO 4630 on a PE (PerkinElmer) Lambda 650 spectrophotometer. In another embodiment, the crystalline merocyanine compound obtainable by the process of the present invention has a transmittance value at 460 nm of more than 90%. In a particular embodiment of the present invention, the crystalline merocyanine compound obtainable by the process of the present invention has a Gardner index of less than 5, preferably less than 3.2, measured according to DIN EN ISO 4630 on a PE (PerkinElmer) Lambda 650 spectrophotometer, and a transmittance value at 460 nm of more than 90%.

[0076] The obtained crystals of the merocyanine compound more preferably have a higher purity.

[0077] The merocyanine compound crystals obtained by the method of the present invention exhibit low discoloration properties. To compare the merocyanine compound crystals with crude merocyanine products, the Gardner index and percent transmittance at a wavelength of 460 nm can be measured. The merocyanine compound crystals obtained by the method of the present invention exhibit significantly lower Gardner indices, typically less than 3.2 and desirably less than 3.0 for many applications. In contrast, crude merocyanine materials exhibit Gardner indices greater than 5.

[0078] The determined % transmittance values ​​of the crystalline merocyanine compound obtained by the method of the present invention, measured at a wavelength of 460 nm, are significantly higher than those of the crude merocyanine material, indicating lower absorption characteristics in the visible region of light. The crystalline merocyanine compound according to the present invention exhibits % transmittance values ​​of 90% or more at 460 nm, while the crude merocyanine material typically has a value of 10% or less.

[0079] In one embodiment, the present invention provides a compound of formula

[0080] [ka] (In the formula, R1 and R2 are independently hydrogen, C1 to C 22 -Alkyl, C2-C 22 -Alkenyl, C2-C 22 -Alkynyl, C3-C 22 -cycloalkyl or C3-C 22 -cycloalkenyl, wherein the foregoing moieties are optionally interrupted by one or more -O- and / or substituted by one or more OH; R3 is (C=O)OR4 or (C=O)NHR4; R4 is C1~C 22 -Alkyl, C2-C 22 -Alkenyl, C2-C 22 -Alkynyl, C3-C 22 -cycloalkyl or C3-C 22 -cycloalkenyl, wherein the foregoing moieties are optionally substituted by one or more -OH and / or interrupted by one or more -O-; R5 and R6 are each independently hydrogen or C1-C 12 -alkyl) A crystalline merocyanine compound of the formula: The crystalline merocyanine compounds relate to crystalline merocyanine compounds having a Gardner index, measured in accordance with DIN EN ISO 4630 on a PE Lambda 650 spectrophotometer, of less than 5, preferably less than 3.2.

[0081] In another embodiment, the present invention provides a compound of formula

[0082] [ka] (In the formula, R1 and R2 are independently hydrogen, C1 to C 22 -Alkyl, C2-C 22-Alkenyl, C2-C 22 -Alkynyl, C3-C 22 -cycloalkyl or C3-C 22 -cycloalkenyl, wherein the foregoing moieties are optionally interrupted by one or more -O- and / or substituted by one or more OH; R3 is (C=O)OR4 or (C=O)NHR4; R4 is C1~C 22 -Alkyl, C2-C 22 -Alkenyl, C2-C 22 -Alkynyl, C3-C 22 -cycloalkyl or C3-C 22 -cycloalkenyl, wherein the foregoing moieties are optionally substituted by one or more -OH and / or interrupted by one or more -O-; R5 and R6 are each independently hydrogen or C1-C 12 -alkyl) A crystalline merocyanine compound of the formula: The crystalline merocyanine compound relates to a crystalline merocyanine compound having a transmittance value at 460 nm of greater than 90%.

