Diimine cobalt complexes, methods for their preparation and use

Abstract

The application belongs to the field of catalytic synthesis chemistry, and particularly relates to a diimine type cobalt complex and a preparation method and application thereof. An active center metal cobalt of the diimine type cobalt complex is a transition metal with rich mineral resources, low cost and low toxicity, and has high reaction activity. When the diimine type cobalt complex is used for catalyzing reduction of ketones and imines, the diimine type cobalt complex has wide universality for substrates, and has mild conditions, low dosage and high yield, and thus provides a possibility for industrial application.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalytic synthesis chemistry, and particularly relates to a diimine type cobalt complex and a preparation method and application thereof. BACKGROUND

[0002] Alcohols and amines are widely present in nature, such as optically active alcohols, proteins, nucleic acids and alkaloids, and have important application value and industrial significance in the synthesis of natural products and chiral drugs, pesticides, fine chemicals and biomaterials. Therefore, it is particularly important to study and master the synthesis method of alcohols and amines. Important progress has been made in the catalytic hydrogenation of ketones and imines using late transition metals. The synthesis method using noble metals such as ruthenium, rhodium, iridium, platinum and palladium as catalysts and hydrogen as reducing agent occupies a dominant position, but the high cost and high toxicity of these catalysts limit their further application.

[0003] Cobalt is a crust-abundant element, and has been widely concerned due to its low cost and good biological compatibility. However, the current cobalt catalysts are mainly based on phosphine ligands, and the synthesis steps are complicated and the cost is high, which limits its application. Therefore, it is of great significance to develop a cobalt complex with low toxicity and easy synthesis for catalytic reduction of alcohols and amines. SUMMARY

[0004] The purpose of the present application is to provide a diimine type cobalt complex, and to catalyze the reduction of ketones or imines to obtain alcohols and amines.

[0005] Another purpose of the present application is to provide a preparation method of the diimine type cobalt complex.

[0006] Another purpose of the present application is to provide the application of the diimine type cobalt complex in catalyzing the reduction of ketones or imines.

[0007] To achieve the above purpose, the present application realizes the following technical solutions:

[0008] The diimine cobalt complex has the structure of formula (I) or formula (II):

[0009]

[0010]

[0011] The R is one of tert-butyl, The R is one of tert-butyl,

[0012] Further, the R is tert-butyl.

[0013] The preparation method of the diimine cobalt complex comprises the following steps:

[0014] The cobalt dichloride and the diimine type ligand are stirred and reacted in a solvent under an inert atmosphere, and a first post-treatment is performed to obtain the diimine cobalt complex. one of the following.

[0015] Specifically, the synthesis route is as follows:

[0016]

[0017] Further, the diimine type ligand is

[0018] Further, the diimine type ligand is

[0019] Further, the molar ratio of the cobalt dichloride and the diimine type ligand is 1.05-1:1.

[0020] Further, the solvent is tetrahydrofuran.

[0021] Further, the reaction time is 12-24 hours.

[0022] Further, the first post-treatment is to remove the solvent, then wash with n-hexane, filter, and remove the residual n-hexane to obtain the diimine cobalt complex.

[0023] The application also protects the use of the diimine cobalt complex in catalytic reduction of ketones or imines.

[0024] A method for catalytic reduction of ketones or imines, comprising the following steps:

[0025] A ketone or imine compound is dissolved as a substrate in a solvent, and the above diimine cobalt complex is used as a catalyst to perform a catalytic reduction reaction at room temperature in the presence of a hydrogen source, and a second post-treatment is performed to obtain an alcohol or amine compound.

[0026] Further, the hydrogen source is ammonia borane.

[0027] Further, the molar ratio of the substrate, hydrogen source and diimine cobalt complex is 1:1.5-2:0.01-0.05.

