A preparation method of Michler's ketone derivative

Abstract

The present invention provides a method for preparing a Michler's ketone derivative, which belongs to the field of organic synthesis. A method for preparing a Michler's ketone derivative comprises the following steps: mixing bis(4-(dialkylamino)phenyl)methane, a catalyst, a 1-alkyl-3-methylimidazolium hydrogen sulfate ionic liquid, oxygen and water for an oxidation reaction to obtain the Michler's ketone derivative; the catalyst comprises 2,3,5,6-tetrachlorobenzoquinone and tert-butyl nitrite; the Michler's ketone derivative comprises the structural formula shown in Formula I; and R1 and R2 are independently C2 to C18 alkyl groups. The 1-alkyl-3-methylimidazolium hydrogen sulfate ionic liquid can promote the decomposition of tert-butyl nitrite into nitrogen oxides required for the oxidation reaction, thereby improving the selectivity and yield of the Michler's ketone derivative. At the same time, the use of the catalyst of the present invention to catalyze the oxidation reaction avoids the use of a transition metal catalyst and does not have the problem of metal residue; oxygen is used as an oxidant, which is environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the field of organic synthesis, and in particular to a method for preparing a Michler's ketone derivative. Background Art

[0002] With the rapid development of my country's economy, environmental pressures are gradually increasing. Reducing volatile substances in coatings and inks has become an inevitable trend. Ultraviolet (UV) curing technology is one of the measures to address this problem. UV curing technology is a photoprocessing process that uses ultraviolet light of a certain wavelength to rapidly polymerize liquid resin into a solid state. It utilizes the photosensitivity of a photoinitiator (photosensitizer). Under ultraviolet light, the photoinitiator forms excited molecules, which decompose into free radicals or ions, causing unsaturated organic compounds to undergo chemical reactions such as polymerization, grafting, and cross-linking, thereby achieving the purpose of curing.

[0003] Photoinitiators, also known as photosensitizers or photocuring agents, are a class of compounds that can absorb energy of a certain wavelength in the ultraviolet or visible light region to generate free radicals, cations, etc., thereby initiating monomer polymerization, cross-linking, and curing. They are the most critical components in the photocuring system. Depending on the different active intermediates produced by the photoinitiator, they can be divided into free radical photoinitiators and cationic photoinitiators. Among free radical photoinitiators, they are divided into cleavage photoinitiators (Norrish I type) and hydrogen abstraction photoinitiators (Norrish II type) according to the different mechanisms of action for generating active free radicals. Michler's ketone derivatives, namely bis(4-(dialkylamino)phenyl)methanone, are the most studied compounds among hydrogen abstraction photoinitiators. In its structure, the two tertiary amines connected to the benzene ring serve as hydrogen sources, so it exhibits good performance in initiating monomer polymerization and is widely used.

[0004] Michler's ketone derivatives can be obtained by direct oxidation of bis(4-(dialkylamino)phenyl)methane at the benzylic position. Oxygen oxidation with the participation of transition metals is usually used, but this can lead to the problem of residual transition metals in the product, thereby affecting the quality of the final UV-curable product. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing Michler's ketone derivatives. The Michler's ketone derivatives prepared by the present invention have good selectivity, high yield and no residual transition metal.

[0006] The present invention provides a method for preparing a Michler's ketone derivative, comprising the following steps:

[0007] Mixing bis(4-(dialkylamino)phenyl)methane, a catalyst, a 1-alkyl-3-methylimidazolium hydrogen sulfate ionic liquid, oxygen, and water to perform an oxidation reaction to obtain the Michler's ketone derivative;

[0008] The catalyst includes 2,3,5,6-tetrachlorobenzoquinone and tert-butyl nitrite;

[0009] The Michler's ketone derivatives include the structural formula shown in Formula I:

[0010] The R 1 and R 2 are independently C2-C18 alkyl groups.

[0011] Preferably, the molar ratio of 2,3,5,6-tetrachlorobenzoquinone to tert-butyl nitrite is 1:1-7.

[0012] Preferably, the bis(4-(dialkylamino)phenyl)methane has the structural formula shown in Formula I:

[0013]

[0014] Preferably, the molar ratio of 2,3,5,6-tetrachlorobenzoquinone to bis(4-(dialkylamino)phenyl)methane is 0.08-0.20:1.