[0083] In yet another embodiment, the present invention provides a compound of formula

[0084] [ka] (In the formula, R1 and R2 are independently hydrogen, C1 to C 22 -Alkyl, C2-C 22 -Alkenyl, C2-C 22 -Alkynyl, C3-C 22 -cycloalkyl or C3-C 22 -cycloalkenyl, wherein the foregoing moieties are optionally interrupted by one or more -O- and / or substituted by one or more OH; R3 is (C=O)OR4 or (C=O)NHR4; R4 is C1~C 22 -Alkyl, C2-C 22-Alkenyl, C2-C 22 -Alkynyl, C3-C 22 -cycloalkyl or C3-C 22 -cycloalkenyl, wherein the foregoing moieties are optionally substituted by one or more -OH and / or interrupted by one or more -O-; R5 and R6 are each independently hydrogen or C1-C 12 -alkyl) A crystalline merocyanine compound of the formula: The crystalline merocyanine compounds relate to crystalline merocyanine compounds having a Gardner index of less than 5, preferably less than 3.2, measured in accordance with DIN EN ISO 4630 on a PE Lambda 650 spectrophotometer, and a transmittance value at 460 nm of more than 90%.

[0085] The crystalline merocyanine compound of formula (1) more preferably has a higher purity.

[0086] The present invention further relates to the use of crystals of merocyanine compounds obtainable by the process of the present invention, and to the use of crystalline merocyanine compounds of formula (1) according to the present invention. In particular, the present invention relates to the use of merocyanine compounds obtainable by the process of the present invention in cosmetic formulations or packaging. Furthermore, the present invention relates to the use of crystalline merocyanine compounds of formula (1) according to the present invention in cosmetic formulations or packaging. Preferably, such compounds are used as UV absorbers.

[0087] The crystalline merocyanine compounds obtainable by the process according to the invention, and the crystalline merocyanine compounds of formula (1) according to the invention, can be mixed with any other UV absorbers.

[0088] In one embodiment, the crystals of the present invention are used as a single component or mixed with other UV absorbers in cosmetic formulations, such as skin care products, bath and shower additives, preparations containing fragrances and odoriferous substances, hair care products, dentifrices, deodorizing and antiperspirant preparations, decorative preparations, and light protection formulations.

[0089] The photoprotective formulations of the invention are, for example, sun milks, lotions, creams or oils, sunscreens or tropical, pre-tanning or after-sun preparations. In particular, the crystals are used in photoprotective formulations.

[0090] In one embodiment, the crystals of the present invention are used in packaging, preferably transparent packaging, as a single component or mixed with other UV absorbers, for example, in transparent packaging for food protection or pharmaceutical packaging applications.

[0091] In another embodiment, the crystals of the present invention are used in photographic recording materials, either as a single component or mixed with other UV absorbers.

[0092] Due to the improved UV-A and UV-B absorption properties of the crystals of the present invention, products packaged in the packaging of the present invention are advantageously protected from UV-A and UV-B rays.

[0093] Analysis method: Gardner Index Therefore, the Gardner index may usually be measured with a typical device. In the present invention, the Gardner index is measured according to DIN EN ISO 4630 with a spectrophotometer PE (PerkinElmer) Lambda 650.

[0094] HPLC standard method Liquid chromatography with DAD detection was performed. The column used was a Zorbax Eclipse XDB-C18 1.8μ, 4.6×100 mm (Agilent). Mobile phase A: water and 0.05% formic acid. Mobile phase B: acetonitrile and 0.05% formic acid. The standard HPLC gradients applied are shown in Table B.

[0095] [Table 2]

[0096] The flow rate was 0.7 ml / min, the injection volume was 3 μL, and the temperature was 47° C. Detection was performed at a wavelength of 230 nm.

[0097] % transmittance 460nm A Lamda 35 was used as spectrophotometer and a Polystat CC3 - Huber G3 as thermostat.

[0098] The following parameters were selected: Wavelength: 460nm Cell type: Quartz, 10 mm Measurement mode: Transmittance Number of cycles: 1 Response: 2 Lamps: 2 Slit: 2.00nm Temperature: 25℃ Test solution: 1.00% w / v in ethanol Reference: (Baseline / Reference Light): Use the corresponding blank solution Solvent: Ethanol - anhydrous denatured spectrophotometric grade, 90%, 5% methanol, 5% iso-propanol - Alfa Aesar Art.Nr. 22931

[0099] Approximately 50.0 mg of the corresponding sample was weighed into a 5.00 mL volumetric flask and filled to the mark with ethanol to give a 1% w / v solution in ethanol. If necessary, the sample was treated in an ultrasonic bath for 1-2 minutes.

