WO2019200522A1

WO2019200522A1 - Application of o-methylanilino lithium in catalyzing hydroboration of carbonyl compound and borane

Info

Publication number: WO2019200522A1
Application number: PCT/CN2018/083250
Authority: WO
Inventors: 薛明强; 朱章野; 武振杰; 洪玉标; 蔡玲霞; 沈琪
Original assignee: 南通纺织丝绸产业技术研究院; 苏州大学
Priority date: 2018-04-17
Filing date: 2018-04-17
Publication date: 2019-10-24

Abstract

Disclosed is an application of o-methylanilino lithium in catalyzing hydroboration of a carbonyl compound and borane. In an anhydrous oxygen-free environment, borane is added in an inert gas atmosphere to a reaction flask having been subjected to dehydration and deoxidation treatment, then a catalyst o-methylanilino lithium is added and uniformly mixed, a carbonyl compound is further added to carry out hydroboration, and the reaction is terminated by exposure to air to obtain a borate. The present invention has found for the first time that o-methylanilino lithium can be extremely efficient in catalyzing the hydroboration of carbonyl compounds, and thus provides a novel solution for the preparation of borates by hydroboration of carbonyl compounds with borane. The o-methylanilino lithium has high catalytic activity in the hydroboration of the carbonyl compound and borane with mild reaction conditions, a short reaction time, and a high reaction yield. The reaction is simple and controllable, involves simple post-treatment, and employs a solvent-free system, thereby reducing environmental pollution. The disclosed catalyst is widely applicable to aromatic aldehydes (ketones) having different substitution positions and different electronic effects and to heterocyclic aldehydes (ketones) and fatty aldehydes (ketones), thereby providing more choices for obtaining borate compounds with different substituent structures.

Description

Application of o-methylanilinium lithium in catalytic carbonyl compound and borane hydroboration

Technical field

The invention relates to the application of o-methylanilinyl lithium, in particular to the high-efficiency application of o-methylanilinyl lithium in catalyzing the borohydride hydroboration reaction of a carbonyl compound.

Background technique

The product of the hydroboration reaction, borate ester compound, can be used not only as a polymer additive, a gasoline additive, a flame retardant or a sterilizing agent, but also as a special surfactant, a lubricating oil additive and an automobile brake fluid, etc. Very extensive. For the hydroboration of equivalent catalytic carbonyl compounds, the hydrolysis of the obtained boronic ester products is also a very effective method for synthesizing alcohols in contemporary organic synthetic chemistry. Therefore, the research on the hydroboration reaction of unsaturated bonds is of great significance to modern industrial and organic synthetic chemistry, which has attracted wide attention of researchers.

A wide variety of catalysts have been used for the hydroboration of carbonyl compounds, especially in recent years, and there have been many reports on such reactions. The hydroboration reaction of the carbonyl compound is difficult to occur due to the absence of a catalyst. So the focus of research on this type of reaction is to develop efficient catalytic systems. However, the catalyst systems reported so far are relatively expensive or the reaction conditions are relatively harsh.

Therefore, it is particularly urgent to develop a catalytic system for efficiently catalyzing the hydroboration of aldehydes under mild conditions.

technical problem

The object of the present invention is to provide the use of o-methylanilinyl lithium, which is characterized in that the o-methylanilinyl lithium is used as a high-efficiency catalyst to catalyze the borohydride reaction of a carbonyl compound with a borane; :2-Me-PhNHLi, its chemical structure is as follows:

.

Technical solution

In order to achieve the above object, the technical solution adopted by the present invention is: the application of o-methylanilinyl lithium in catalyzing the borohydride hydroboration reaction of a carbonyl compound.

The invention also discloses a method for the above hydroboration reaction, comprising the following steps:

In an anhydrous and oxygen-free environment, under a noble gas atmosphere, borane is added to the reaction bottle subjected to dehydration and deoxidation treatment, then the catalyst o-methylanilinyl lithium is added, uniformly mixed, and then a carbonyl compound is added to cause a hydroboration reaction.