[0015] Preferably, the 1-alkyl-3-methylimidazolium hydrogen sulfate ionic liquid includes one or more of 1-ethyl-3-methylimidazolium hydrogen sulfate, 1-butyl-3-methylimidazolium hydrogen sulfate, 1-propyl-3-methylimidazolium hydrogen sulfate and 1-hexyl-3-methylimidazolium hydrogen sulfate.

[0016] Preferably, the mass ratio of the 1-alkyl-3-methylimidazolium hydrogen sulfate ionic liquid to bis(4-(dialkylamino)phenyl)methane is 5 to 20:1.

[0017] Preferably, the molar ratio of water to bis(4-(dialkylamino)phenyl)methane is 0.01 to 0.1:1.

[0018] Preferably, the temperature of the oxidation reaction is 0-40° C., and the time is 8-16 hours.

[0019] Preferably, after the oxidation reaction, the method further comprises extracting the product obtained from the oxidation reaction, removing the extractant and performing column treatment to obtain a pure product of the Michler's ketone derivative.

[0020] Preferably, the extraction agent comprises toluene.

[0021] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0022] The present invention provides a method for preparing a Michler's ketone derivative, comprising the following steps: mixing bis(4-(dialkylamino)phenyl)methane, a catalyst, a 1-alkyl-3-methylimidazolium hydrogen sulfate ionic liquid, oxygen and water to carry out an oxidation reaction to obtain the Michler's ketone derivative;

[0023] The catalyst includes 2,3,5,6-tetrachlorobenzoquinone and tert-butyl nitrite;

[0024] The Michler's ketone derivatives include the structural formula shown in Formula I:

[0025] The R 1 and R 2 are independently C2-C18 alkyl groups.

[0026] The 1-alkyl-3-methylimidazolium hydrogen sulfate ionic liquid can promote the decomposition of tert-butyl nitrite into the substances required to catalyze the oxidation reaction, thereby improving the selectivity and yield of Michler's ketone derivatives. Furthermore, the use of the catalyst of the present invention in the oxidation reaction avoids the use of transition metal catalysts, eliminating the problem of metal residue. Oxygen is used as the oxidant, making it environmentally friendly. The 2,3,5,6-tetrachlorobenzoquinone dissolved in the 1-alkyl-3-methylimidazolium hydrogen sulfate ionic liquid can be reused.

[0027] In addition, due to the presence of a strong electron-donating dialkylamino group on each of the two benzyl rings, benzyl cleavage is likely to occur when the benzyl position of bis(4-(dialkylamino)phenyl)methane is oxidized under high temperature conditions, resulting in a reduced product yield. However, the oxidation reaction of the present invention is low, and the side reaction of benzyl cleavage is essentially absent, thereby further improving the selectivity and yield of the product. DETAILED DESCRIPTION

[0028] The present invention provides a method for preparing a Michler's ketone derivative, comprising the following steps:

[0029] Mixing bis(4-(dialkylamino)phenyl)methane, a catalyst, a 1-alkyl-3-methylimidazolium hydrogen sulfate ionic liquid, oxygen, and water to perform an oxidation reaction to obtain the Michler's ketone derivative;

[0030] The catalyst includes 2,3,5,6-tetrachlorobenzoquinone and tert-butyl nitrite;

[0031] The Michler's ketone derivatives include the structural formula shown in Formula I:

[0032] The R 1 and R 2 are independently C2-C18 alkyl groups.

[0033] In the present invention, the molar ratio of 2,3,5,6-tetrachlorobenzoquinone to tert-butyl nitrite is preferably 1:1-7, more preferably 1:2-6, and even more preferably 1:3-5.

[0034] In the present invention, the molar ratio of 2,3,5,6-tetrachlorobenzoquinone to bis(4-(dialkylamino)phenyl)methane is preferably 0.08 to 0.2:1, more preferably 0.1 to 0.16:1, and even more preferably 0.12 to 0.15:1.

[0035] In the present invention, the bis(4-(dialkylamino)phenyl)methane has the structural formula shown in Formula II:

[0036] The R 1 and R 2 are independently C2-C18 alkyl groups.