[0100] purity Purity was determined by the HPLC standard method described above.

[0101] The present invention is further illustrated by the following examples. [Example]

[0102] Crystallization of merocyanine UV absorbers.

[0103] Comparative Example: Crystallization of the Compound of Formula MC03 Without Acid 30.0 g of compound MC03 (crude product with a Gardner index of 10.7 and a purity of 95.4%) was dissolved in 70.0 g of n-butyl acetate at 64°C. The mixture was cooled to 53°C with stirring, and then seeded with 0.16 g of crystalline compound MC03. The temperature was then lowered to 10°C over a period of 15.3 hours. The temperature of 10°C was maintained for 0.5 hours. The suspension was then transferred to a Buchner funnel, and the mother liquor was removed by suction. The filter cake was rinsed with 30.0 g of butyl acetate. 30.0 g of butyl acetate was then added, and the cake was reslurried in the washings using a spatula, and the washings were removed by suction. Finally, the crystals were rinsed with 30.0 g of butyl acetate. The crystals were then dried in a vacuum oven at 85°C and 20 mbar for 16 hours, yielding 25.1 g of pure product of formula MC03 (87.1% yield). Gardner index: 7.7, %T460nm: 2.4, purity: 98.8%.

[0104] Example 1: Crystallization of the compound of formula MC03 using formic acid and methanesulfonic acid in an ethereal solvent 50.0 g of compound MC03 (crude product with a Gardner index of 10.7 and a purity of 95.8%) was transferred to a dropping funnel equipped with a heating jacket. The jacket was heated to 120° C. until the crude product was completely melted. The funnel containing the crude product melt was placed at the bottom of the reaction vessel, equipped with an anchor impeller, a thermometer, a cooling jacket, and an outlet spindle.

[0105] 111.8 g of diisopropyl ether and 35.5 g of formic acid were added to a reactor and heated to 32°C with stirring. The crude product melt was added over a 15-minute period while maintaining the temperature of the mixture in the reactor at 32°C and the stirring speed at 350 rpm. Then, 0.64 g of methanesulfonic acid and 1.11 g of crystalline compound MC03 were added to the mixture. The stirring speed was reduced to 200 rpm, and the heating temperature was reduced from 30°C to 29°C over a 1-hour period. The cooling temperature was then linearly reduced to 19°C over a 240-minute period, and then reduced to -8°C over a 648-minute period, resulting in an internal temperature of -5°C. The -5°C internal temperature was maintained for 0.5 hours. The suspension was then transferred to a Büchner funnel, and the mother liquor was removed by suction. The filter cake was rinsed with 44.4 g of diisopropyl ether / formic acid (95:5). The filter cake was then washed with 133.2 g of diisopropyl ether in four portions, and the second portion was used to reslurry the cake in the washings and then suction-separated. The washed product crystals were dried in a vacuum oven at 65 ° C and 20 mbar for 16 hours to give 39.6 g of crystallized product (80.4% yield). Gardner index = 3.0, % T460nm: 93.3.

[0106] Example 2: Crystallization of the compound of formula MC03 using formic acid and methanesulfonic acid in ether solvent 26.1 g of compound MC03 (crude product with a Gardner index of 8.6 and a purity of 95.9%) was dissolved in 17.7 g of formic acid and 55.8 g of diisopropyl ether at 50°C, followed by the addition of 0.32 g of methanesulfonic acid. The mixture was cooled to 32°C with stirring, and then 1.25 g of compound MC03 was added. The cooling temperature was then lowered to -8°C over a period of 912 minutes. The -8°C cooling temperature was maintained for 0.5 hours. The suspension was then transferred to a Buchner funnel, and the mother liquor was removed by suction. The filter cake was rinsed with 50.0 g of diisopropyl ether / formic acid (95:5). The filter cake was then washed with 150.0 g of diisopropyl ether in four portions. The washed product crystals were dried in a vacuum oven at 65°C and 20 mbar for 16 hours to give 21.5 g of crystallized product (80.9% yield). Gardner index: 2.7, % T460nm: 96.1.