[0028] Further, the ketone compound has the structure of formula (III):

[0029]

[0030] R 1 and R 2independently selected from benzene ring, monosubstituted benzene ring, naphthalene ring, pyridine ring, indane, one of alkyl with carbon number of 3-6; the monosubstituted methyl, methoxy, amine group, nitro, fluorine, chlorine, bromine, iodine, cyano;

[0031] The imine compound has the structure of formula (IV):

[0032]

[0033] R 3 selected from hydrogen, methyl, methoxy, hydroxyl, amine group, nitro fluorine, chlorine, bromine or cyano; the R 4 selected from phenyl, 4-methylphenyl, 4-methoxyphenyl, 4-hydroxyphenyl, 4-chlorophenyl, tert-butyl.

[0034] Further, the solvent is one of isopropyl alcohol, methanol, tetrahydrofuran, toluene, dichloromethane or acetonitrile.

[0035] Still further, the solvent is one of isopropyl alcohol, methanol or tetrahydrofuran.

[0036] Still further, the solvent is isopropyl alcohol.

[0037] Further, the second post-treatment is to use ethyl acetate to extract, add column chromatography silica gel, remove the solvent by rotary evaporation, separate by column chromatography, use petroleum ether and ethyl acetate with a volume ratio of 10:1 as eluent, and remove the solvent under reduced pressure to obtain the product.

[0038] Compared with the prior art, the present application has the following beneficial effects:

[0039] The present application provides a diimine type cobalt complex and a preparation method and application thereof. The active center metal cobalt of the diimine type cobalt complex is a transition metal with abundant mineral resources, is cheap and low-toxic, and has high reaction activity. When the diimine cobalt complex is used as a catalyst to catalyze the reduction of ketone and imine, the conditions are mild, the catalyst consumption is low, the yield is high, and the substrate universality is wide, which provides the possibility for industrial application. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 It is the nuclear magnetic hydrogen spectrum of the product of catalytic reduction of acetophenone in Example 5;

[0041] Figure 2 It is the nuclear magnetic hydrogen spectrum of the product of catalytic reduction of 3-acetylpyridine in Example 6;

[0042] Figure 3 It is the nuclear magnetic hydrogen spectrum of the product of catalytic reduction of acetonaphthone in Example 7;

[0043] Figure 4The hydrogen nuclear magnetic resonance spectrum of the product of catalytic reduction of benzophenone in Example 8;

[0044] Figure 5 The hydrogen nuclear magnetic resonance spectrum of the product of catalytic reduction of 2-indanone in Example 9;

[0045] Figure 6 The hydrogen nuclear magnetic resonance spectrum of the product of catalytic reduction of N-p-cyanobenzylideneaniline in Example 10;

[0046] Figure 7 The hydrogen nuclear magnetic resonance spectrum of the product of catalytic reduction of N-p-nitrobenzylidene-t-butylamine in Example 11;

[0047] Figure 8 The hydrogen nuclear magnetic resonance spectrum of the product of catalytic reduction of benzylidene-p-methoxyaniline in Example 12;

[0048] Figure 9 The hydrogen nuclear magnetic resonance spectrum of the product of catalytic reduction of N-cyanobenzylidene-p-methoxyaniline in Example 13. DETAILED DESCRIPTION

[0049] The present application will be further described in conjunction with specific examples, which are intended to explain the present application, but not to limit the scope of the present application. The test methods used in the following examples are conventional methods unless otherwise specified; the materials, reagents, etc. used are commercially available reagents and materials unless otherwise specified.

[0050] Example 1

[0051] A method for preparing a diimine type cobalt complex includes the following steps:

[0052] A diimine type ligand (1 mmol) was weighed and dissolved in 5 mL of tetrahydrofuran, and cobalt dichloride (143 mg, 1.1 mmol) was weighed and dissolved in 5 mL of tetrahydrofuran to form a suspension, which was then added dropwise to the tetrahydrofuran solution of the diimine type ligand. The reaction was carried out at room temperature for 12 hours. The solvent was removed under reduced pressure, and the solid was washed with n-hexane and filtered to obtain the diimine type cobalt complex with a yield of 97%. Elemental analysis, C 10 H 20 Cl2CoN2Calculated: C 40.29; H 6.76; N 9.40, Found: C 40.18; H 6.66; N 9.28; the diimine type ligand is as follows:

[0053]

[0054] Example 2

[0055] A method for preparing a diimine type cobalt complex includes the following steps:

[0056] The procedure and parameters were the same as in Example 1, except that the diimine type ligand was as follows:

[0057]

[0058] Yield 91%. Elemental analysis, C 20 H 24 Cl2CoN2Calculated: C 56.89; H 5.73; N 6.63, Found: C 56.78; H 5.67; N 6.48.

[0059] Example 3

[0060] A method for preparing a diimine type cobalt complex, comprising the following steps:

[0061] The procedure and parameters were the same as in Example 1, except that the diimine type ligand was as follows:

[0062]

[0063] Yield 91%. Elemental analysis, C 26 H 36 Cl2CoN2Calculated: C 61.66; H 7.17; N 5.53, Found: C 61.57; H 7.03; N 5.47.

[0064] Example 4

[0065] A method for preparing a diimine type cobalt complex, comprising the following steps:

[0066] The procedure and parameters were the same as in Example 1, except that the diimine type ligand was as follows:

[0067]

[0068] Yield 92%. Elemental analysis, C 10 H8Cl2CoN2Calculated: C 41.99; H 2.82; N 9.79, Found: C 41.87; H 2.75; N 9.68.

[0069] Example 5

[0070] This example provides a method for catalytic reduction of acetophenone by the diimine type cobalt complex described in Example 1, comprising the following steps:

[0071]

[0072] Take acetophenone (120 mg, 1.0 mmol), ammonia borane (46.3 mg, 1.5 mmol) and the diimine type cobalt complex prepared in Example 1 (2.97 mg, 0.01 mmol) respectively in a round bottom flask, add 2 mL of isopropyl alcohol, stir the reaction at room temperature for 30 minutes in a closed system. Monitor the reaction by TLC, after the reaction is completed, use ethyl acetate for extraction, add column chromatography silica gel, rotary evaporation to remove the solvent, and column chromatography to separate the target product. The eluent is petroleum ether and ethyl acetate in a volume ratio of 10:1, and finally the target product is obtained with a yield of 99%. The nuclear magnetic hydrogen spectrum data are as follows: 1 H NMR (400 MHz, Chloroform-d) δ 7.35-7.23 (m, 5H), 4.86-4.80 (m, 1H), 1.45 (d, J = 6.5 Hz, 3H).

[0073] Example 6

[0074] This example provides a method for catalytic reduction of 3-acetylpyridine by the diimine type cobalt complex described in Example 1, comprising the following steps:

[0075]

[0076] Take 3-acetylpyridine (121.0 mg, 1.0 mmol), ammonia borane (46.3 mg, 1.5 mmol) and the diimine type cobalt complex prepared in Example 1 (2.97 mg, 0.01 mmol) respectively in a round bottom flask, add 2 mL of isopropyl alcohol, stir the reaction at room temperature for 30 minutes in a closed system. Monitor the reaction by TLC, after the reaction is completed, use ethyl acetate for extraction, add column chromatography silica gel, rotary evaporation to remove the solvent, and column chromatography to separate the target product. The eluent is petroleum ether and ethyl acetate in a volume ratio of 5:1, and finally the target product is obtained with a yield of 98%. The nuclear magnetic hydrogen spectrum data are as follows: 1 H NMR (400 MHz, Chloroform-d) δ 8.40 (d, J = 2.1 Hz, 1H), 8.29 (dd, J = 4.9, 1.7 Hz, 1H), 7.74 (dt, J = 7.8, 2.0 Hz, 1H), 7.22 (dd, J = 7.9, 4.0 Hz, 1H), 5.90 (s, 1H), 4.88 (q, J = 6.5 Hz, 1H), 1.47 (d, J = 6.5 Hz, 3H).