The invention further discloses a method for preparing a boric acid ester, comprising the following steps:

In an anhydrous oxygen-free environment, in an inert gas atmosphere, borane is added to the reaction bottle subjected to dehydration and deoxidation treatment, then the catalyst o-methylanilinyl lithium is added, uniformly mixed, and then a carbonyl compound is added to cause a hydroboration reaction, and the exposure is carried out. The reaction was terminated in air to obtain a boric acid ester.

In the above technical solution, the carbonyl compound is selected from the group consisting of an aromatic aldehyde, a heterocyclic aldehyde, a fatty aldehyde, an aromatic ketone, a heterocyclic ketone or a fatty ketone;

The chemical structure of the aromatic aldehyde is as follows:

The chemical structure of the aromatic ketone is as follows:

Wherein R, R' independently selected from the group consisting of an electron withdrawing group or an electron donating group, may be selected from the group consisting of halogen, methyl, methoxy;

The heterocyclic aldehyde is selected from the group consisting of 2 pyridine formaldehyde or 2- thiophene formaldehyde;

The fatty aldehyde is selected from the group consisting of cyclohexylformaldehyde, propionaldehyde, and n-heptanal;

The heterocyclic ketone is selected from 2-acetylthiophene;

The fatty ketone is selected from the group consisting of methyl isopropyl ketone and 4-heptanone;

The borane is selected from the group consisting of pinacol borane;

The catalyst is used in an amount of 0.1-0.4% by mole of the carbonyl compound, and the molar ratio of the carbonyl compound to the borane is 1:1.1;

The temperature of the hydroboration reaction is room temperature for a period of 10 to 40 minutes, preferably 10 minutes.

The above technical solutions can be expressed as follows:

R ¹ and R ^{2 are} derived from the starting carbonyl compound.

Beneficial effect

Due to the application of the above technical solutions, the present invention has the following advantages compared with the prior art:

1. The present invention finds for the first time that o-methylanilinyl lithium can extremely efficiently catalyze the borohydride reaction of aldehyde/ketone with borane, and provides a new scheme for preparing boric acid ester by hydroboration of carbonyl compound with borane.

2. The ortho-methylanilinyl lithium disclosed in the present invention has high catalytic activity for borohydride hydrogenation reaction with borane (catalyst dosage is only 0.1%), mild reaction conditions (room temperature), short reaction time (10 min), and The reaction yield is high, the reaction is simple and controllable, the post-treatment is simple, and the reaction adopts a solvent-free system, which reduces environmental pollution.

3. The catalyst disclosed in the invention has good universality for aromatic aldehydes (ketones) with different substitution positions and different electronic effects, and for heterocyclic aldehydes (ketones) and fatty aldehydes (ketones), in order to obtain different substituent structures. Borate compounds offer more options.

Embodiments of the invention

The present invention will be further described below in conjunction with the embodiments:

Example 1: Hydrogenation of benzaldehyde with pinacol borane borohydride catalyzed by o-methylanilinyl lithium

In a dehydration and deoxidation reaction bottle, add 20 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) under argon (0.1 mol%, the same below), then add 0.1596 mL of borane with a syringe and mix well. Then, 0.1016 mL of benzaldehyde was added by a syringe, and the mixture was stirred at room temperature. After 10 minutes of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol boric acid. Ester C ₆ H ₅ CH ₂ OB(OC(CH ₃ ) ₂ C(CH ₃ ) ₂ O). ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.36-7.23 (m, 5H, Ar-H), 4.92 (s, 2H, OCH ₂ ), 1.26 (s, 12H, CH ₃ ). ¹³ C NMR (101 MHz , CDCl ₃ ) δ 138.76 (Ar-C), 127.81 (Ar-C), 126.89 (Ar-C), 126.24 (Ar-C), 82.48 (OC), 66.20 (OCH ₂ ), 24.15 (CH ₃ ).

Substitution of o-methylanilinium lithium with an amine lithium compound of formula I results in almost no product, with a yield of less than 5%.