[0107] Example 3: Crystallization of the compound of formula MC03 using methanesulfonic acid in an ester solvent. 25.0 g of compound MC03 (crude product with a Gardner index of 10.6 and a purity of 95.3%) was dissolved in 75.0 g of butyl acetate at 54°C. After cooling to a temperature of 46°C, 0.30 g of methanesulfonic acid and 0.13 g of crystalline MC03 for seeding were added. The cooling temperature was then lowered to -8°C, and the temperature of the mixture was -5°C. The cooling temperature of -8°C was maintained for 0.5 hours. The crystals were then isolated by filtration and washed with 110.0 g of butyl acetate in three portions. The product crystals were then dried at 65°C and 20 mbar for 16 hours to obtain 20.0 g of a crystalline product of formula MC03 (yield 83.3%). Gardner index: 2.7, % T460nm: 98.2.

[0108] Example 4: Crystallization of the compound of formula MC03 using formic acid in an ester solvent. 20.0 g of compound MC03 (crude product with a Gardner index of 10.6 and a purity of 95.3%) was dissolved in 70.0 g of butyl acetate and 10.0 g of formic acid at 49 °C. After cooling to a temperature of 26 °C, 0.10 g of crystalline MC03 was added for seeding. The cooling temperature was then lowered to 7 °C, and the mixture temperature was brought to 10 °C. The cooling temperature of 7 °C was maintained for 0.5 hours. The crystals were then isolated by filtration and rinsed with 40.0 g of diisopropyl ether. 50.0 g of diisopropyl ether was then added, and the cake was reslurried in the washings using a spatula, and the washings were removed by suction. Finally, the crystals were rinsed with 50.0 g of diisopropyl ether. The crystals were then dried in a vacuum oven at 65 °C and 20 mbar for 64 hours, yielding 9.14 g of pure product (47.4% yield). Gardner index: 2.8, %T460nm: 97.9.

[0109] Example 5: Crystallization of the compound of formula MC03 using methanesulfonic acid in an ester solvent. 20.0 g of compound MC03 (crude product with a Gardner index of 10.6 and a purity of 95.3%) was dissolved in 80.0 g of n-propyl acetate at 55°C. After cooling to a temperature of 41°C, 0.24 g of methanesulfonic acid and 0.10 g of crystals of formula MC03 for seeding were added. The cooling temperature was then lowered to -8°C, and the temperature of the mixture was -5°C. The cooling temperature of -8°C was maintained for 0.5 hours. The crystals were then isolated by filtration and rinsed with 30.0 g of chilled n-propyl acetate (the temperature of the washings was 5°C). 40.0 g of chilled propyl acetate was then added, and the cake was reslurried in the washings using a spatula, and the washings were removed by suction. Finally, the crystals were rinsed with 40.0 g of chilled propyl acetate. The crystals were then dried in a vacuum oven at 65°C and 20 mbar for 64 hours to give 14.81 g of pure product (77.2% yield). Gardner index: 2.8, % T460nm: 97.4.

[0110] Example 6: Crystallization of the compound of formula MC03 using methanesulfonic acid in a ketone solvent 30.0 g of compound MC03 (crude product with a Gardner index of 10.7 and a purity of 95.4%) was dissolved in 70.0 g of methyl isobutyl ketone at 49 ° C. After cooling to a temperature of 43 ° C, 0.36 g of methanesulfonic acid and 0.16 g of MC03 crystals for seeding were added. The cooling temperature was then lowered to 7 ° C, and the mixture temperature was brought to 11 ° C. The cooling temperature of 7 ° C was maintained for 0.5 hours. The crystals were then isolated by filtration using a Buchner funnel equipped with filter paper and rinsed with 30.0 g of chilled methyl isobutyl ketone (the temperature of the washings was 14 ° C). 30.0 g of methyl isobutyl ketone was then added, and the cake was reslurried in the washings using a spatula, and the washings were removed by suction. Finally, the crystals were rinsed with 30.0 g of chilled methyl isobutyl ketone. The crystals were then dried in a vacuum oven at 70°C and 20 mbar for 2 hours, then at 80°C and 20 mbar for 16 hours to give 17.8 g of pure product (61.6% yield). Gardner index: 2.9, %T460nm: 96.9.