[0037] The bis(4-(dialkylamino)phenyl)methane preferably has the structural formulas shown in formulas (1-1) to (1-12):

[0038]

[0039] In the present invention, the mass ratio of the 1-alkyl-3-methylimidazolium hydrogen sulfate ionic liquid to bis(4-(dialkylamino)phenyl)methane is preferably 5 to 20:1, more preferably 8 to 15:1, and further preferably 10 to 12:1; the 1-alkyl-3-methylimidazolium hydrogen sulfate ionic liquid preferably includes one or more of 1-ethyl-3-methylimidazolium hydrogen sulfate, 1-butyl-3-methylimidazolium hydrogen sulfate, 1-propyl-3-methylimidazolium hydrogen sulfate and 1-hexyl-3-methylimidazolium hydrogen sulfate.

[0040] In the present invention, the molar ratio of water to bis(4-(dialkylamino)phenyl)methane is preferably 0.01 to 0.1:1, more preferably 0.04 to 0.08:1, and even more preferably 0.05 to 0.06:1. Water acts as an initiator of the oxidation reaction: During the reaction, a hydroxyl group is first formed at the benzylic position of the bis(4-(dialkylamino)phenyl)methane, which is then oxidized to a carbonyl group. Water initially provides the hydroxyl group and regenerates water later in the reaction.

[0041] In the present invention, the oxidation reaction is carried out in an environment filled with oxygen.

[0042] In the present invention, the mixing preferably comprises mixing bis(4-(dialkylamino)phenyl)methane, a catalyst, a 1-alkyl-3-methylimidazolium hydrogen sulfate ionic liquid, and water in a reactor, introducing oxygen into the reactor, and then sealing the reactor. To ensure sufficient oxygen within the reactor, the reactor outlet is preferably connected to a balloon filled with oxygen.

[0043] In the present invention, the temperature of the oxidation reaction is preferably 0-40°C, more preferably 10-30°C, further preferably 20-25°C, and the time is preferably 8-16 hours, more preferably 10-12 hours.

[0044] In the present invention, after the oxidation reaction, the process preferably further comprises extracting the product obtained by the oxidation reaction, removing the extractant and subjecting it to column treatment to obtain the Michler's ketone derivative.

[0045] In the present invention, the extractant for the extraction includes toluene.

[0046] The method of removing the extractant preferably comprises rotary evaporation.

[0047] The column treatment preferably includes: separating by column chromatography using a silica gel column, eluting with a mixture of ethyl acetate and petroleum ether in a volume ratio of 1:200, collecting the eluate and evaporating the solvent to obtain the Michler's ketone derivative.

[0048] In the present invention, the Michler's ketone derivative includes the structural formula shown in Formula I:

[0049] The R 1 and R 2 are independently C2-C18 alkyl groups.

[0050] The Michler's ketone derivative preferably has the structural formula shown in formula (2-1) to (2-12):

[0051]

[0052] The preparation method of the Michler's ketone derivative provided by the present invention is described in detail below with reference to the examples, but they should not be construed as limiting the scope of protection of the present invention.

[0053] Example 1

[0054] Preparation of bis(4-(diethylamino)phenyl)methanone (Formula (2-1))

[0055] In a 15 mL glass reaction tube, 1.5 g of the ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate, 0.4 mmol of bis(4-(diethylamino)phenyl)methane (Formula (1-1)), 0.04 mmol of 2,3,5,6-tetrachlorobenzoquinone, 0.12 mmol of tert-butyl nitrite, and 0.02 mmol of water were added and mixed thoroughly. Oxygen was introduced into the reaction tube, which was quickly sealed with a rubber stopper and pierced with an oxygen balloon. The reaction was allowed to react at 20°C for 12 h. The reaction system was extracted with toluene, and the resulting extract was rotary evaporated to remove the toluene. The extract was then separated by silica gel column chromatography and eluted with a mixture of ethyl acetate and petroleum ether (volume ratio: 1:200). The eluate was collected and the solvent was evaporated to obtain bis(4-(diethylamino)phenyl)methanone in a yield of 97%. The ionic liquid containing 2,3,5,6-tetrachlorobenzoquinone and water can be reused.

[0056] The hydrogen spectrum of bis(4-(diethylamino)phenyl)methanone was detected, and the results were as follows:

[0057] 1H NMR (500MHz, CDCl3) δ7.76 (d, J = 8.7Hz, 4H), 6.65 (d, J = 8.7Hz, 4H), 3.41 (q, J = 7.0Hz, 8H), 1.20 (t, J = 7.0Hz, 12H).