[0077] Example 7

[0078] This example provides a method for catalytic reduction of acetophenone by the diimine type cobalt complex described in Example 1, comprising the following steps:

[0079]

[0080] Naphthaleneacetone (170 mg, 1.0 mmol), ammonia borane (46.3 mg, 1.5 mmol) and diimine type cobalt complex prepared in example 1 (2.97 mg, 0.01 mmol) were weighed separately in a round bottom flask, 2 mL of isopropyl alcohol was added and stirred at room temperature for 10 minutes in a closed system. The reaction was monitored by TLC, after completion of the reaction, extraction was done using ethyl acetate, column chromatography silica gel was added, solvent was removed by rotary evaporation, column chromatography was used to separate the target product. Eluent was petroleum ether and ethyl acetate in the ratio of 10:1 by volume, finally the target product was obtained with 94% yield. The proton NMR data is as follows: 1 H NMR (400 MHz, Chloroform-d): δ 7.79 - 7.72 (m, 4H), 7.47 - 7.39 (m, 3H), 4.96 (q, J = 6.5 Hz, 1H), 2.34 (s, 1H), 1.51 (d, J = 6.5 Hz, 3H).

[0081] Example 8

[0082] This example provides for the catalytic reduction of benzophenone by diimine type cobalt complex as described in example 1, comprising the following steps:

[0083]

[0084] Benzophenone (182 mg, 1.0 mmol), ammonia borane (46.3 mg, 1.5 mmol) and diimine type cobalt complex prepared in example 1 (2.97 mg, 0.01 mmol) were weighed separately in a round bottom flask, 2 mL of isopropyl alcohol was added and stirred at room temperature for 30 minutes in a closed system. The reaction was monitored by TLC, after completion of the reaction, extraction was done using ethyl acetate, column chromatography silica gel was added, solvent was removed by rotary evaporation, column chromatography was used to separate the target product. Eluent was petroleum ether and ethyl acetate in the ratio of 10:1 by volume, finally the target product was obtained with 96% yield. The proton NMR data is as follows: 1 H NMR (400 MHz, Chloroform-d) δ 7.34 - 7.27 (m, 8H), 7.25 - 7.20 (m, 2H), 5.74 (s, 1H), 2.42 (s, 1H).

[0085] Example 9

[0086] This example provides for the catalytic reduction of 2-indanone by diimine type cobalt complex as described in example 1, comprising the following steps:

[0087]

[0088] Take 2-indanone (132 mg, 1.0 mmol), ammonia borane (46.3 mg, 1.5 mmol) and the diimine cobalt complex prepared in Example 1 (2.97 mg, 0.01 mmol) separately into a round bottom flask, add 2 mL of isopropyl alcohol, stir the reaction at room temperature for 30 minutes in a closed system. Monitor the reaction by TLC, after the reaction is completed, use ethyl acetate for extraction, add column chromatography silica gel, remove the solvent by rotary evaporation, separate the target product by column chromatography. The eluent is petroleum ether and ethyl acetate in a volume ratio of 10:1, and finally the target product is obtained with a yield of 95%. The nuclear magnetic hydrogen spectrum data are as follows: 1 H NMR (400 MHz, Chloroform-d) δ 7.65-7.63 (m, 2H), 7.50-7.47 (m, 2H), 4.97 (q, J = 6.5 Hz, 1H), 2.07-2.02 (m, 2H), 1.50 (d, J = 6.5 Hz, 2H).