[0111] Example 7: Crystallization of the compound of formula MC03 using methanesulfonic acid in an ester solvent. 30.0 g of compound MC03 (crude product with a Gardner index of 10.7 and a purity of 95.4%) was dissolved in 70.0 g of isoamyl acetate at 68 ° C. After cooling to a temperature of 58 ° C, 0.36 g of methanesulfonic acid and 0.16 g of MC03 crystals for seeding were added. The cooling temperature was then reduced to 7 ° C over a period of 17 hours, and the temperature of the mixture was brought to 10 ° C. The cooling temperature of 7 ° C was maintained for 0.5 hours. The crystals were then isolated by filtration using a Buchner funnel equipped with filter paper and rinsed with 30.0 g of chilled isoamyl acetate (the temperature of the washings was 14 ° C). 30.0 g of chilled isoamyl acetate was then added, and the cake was reslurried in the washings using a spatula, and the washings were removed by suction. Finally, the crystals were rinsed with 30.0 g of chilled isoamyl acetate. The crystals were then dried in a vacuum oven at 70°C and 20 mbar for 2 hours, then at 85°C and 20 mbar for 16 hours to give 26.0 g of pure product (90.2% yield). Gardner index: 2.9, % T460nm: 96.3.

[0112] Example 8: Crystallization of the compound of formula MC03 using methanesulfonic acid in an ester solvent. 36.0 g of compound MC03 (crude product with a Gardner index of 10.7 and a purity of 95.4%) was dissolved in 60.0 g of ethyl 3-ethoxypropionate at 64°C. After cooling to a temperature of 52°C, a solution of 0.41 g of methanesulfonic acid in 3.00 g of ethyl 3-ethoxypropionate was added via a funnel, followed by rinsing with 1.00 g of ethyl 3-ethoxypropionate. The temperature was then lowered to 50°C, and 0.18 g of MC03 crystals were added for seeding. The cooling temperature was then lowered to -1°C over a period of 17 hours, and the mixture temperature reached 5°C. The cooling temperature of -1°C was maintained for 1 hour. The crystals were then isolated by filtration using a Buchner funnel equipped with filter paper, and the mother liquor was removed by suction. The filter cake was then rinsed with 40.0 g of mother liquor (the temperature of the rinse was 9°C). Then, 30.0 g of chilled ethyl 3-ethoxypropionate was added (the temperature of the washings was 9°C), and the cake was reslurried in the washings using a spatula, and the washings were removed by suction. Finally, the crystals were rinsed with 30.0 g of chilled ethyl 3-ethoxypropionate. The crystals were then dried in a vacuum oven at 85°C and 20 mbar for 64 hours, yielding 29.9 g of pure product (86.6% yield). Gardner index: 2.9, % T460nm: 95.3, purity: 98.1%.

[0113] Example 9: Crystallization of the compound of formula MC03 using methanesulfonic acid in an ester solvent. 38.0 g of compound MC03 (crude product with a Gardner index of 10.7 and a purity of 95.4%) was dissolved in 62.0 g of isobutyl acetate at 75°C. After cooling to a temperature of 54°C, 0.385 g of methanesulfonic acid and 0.18 g of MC03 crystals for seeding were added. The cooling temperature was then reduced to 5°C over a period of 16.3 hours, and the mixture temperature was brought to 10°C. The cooling temperature of 5°C was maintained for 3 hours. The crystals were then isolated by filtration using a Buchner funnel equipped with filter paper, and the mother liquor was removed by suction. The filter cake was then rinsed with 40.0 g of mother liquor (the temperature of the washings was 11°C). 30.0 g of cooled isobutyl acetate was then added (the temperature of the washings was 10°C), and the cake was reslurried in the washings using a spatula, and the washings were removed by suction. Finally, the crystals were rinsed with 30.0 g of chilled isobutyl acetate. They were then dried in a vacuum oven at 85 °C and 20 mbar for 16 h, yielding 33.4 g of pure product (91.6% yield). Gardner index: 2.9, % T460nm: 96.0.