[0058] From the results of hydrogen spectrum, it can be seen that the product structure is formula (2-1).

[0059] Example 2

[0060] Preparation of bis(4-(diethylamino)phenyl)methanone (Formula (2-1))

[0061] The reaction steps were the same as in Example 1, except that the amount of tert-butyl nitrite was changed to 0.2 mmol. The isolated yield of bis(4-(diethylamino)phenyl)methanone was 98%.

[0062] Example 3

[0063] Preparation of bis(4-(diethylamino)phenyl)methanone (Formula (2-1))

[0064] The reaction steps were the same as in Example 1, except that the amount of 2,3,5,6-tetrachlorobenzoquinone was changed to 0.032 mmol, the reaction time was 16 h, and the isolated yield of bis(4-(diethylamino)phenyl)methanone was 92%.

[0065] Example 4

[0066] Preparation of bis(4-(diethylamino)phenyl)methanone (Formula (2-1))

[0067] The reaction steps were the same as in Example 1, except that the amount of 2,3,5,6-tetrachlorobenzoquinone was changed to 0.08 mmol, the reaction time was 8 h, and the isolated yield of bis(4-(diethylamino)phenyl)methanone was 96%.

[0068] Example 5

[0069] Preparation of bis(4-(di-n-propylamino)phenyl)methanone (Formula (2-2))

[0070] In a 15 mL glass reaction tube, 2.0 g of the ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate, 0.4 mmol of bis(4-(di-n-propylamino)phenyl)methane (Formula (1-1)), 0.04 mmol of 2,3,5,6-tetrachlorobenzoquinone, 0.12 mmol of tert-butyl nitrite, and 0.02 mmol of water were added and mixed thoroughly. Oxygen was introduced into the reaction tube, which was quickly sealed with a rubber stopper and pierced with an oxygen balloon. The reaction was allowed to react at 20°C for 12 h. The reaction system was extracted with toluene, and the resulting extract was rotary evaporated to remove the toluene. The extract was then separated by silica gel column chromatography and eluted with a mixture of ethyl acetate and petroleum ether in a volume ratio of 1:200. The eluate was collected and the solvent was evaporated to obtain bis(4-(di-n-propylamino)phenyl)methanone in a yield of 95%.

[0071] 1H NMR (500MHz, CDCl3) δ7.74 (d, J = 9.1Hz, 4H), 6.61 (d, J = 9.0Hz, 4H), 3.30 (t, J = 7.7Hz, 8H), 1.61-1.69 (m, 8H), 0.95 (t, J = 7.4Hz, 12H).

[0072] From the results of hydrogen spectrum, it can be seen that the product structure is formula (2-2).

[0073] Example 6

[0074] Preparation of bis(4-(di-n-butylamino)phenyl)methanone (Formula (2-3))

[0075] In a 15 mL glass reaction tube, 1.5 g of the ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate, 0.4 mmol of bis(4-(di-n-butylamino)phenyl)methane (Formula (1-3)), 0.06 mmol of 2,3,5,6-tetrachlorobenzoquinone, 0.12 mmol of tert-butyl nitrite, and 0.02 mmol of water were added and mixed thoroughly. Oxygen was introduced into the reaction tube, which was quickly sealed with a rubber stopper and pierced with an oxygen balloon. The reaction was allowed to react at 20°C for 10 h. The reaction system was extracted with toluene, and the resulting extract was rotary evaporated to remove the toluene. The extract was then separated by silica gel column chromatography and eluted with a mixture of ethyl acetate and petroleum ether in a volume ratio of 1:200. The eluate was collected and the solvent was evaporated to obtain bis(4-(di-n-butylamino)phenyl)methanone in a yield of 93%.

[0076] 1H NMR (500MHz, CDCl3) δ7.75 (d, J = 9.1Hz, 4H), 6.62 (d, J = 9.0Hz, 4H), 3.32 (t, J = 7.7Hz, 8H), 1.58-1.64 (m, 8H), 1.33-1.41 (m, 8H), 0.97 (t, J = 7.4Hz, 12H).

[0077] From the results of hydrogen spectrum, it can be seen that the product structure is formula (2-3).