[0089] Example 10

[0090] This example provides a method for catalytic reduction of N-p-cyanobenzylidene aniline by the diimine cobalt complex described in Example 1, which comprises the following steps:

[0091]

[0092] Take N-p-cyanobenzylidene aniline (206.1 mg, 1.0 mmol), ammonia borane (46.3 mg, 1.5 mmol) and the diimine cobalt complex prepared in Example 1 (2.97 mg, 0.01 mmol) separately into a round bottom flask, add 2 mL of isopropyl alcohol, stir the reaction at room temperature for 2 hours in a closed system. Monitor the reaction by TLC, after the reaction is completed, use ethyl acetate for extraction, add column chromatography silica gel, remove the solvent by rotary evaporation, separate the target product by column chromatography. The eluent is petroleum ether and ethyl acetate in a volume ratio of 10:1, and finally the target product is obtained with a yield of 93%. The nuclear magnetic hydrogen spectrum data are as follows: 1 H NMR (400 MHz, Chloroform-d) δ 7.63-7.61 (m, 2H), 7.49-7.47 (m, 2H), 7.19-7.15 (m, 2H), 6.76-6.72 (m, 1H), 6.59-6.56 (m, 2H), 4.43 (d, J = 5.7 Hz, 2H), 4.20 (br, 1H).

[0093] Example 11

[0094] This example provides a method for catalytic reduction of N-p-nitrosobenzylidene tert-butylamine by the diimine cobalt complex described in Example 1, which comprises the following steps:

[0095]

[0096] Substituted N-p-nitrobenzylidene tert-butylamine (206 mg, 1.0 mmol), ammonia borane (46.3 mg, 1.5 mmol) and diimine type cobalt complex prepared in example 1 (2.97 mg, 0.01 mmol) were weighed separately in a round bottom flask, 2 mL of isopropyl alcohol was added and stirred at room temperature for 2 hours in a closed system. The reaction was monitored by TLC, after completion of the reaction, extraction was done using ethyl acetate, column chromatography silica gel was added, solvent was removed by rotary evaporation, column chromatography was used to separate the target product. Eluent was petroleum ether and ethyl acetate in the ratio of 10:1 by volume, finally the target product was obtained with 94% yield. The proton NMR data is as follows: 1 HNMR (400 MHz, Chloroform-d) δ 8.18 - 8.15 (m, 2H), 7.55 - 7.52 (m, 2H), 3.84 (s, 2H), 1.18 (s, 9H).

[0097] Example 12

[0098] This example provides for the catalytic reduction of N-cyanobenzylidene p- methoxy aniline by diimine type cobalt complex as described in example 1, comprising the following steps:

[0099]

[0100] Substituted N-p-nitrobenzylidene tert-butylamine (206 mg, 1.0 mmol), ammonia borane (46.3 mg, 1.5 mmol) and diimine type cobalt complex prepared in example 1 (2.97 mg, 0.01 mmol) were weighed separately in a round bottom flask, 2 mL of isopropyl alcohol was added and stirred at room temperature for 2 hours in a closed system. The reaction was monitored by TLC, after completion of the reaction, extraction was done using ethyl acetate, column chromatography silica gel was added, solvent was removed by rotary evaporation, column chromatography was used to separate the target product. Eluent was petroleum ether and ethyl acetate in the ratio of 10:1 by volume, finally the target product was obtained with 94% yield. The proton NMR data is as follows: 1 HNMR (400 MHz, Chloroform-d) δ 8.18 - 8.15 (m, 2H), 7.55 - 7.52 (m, 2H), 3.84 (s, 2H), 1.18 (s, 9H).

[0101] Example 13

[0102] This example provides for the catalytic reduction of N-cyanobenzylidene p- methoxy aniline by diimine type cobalt complex as described in example 1, comprising the following steps:

[0103]

[0104] N-cyanobenzylic benzylidene p-methoxyaniline (236 mg, 1.0 mmol), borane amine (46.3 mg, 1.5 mmol) and diimine cobalt complex prepared in example 1 (2.97 mg, 0.01 mmol) were taken in a round bottom flask, 2 mL of isopropyl alcohol was added and stirred at room temperature for 2 h in a closed system. The reaction was monitored by TLC and after completion of the reaction, extracted using ethyl acetate and column chromatography was performed using silica gel. The column was eluted with petroleum ether and ethyl acetate in the ratio of 10:1 and the target product was obtained in 88% yield. The proton NMR data is as follows: 1 HNMR (400 MHz, Chloroform-d) δ 7.62 - 7.59 (m, 2H), 7.48 - 7.46 (m, 2H), 6.80 - 6.72 (m, 2H), 6.57 - 6.49 (m, 2H), 4.37 (s, 2H), 3.96 (br, 1H), 3.72 (s, 3H).