[0114] Example 10: Crystallization of the compound of formula MC03 using methanesulfonic acid in an ester solvent. 34.0 g of compound MC03 (crude product with a Gardner index of 10.7 and a purity of 95.4%) was dissolved in 63.0 g of ethyl propionate and 0.7 g of toluene at 65°C. After cooling to a temperature of 46°C, 0.385 g of methanesulfonic acid dissolved in 2.0 g of ethyl propionate was added via the funnel, and the funnel was then rinsed with 1.0 g of ethyl propionate. After seeding the mixture with 0.18 g of MC03 crystals, the cooling temperature was reduced to 40°C over 3 hours, then to 20°C over 5 hours, and finally to 0°C over 4 hours, bringing the final mixture temperature to 5°C. The cooling temperature of 5°C was maintained for 0.5 hours. The crystals were then isolated by filtration using a Buchner funnel equipped with filter paper, and the mother liquor was removed by suction. The filter cake was then rinsed with 40.0 g of mother liquor (the temperature of the wash was 9°C). 30.0 g of chilled ethyl propionate was then added (the temperature of the wash was 9°C), and the cake was reslurried in the wash using a spatula, and the wash was removed by suction. Finally, the crystals were rinsed with 30.0 g of chilled ethyl propionate. The crystals were then dried in a vacuum oven at 85°C and 20 mbar for 16 hours, yielding 27.7 g of pure product (84.9% yield). Gardner index: 2.7, % T460nm: 97.5, purity: 98.0%.

[0115] Example 11: Crystallization of the compound of formula MC03 using methanesulfonic acid in an alcohol solvent 30.0 g of compound MC03 (crude product with a Gardner index of 10.7 and a purity of 95.4%) was dissolved in 70.0 g of 1-methoxy-2-propanol at 60°C. After cooling to a temperature of 36°C, 0.36 g of methanesulfonic acid and 0.16 g of MC03 crystals for seeding were added. The cooling temperature was reduced to 7°C over a period of 9.7 hours, and the temperature of the final mixture was 10°C. The cooling temperature of 7°C was maintained for 0.5 hours. The crystals were then isolated by filtration using a Buchner funnel equipped with filter paper, and the mother liquor was removed by suction. The filter cake was then rinsed with 30.0 g of chilled 1-methoxy-2-propanol (the temperature of the washings was 14°C). Then, 30.0 g of chilled 1-methoxy-2-propanol was added (the temperature of the washings was 14°C), and the cake was reslurried in the washings using a spatula, and the washings were removed by suction. Finally, the crystals were rinsed with 30.0 g of chilled 1-methoxy-2-propanol. The crystals were then dried in a vacuum oven at 85°C and 20 mbar for 16 hours, yielding 12.0 g of pure product (41.5% yield). Gardner index: 2.8, % T460nm: 97.4.

[0116] A comparison of the color properties, transmittance at 460 nm, and purity of the crystallized merocyanine compounds of the present invention (Examples 1-11) with a reference merocyanine crystallized in the absence of acid (Comparative Example) is listed in Table C:

[0117] [Table 3]

[0118] The crystallized merocyanine compounds of the comparative examples, crystallized in an organic polar solvent in the absence of acid, exhibit significantly higher yellowing properties as indicated by high Gardner indices of greater than 5 and low % transmittance values ​​at 460 nm of less than 10. In contrast, the merocyanine compounds of Examples 1-11, crystallized in accordance with the present invention in the presence of acid, exhibit significantly better color properties as indicated by low Gardner indices of less than 3.2 and high % transmittance values ​​at 460 nm of greater than 90%.