[0078] Example 7

[0079] Preparation of bis(4-(di-n-pentylamino)phenyl)methanone (Formula (2-4))

[0080] In a 15 mL glass reaction tube, 1.5 g of the ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate, 0.4 mmol of bis(4-(di-n-pentylamino)phenyl)methane (Formula (1-4)), 0.04 mmol of 2,3,5,6-tetrachlorobenzoquinone, 0.12 mmol of tert-butyl nitrite, and 0.032 mmol of water were added and mixed thoroughly. Oxygen was introduced into the reaction tube, which was quickly sealed with a rubber stopper and pierced with an oxygen balloon. The reaction was allowed to react at 30°C for 11 h. The reaction system was extracted with toluene, and the resulting extract was rotary evaporated to remove the toluene. The extract was then separated by silica gel column chromatography and eluted with a mixture of ethyl acetate and petroleum ether in a volume ratio of 1:200. The eluate was collected and the solvent was evaporated to obtain bis(4-(di-n-pentylamino)phenyl)methanone in a yield of 96%.

[0081] The hydrogen spectrum of bis(4-(di-n-pentylamino)phenyl)methanone was detected, and the results were as follows:

[0082] 1H NMR(400MHz, CDCl3) δ7.76(d,J=8.5Hz,4H),6.62(d,J=8.6Hz,4H),3.33(t,J =7.8Hz,8H),1.60-1.64(m,8H),1.30-1.40(m,16H),0.93(t,J=6.9Hz,12H).

[0083] From the results of hydrogen spectrum, it can be seen that the product structure is formula (2-4).

[0084] Example 8

[0085] Preparation of bis(4-(di-n-hexylamino)phenyl)ketone (Formula (2-5))

[0086] In a 15 mL glass reaction tube, 1.5 g of the ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate, 0.4 mmol of bis(4-(di-n-hexylamino)phenyl)methane (Formula (1-5)), 0.04 mmol of 2,3,5,6-tetrachlorobenzoquinone, 0.12 mmol of tert-butyl nitrite, and 0.012 mmol of water were added and mixed thoroughly. Oxygen was introduced into the reaction tube, which was quickly sealed with a rubber stopper and pierced with an oxygen balloon. The reaction was allowed to react at 10°C for 15 h. The reaction system was extracted with toluene, and the resulting extract was rotary evaporated to remove the toluene. The extract was then separated by silica gel column chromatography and eluted with a mixture of ethyl acetate and petroleum ether in a volume ratio of 1:200. The eluate was collected and the solvent was evaporated to obtain bis(4-(di-n-hexylamino)phenyl)methanone in a yield of 95%.

[0087] The hydrogen spectrum of bis(4-(di-n-hexylamino)phenyl)methanone was detected, and the results were as follows:

[0088] 1H NMR (500MHz, CDCl3) δ7.77(d,J=8.9Hz,4H),6.61(d,J=8.9Hz,4H),3.32(t,J =7.7Hz,8H),1.59-1.66(m,8H),1.33-1.36(m,24H),0.91(t,J=6.8Hz,12H).

[0089] From the results of hydrogen spectrum, it can be seen that the product structure is formula (2-5).

[0090] Example 9

[0091] Preparation of bis(4-(di-n-octylamino)phenyl)ketone (Formula (2-6))

[0092] In a 15 mL glass reaction tube, 1.5 g of the ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate, 0.4 mmol of bis(4-(di-n-octylamino)phenyl)methane (Formula (1-6)), 0.04 mmol of 2,3,5,6-tetrachlorobenzoquinone, 0.12 mmol of tert-butyl nitrite, and 0.02 mmol of water were added and mixed thoroughly. Oxygen was introduced into the reaction tube, which was quickly sealed with a rubber stopper and pierced with an oxygen balloon. The reaction was allowed to react at 20°C for 12 h. The reaction system was extracted with toluene, and the resulting extract was rotary evaporated to remove the toluene. The extract was then separated by silica gel column chromatography and eluted with a mixture of ethyl acetate and petroleum ether in a volume ratio of 1:200. The eluate was collected and the solvent was evaporated to obtain bis(4-(di-n-octylamino)phenyl)methanone.

[0093] The hydrogen spectrum of bis(4-(di-n-octylamino)phenyl)methanone was detected, and the results were as follows:

[0094] 1H NMR (400MHz, CDCl3) δ7.75 (d, J = 8.9 Hz, 4H), 6.61 (d, J = 9.0 Hz, 4H), 3.32 (t, J = 7.6 Hz, 8H), 1.58-1.64 (m, 8H), 1.25-1.35 (m, 40H), 0.97-0.81 (m, 12H).