[0105] Examples 14-17

[0106] Diimine cobalt complexes prepared in examples 1-4 were used to catalyze the reduction of acetophenone as per the procedure described in example 5, where borane amine was taken in 2 mmol and each diimine cobalt complex was taken in 0.02 mmol, and the target product was obtained in 99%, 70%, 65% and 43% yield respectively.

[0107] Examples 18-22

[0108] Diimine cobalt complex prepared in example 1 was used to catalyze the reduction of acetophenone as per the procedure described in example 5, where borane amine was taken in 2 mmol and diimine cobalt complex was taken in 0.02 mmol, and the target product was obtained in 80%, 67%, 42%, 42% and 31% yield respectively using methanol, tetrahydrofuran, acetonitrile, toluene and dichloromethane as solvents.

[0109] Example 23

[0110] Diimine cobalt complex prepared in example 1 was used to catalyze the reduction of acetophenone as per the procedure described in example 5, where borane amine was taken in 1 mmol and diimine cobalt complex was taken in 0.02 mmol, and the target product was obtained in 50% yield.

[0111] Obviously, the above embodiments of the present application are merely exemplary but not intended to limit the embodiments of the present application. Based on the above description, any other variations or changes can be made by those skilled in the art without departing from the spirit and principles of the present application. It is not necessary to list all the embodiments here. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall fall within the scope of the claims of the present application.

Claims

1. A method of catalytic reduction of a ketone or imine, characterized in that, The method comprises the following steps: The ketone compound or imine compound is dissolved as a substrate in a solvent, a cobalt diimine complex is used as a catalyst, a hydrogen source is present, and catalytic reduction is carried out at room temperature, and then a second post-treatment is performed to obtain an alcohol or amine compound; the hydrogen source is ammonia borane; The solvent is one or more of isopropyl alcohol, methanol, tetrahydrofuran, toluene, dichloromethane or acetonitrile; The cobalt diimine complex has a structure of formula (I) or formula (II): Formula (I); Formula (II); R is one of the group consisting of or one of the group consisting of The ketone compound has a structure of formula (III): （Ⅲ）； R 1 and R 2 is independently selected from one of a benzene ring, a benzene ring substituted with one substituent, a naphthalene ring, a pyridine ring, an indane, or an alkyl group having a carbon number of 3 to 6; the substituent is one of a methyl group, a methoxy group, a nitro group, fluorine, chlorine, bromine, iodine, or a cyano group; The imine compound has a structure of formula (IV): （Ⅳ）； R 3 one selected from hydrogen, methyl, methoxy, hydroxy, nitro, fluorine, chlorine, bromine or cyano; R 4 one selected from phenyl, 4-methylphenyl, 4-methoxyphenyl, 4-hydroxyphenyl, 4-chlorophenyl, t-butyl.

2. The method of claim 1, wherein, The R is a tert-butyl group.

3. The method of claim 1, wherein, The preparation method of the cobalt diimine complex is as follows: under an inert atmosphere, cobalt dichloride and a diimine type ligand are stirred and reacted in a solvent, and then a first post-treatment is performed to obtain the cobalt diimine complex. The diimine type ligand is one of , , or .

4. The method of claim 3, wherein, The molar ratio of the cobalt dichloride to the diimine type ligand is 1.05-1:

1.

5. The method of claim 3, wherein, The reaction time is 12-24 hours.

6. The method of claim 3, wherein, The first post-treatment is as follows: after the solvent is removed, washing is performed using n-hexane, filtration is performed, and residual n-hexane is removed to obtain the cobalt diimine complex.

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