Claims

1. 1. A method for preparing a crystalline merocyanine compound, comprising: (a) dissolving a merocyanine compound in an organic polar solvent; (b) crystallizing the merocyanine compound from the solution obtained in step (a); and (c) isolating the merocyanine compound from the crystallization mixture of step (b). Including the following options: (i) adding an acid A1 in step (a), (ii) adding an acid A2 in step (b), or (iii) adding acid A1 in step (a) and acid A2 in step (b) The method is carried out at a pH of less than 7 according to

2. The merocyanine compound is represented by the formula (1) 【Chemical 1】 (In the formula, R 1 and R 2 are, independently of each other, hydrogen, C 1 ~C 22 -Alkyl, C 2 ~C 22 -Alkenyl, C 2 ~C 22 -alkynyl, C 3 ~C 22 -cycloalkyl, or C 3 ~C 22 -cycloalkenyl, wherein the foregoing moieties are optionally interrupted by one or more -O- and / or substituted by one or more OH; R 3 is (C=O)OR 4 or (C=O)NHR 4 and R 4 is C 1 ~C 22 -Alkyl, C 2 ~C 22 -Alkenyl, C 2 ~C 22 -alkynyl, C 3 ~C 22 -cycloalkyl, or C 3 ~C 22 -cycloalkenyl, wherein the foregoing moieties are optionally substituted by one or more -OH and / or interrupted by one or more -O-; R 5 and R 6 are, independently of each other, hydrogen or C 1 ~C 12 -alkyl) The method of claim 1, represented by:

3. 3. The method of claim 1 or 2, wherein the merocyanine compound is provided in step (a) at a concentration ranging from about 50 to about 600 g / L.

4. the organic polar solvent is selected from the group consisting of esters, ketones, ethers, alcohols, and mixtures thereof; 4. The method according to any one of claims 1 to 3, wherein the organic polar solvent is selected from the group consisting of diisopropyl ether, methyl isobutyl ketone, butyl acetate, isobutyl acetate, n-propyl acetate, isoamyl acetate, ethyl 3-ethoxypropionate, ethyl propionate, 1-methoxy-2-propanol, and mixtures thereof.

5. crystallizing the merocyanine compound from the crystallization mixture, - cooling the crystallization mixture; - adding seed crystals of said merocyanine compound to said crystallization mixture; and / or - Adding acid A2 The method according to any one of claims 1 to 4, wherein the method is caused by

6. the acid A1 and the acid A2 are independently selected from the group consisting of organic acids, inorganic acids, and mixtures thereof; 6. The method according to any one of claims 1 to 5, wherein the acid A1 and the acid A2 are independently selected from the group consisting of acetic acid, aspartic acid, benzoic acid, boric acid, bromic acid, hydrochloric acid, citric acid, formic acid, gluconic acid, glutamic acid, lactic acid, malic acid, nitric acid, sulfamic acid, sulfuric acid, methanesulfonic acid, toluenesulfonic acid, tartaric acid, phosphoric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and mixtures thereof.

7. the acid A1 is formic acid, 7. The method according to any one of claims 1 to 6, wherein the acid A2 is methanesulfonic acid.

8. 8. The method according to any one of claims 1 to 7, carried out according to option (ii) or (iii).

9. 8. The method according to any one of claims 1 to 7, wherein the method is carried out according to option (i), and the organic polar solvent is preferably an ester.

10. 10. The method according to any one of claims 1 to 9, wherein the total amount of acids A1 and / or A2 is in the range of 0.001% to 50% by weight, based on the total weight of the crystallization mixture.

11. the step (a) of dissolving the merocyanine compound in the organic polar solvent is carried out by heating the mixture to a boiling point; 11. The method of claim 1, wherein step (b) of crystallizing the merocyanine compound from the solution obtained in step (a) is carried out by cooling the crystallization mixture to a temperature within a range of from −10° C. to below the boiling point of the crystallization mixture.

12. 12. The method according to any one of claims 1 to 11, wherein the crystalline merocyanine compound has a Gardner index of less than 5, preferably less than 3.2, measured in accordance with DIN EN ISO 4630 with a PE Lambda 650 spectrophotometer.

13. A crystal of a merocyanine compound obtainable by the method according to any one of claims 1 to 12.

14. 14. The crystal according to claim 13, having a Gardner index of less than 5, preferably less than 3.2, measured according to DIN EN ISO 4630 on a PE Lambda 650 spectrophotometer, and / or a transmittance value at 460 nm of more than 90%.

15. 15. Use of the crystals according to claim 13 or 14 in cosmetic formulations or packaging.

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