[0095] From the results of hydrogen spectrum, it can be seen that the product structure is formula (2-6).

[0096] Example 10

[0097] Preparation of bis(4-(n-octyl-n-dodecylamino)phenyl)methanone (Formula (2-7))

[0098] In a 15 mL glass reaction tube, 1.5 g of the ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate, 0.4 mmol of bis(4-(n-octyl-n-dodecylamino)phenyl)methane (Formula (1-7)), 0.04 mmol of 2,3,5,6-tetrachlorobenzoquinone, 0.12 mmol of tert-butyl nitrite, and 0.02 mmol of water were added and mixed thoroughly. Oxygen was introduced into the reaction tube, which was quickly sealed with a rubber stopper and pierced with an oxygen balloon. The reaction was allowed to react at 20°C for 12 h. The reaction system was extracted with toluene, and the resulting extract was rotary evaporated to remove the toluene. The extract was then separated by silica gel column chromatography and eluted with a mixture of ethyl acetate and petroleum ether in a volume ratio of 1:200. The eluate was collected and the solvent was evaporated to obtain bis(4-(n-octyl-n-dodecylamino)phenyl)methanone in a yield of 95%.

[0099] The hydrogen spectrum of bis(4-(n-octyl-n-dodecylamino)phenyl)methanone was detected, and the results were as follows:

[0100] 1H NMR (400MHz, CDCl3) δ7.74(d,J=8.8Hz,4H),6.61(d,J=8.9Hz,4H),3.30-3.34(m,8H),1.58-1.65(m 8H),1.26-1.35(m,56H),0.86-0.91(m,12H).

[0101] From the results of hydrogen spectrum, it can be seen that the product structure is formula (2-7).

[0102] Example 11

[0103] Preparation of bis(4-(n-octyl-n-tetradecylamino)phenyl)methanone (Formula (2-8))

[0104] In a 15 mL glass reaction tube, 1.5 g of the ionic liquid 1-ethyl-3-methylimidazole hydrogen sulfate, 0.4 mmol of bis(4-(n-octyl-n-tetradecylamino)phenyl)methane (Formula (1-8)), 0.04 mmol of 2,3,5,6-tetrachlorobenzoquinone, 0.12 mmol of tert-butyl nitrite, and 0.02 mmol of water were added and mixed thoroughly. Oxygen was introduced into the reaction tube, which was quickly sealed with a rubber stopper and pierced with an oxygen balloon. The reaction was allowed to react at 20°C for 12 h. The reaction system was extracted with toluene, and the resulting extract was rotary evaporated to remove the toluene. The extract was then separated by silica gel column chromatography and eluted with a mixture of ethyl acetate and petroleum ether in a volume ratio of 1:200. The eluate was collected and the solvent was evaporated to obtain bis(4-(n-octyl-n-tetradecylamino)phenyl)methanone in a yield of 93%.

[0105] The hydrogen spectrum of bis(4-(n-octyl-n-tetradecylamino)phenyl)methanone was detected, and the results were as follows:

[0106] 1H NMR (400MHz, CDCl3) δ7.75 (d, J = 8.9 Hz, 4H), 6.61 (d, J = 9.0 Hz, 4H), 3.30-3.34 (m, 8H), 1.57-1.65 (m, 8H), 1.27-1.33 (m, 64H), 0.87-0.91 (m, 12H).

[0107] From the results of hydrogen spectrum, it can be seen that the product structure is formula (2-8).

[0108] Example 12

[0109] Preparation of bis(4-(n-octyl-n-hexadecylamino)phenyl)methanone (Formula (2-9))

[0110] In a 15 mL glass reaction tube, 1.5 g of the ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate, 0.4 mmol of bis(4-(n-octyl-n-hexadecylamino)phenyl)methane (Formula (1-9)), 0.04 mmol of 2,3,5,6-tetrachlorobenzoquinone, 0.12 mmol of tert-butyl nitrite, and 0.02 mmol of water were added and mixed thoroughly. Oxygen was introduced into the reaction tube, which was quickly sealed with a rubber stopper and pierced with an oxygen balloon. The reaction was allowed to react at 20°C for 12 h. The reaction system was extracted with toluene, and the resulting extract was rotary evaporated to remove the toluene. The extract was then separated by silica gel column chromatography and eluted with a mixture of ethyl acetate and petroleum ether in a volume ratio of 1:200. The eluate was collected and the solvent was evaporated to obtain bis(4-(n-octyl-n-hexadecylamino)phenyl)methanone in a yield of 96%.

[0111] The hydrogen spectrum of bis(4-(n-octyl-n-hexadecylamino)phenyl)methanone was detected, and the results were as follows:

[0112] 1H NMR (400MHz, CDCl3) δ7.75 (d, J = 8.9 Hz, 4H), 6.61 (d, J = 9.0 Hz, 4H), 3.30-3.33 (m, 8H), 1.58-1.65 (m, 8H), 1.26-1.33 (m, 72H), 0.86-0.9 (m, 12H).

[0113] From the results of hydrogen spectrum, it can be seen that the product structure is formula (2-9).

[0114] Example 13

[0115] Preparation of bis(4-(n-octyl-n-octadecylamino)phenyl)methanone (Formula (2-10))

[0116] In a 15 mL glass reaction tube, 1.5 g of the ionic liquid 1-ethyl-3-methylimidazole hydrogen sulfate, 0.4 mmol of bis(4-(n-octyl-n-octadecylamino)phenyl)methane (Formula (1-10)), 0.04 mmol of 2,3,5,6-tetrachlorobenzoquinone, 0.12 mmol of tert-butyl nitrite, and 0.02 mmol of water were added and mixed thoroughly. Oxygen was introduced into the reaction tube, which was quickly sealed with a rubber stopper and pierced with an oxygen balloon. The reaction was allowed to react at 20°C for 12 h. The reaction system was extracted with toluene, and the resulting extract was rotary evaporated to remove the toluene. The extract was then separated by silica gel column chromatography and eluted with a mixture of ethyl acetate and petroleum ether in a volume ratio of 1:200. The eluate was collected and the solvent was evaporated to obtain bis(4-(n-octyl-n-octadecylamino)phenyl)methanone in a yield of 92%.

[0117] The hydrogen spectrum of bis(4-(n-octyl-n-octadecylamino)phenyl)methanone was detected, and the results were as follows:

[0118] 1H NMR (400MHz, CDCl3) δ7.74 (d, J = 8.9 Hz, 4H), 6.61 (d, J = 9.1 Hz, 4H), 3.30-3.34 (m, 8H), 1.58-1.65 (m, 8H), 1.26-1.35 (m, 80H), 0.87-0.91 (m, 12H).

[0119] From the results of hydrogen spectrum, it can be seen that the product structure is formula (2-10).

[0120] Example 14

[0121] Preparation of bis(4-(ethyl n-propylamino)phenyl)methanone (Formula (2-11))

[0122] In a 15 mL glass reaction tube, 1.5 g of the ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate, 0.4 mmol of bis(4-(ethyl-n-propylamino)phenyl)methane (Formula (1-11)), 0.04 mmol of 2,3,5,6-tetrachlorobenzoquinone, 0.12 mmol of tert-butyl nitrite, and 0.02 mmol of water were added and mixed thoroughly. Oxygen was introduced into the reaction tube, which was quickly sealed with a rubber stopper and pierced with an oxygen balloon. The reaction was allowed to react at 20°C for 12 h. The reaction system was extracted with toluene, and the resulting extract was rotary evaporated to remove the toluene. The extract was then separated by silica gel column chromatography and eluted with a mixture of ethyl acetate and petroleum ether in a volume ratio of 1:200. The eluate was collected and the solvent was evaporated to obtain bis(4-(ethyl-n-propylamino)phenyl)methanone in a yield of 92%.

[0123] The hydrogen spectrum of bis(4-(ethyl-n-propylamino)phenyl)methanone was detected, and the results were as follows:

[0124] 1H NMR (400MHz, CDCl3) δ7.75 (d, J = 9.0Hz, 4H), 6.63 (d, J = 9.0Hz, 4H), 3.43 (q, J = 7.1Hz, 4H) ,3.29(t,J=7.7Hz,4H),1.61-1.70(m,4H),1.19(t,J=7.0Hz,6H),0.96(t,J=7.4Hz,6H).

[0125] From the results of hydrogen spectrum, it can be seen that the product structure is formula (2-11).

[0126] Example 15

[0127] Preparation of bis(4-(ethyl n-butylamino)phenyl)methanone (Formula (2-12))

[0128] In a 15 mL glass reaction tube, 1.5 g of the ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate, 0.4 mmol of bis(4-(ethyl-n-butylamino)phenyl)methane (Formula (1-12)), 0.04 mmol of 2,3,5,6-tetrachlorobenzoquinone, 0.12 mmol of tert-butyl nitrite, and 0.02 mmol of water were added and mixed thoroughly. Oxygen was introduced into the reaction tube, which was quickly sealed with a rubber stopper and pierced with an oxygen balloon. The reaction was allowed to react at 20°C for 12 h. The reaction system was extracted with toluene, and the resulting extract was rotary evaporated to remove the toluene. The extract was then separated by silica gel column chromatography and eluted with a mixture of ethyl acetate and petroleum ether in a volume ratio of 1:200. The eluate was collected and the solvent was evaporated to obtain bis(4-(ethyl-n-butylamino)phenyl)methanone in a yield of 94%.

[0129] The hydrogen spectrum of bis(4-(ethyl-n-butylamino)phenyl)methanone was detected, and the results were as follows:

[0130] 1H NMR (400MHz, CDCl3) δ7.76(d,J=9.0Hz,4H),6.64(d,J=9.0Hz,4H),3.43(q,J=7.1Hz,4H),3.32(t, J=7.6Hz,4H),1.58-1.65(m,4H),1.33-1.43(m,4H),1.20(t,J=7.0Hz,6H),0.97(t,J=7.4Hz,6H).

[0131] From the results of hydrogen spectrum, it can be seen that the product structure is formula (2-12).

[0132] Example 16

[0133] The ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate, dissolved in 2,3,5,6-tetrachlorobenzoquinone and water, prepared in Example 1, was repeatedly used in the catalytic oxidation of bis(4-(diethylamino)phenyl)methane to produce bis(4-(diethylamino)phenyl)methanone. The method of use was the same as in Example 1, except that no fresh 2,3,5,6-tetrachlorobenzoquinone or water was added. The solution was recycled three times, and the reaction results are shown in Table 1.

[0134] Table 1 Performance of recycled ionic liquids

[0135]

[0136] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a Michler's ketone derivative, characterized in that: The steps are: Mixing bis(4-(dialkylamino)phenyl)methane, a catalyst, a 1-alkyl-3-methylimidazolium hydrogen sulfate ionic liquid, oxygen, and water to perform an oxidation reaction to obtain the Michler's ketone derivative; The catalyst is 2,3,5,6-tetrachlorobenzoquinone and tert-butyl nitrite; The molar ratio of 2,3,5,6-tetrachlorobenzoquinone to tert-butyl nitrite is 1:1-7; The 1-alkyl-3-methylimidazolium hydrogen sulfate ionic liquid is one or more of 1-ethyl-3-methylimidazolium hydrogen sulfate, 1-butyl-3-methylimidazolium hydrogen sulfate, 1-propyl-3-methylimidazolium hydrogen sulfate and 1-hexyl-3-methylimidazolium hydrogen sulfate; The molar ratio of water to bis(4-(dialkylamino)phenyl)methane is 0.01 to 0.1:1 The Michler's ketone derivatives include the structural formula shown in Formula I: Formula I; said R 1 and R 2 are independently C2~C18 alkyl; The temperature of the oxidation reaction is 0-40°C.

2. The preparation method according to claim 1, characterized in that The bis(4-(dialkylamino)phenyl)methane has the structural formula shown in Formula II: Formula II.

3. The preparation method according to claim 1 or 2, characterized in that The molar ratio of the 2,3,5,6-tetrachlorobenzoquinone to bis(4-(dialkylamino)phenyl)methane is 0.08-0.20:

1.

4. The preparation method according to claim 1 or 2, characterized in that The mass ratio of the 1-alkyl-3-methylimidazolium hydrogen sulfate ionic liquid to bis(4-(dialkylamino)phenyl)methane is 5-20:

1.

5. The preparation method according to claim 1, characterized in that The oxidation reaction time is 8 to 16 hours.

6. The preparation method according to claim 1, characterized in that After the oxidation reaction, the method further comprises extracting the product obtained by the oxidation reaction, removing the extractant and performing column treatment to obtain the pure product of the Michler's ketone derivative.

7. The preparation method according to claim 6, characterized in that The extraction agent of the extraction is toluene.

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