Example 2: Hydrogenation of p-Fluorobenzaldehyde with pinacol borane by hydrogenation of o-methylanilinyl lithium

In a dehydration and deoxidation reaction bottle, add 20 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) under argon (0.1 mol%, the same below), then add 0.1596 mL of borane with a syringe and mix well. Then, 0.1072 mL of p-fluorobenzaldehyde was added by a syringe, and the mixture was stirred at room temperature. After 10 min of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol. Borate p- FC ₆ H ₄ CH ₂ OB(OC(CH ₃ ) ₂ C(CH ₃ ) ₂ O). ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.34-7.29 (m, 2H, Ar-H), 7.04-6.98 (m, 2H, Ar-H), 4.87 (s, 2H, OCH2), 1.26 (s, 12H, CH3). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 161.71 (ds, Ar-C), 134.50 (d, J = 3.2 Hz, Ar-C), 128.14 (d, J = 8.1 Hz, Ar- C), 114.60 (ds, Ar-C), 82.54 (OC), 65.56 (OCH ₂ ), 24.11 (CH ₃ ).

Example 3: o-Methylaniline-based lithium catalyzed hydroboration of m-chlorobenzaldehyde with pinacol borane

In a dehydration and deoxidation reaction bottle, add 20 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) under argon (0.1 mol%, the same below), then add 0.1596 mL of borane with a syringe and mix well. Then, 0.0899 mL of m-chlorobenzaldehyde was added by a syringe, and the mixture was stirred at room temperature. After 10 minutes of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol. Borate m- Cl-C ₆ H ₄ CH ₂ OB(OC(CH ₃ ) ₂ C(CH ₃ ) ₂ O). ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.36 (s, 1H, Ar-H), 7.28-7.19 (m, 3H, Ar-H), 4.89 (s, 2H, OCH ₂ ), 1.27 (s, 12H , CH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 140.75 (Ar-C), 133.75 (Ar-C), 129.08 (Ar-C), 126.99 (Ar-C), 126.30 (Ar-C) , 124.17 (Ar-C), 82.61 (OC), 65.41 (OCH ₂ ), 24.05 (CH ₃ ).

Example 4: O-Methylaniline-based lithium catalyzed hydroboration of p-methylbenzaldehyde with pinacol borane

In a dehydration and deoxidation reaction bottle, add 20 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) under argon (0.1 mol%, the same below), then add 0.1596 mL of borane with a syringe and mix well. Then, 0.1184 mL of p-methylbenzaldehyde was added by a syringe, and the mixture was stirred at room temperature. After 10 minutes of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain a corresponding frequency. Alcohol borate p- Me-C ₆ H ₄ CH ₂ OB(OC(CH ₃ ) ₂ C(CH ₃ ) ₂ O). ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.24-7.22 (m, 2H, Ar-H), 7.13-7.11 (m, 2H, Ar-H), 4.87 (s, 2H, OCH ₂ ), 2.32 (s , 3H, Ar-CH ₃ ), 1.24 (s, 12H, CH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 136.51 (Ar-C), 135.79 (Ar-C), 128.49 (Ar-C) , 126.40 (Ar-C), 82.45 (OC), 66.13 (OCH ₂ ), 24.14 (CH ₃ ), 20.66 (CH ₃ ).

Example 4: O-Methylaniline-based lithium catalyzed hydroboration of o-methylbenzaldehyde with pinacol borane

In a dehydration and deoxidation reaction bottle, add 20 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) under argon (0.1 mol%, the same below), then add 0.1596 mL of borane with a syringe and mix well. Then, 0.1156 mL of o-methylbenzaldehyde was added by a syringe, and the mixture was stirred at room temperature. After 10 minutes of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain a corresponding frequency. Alcohol borate o- Me-C ₆ H ₄ CH ₂ OB(OC(CH ₃ ) ₂ C(CH ₃ ) ₂ O). ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.39 (dq, J = 7.2, 3.6 Hz, 1H, Ar-H), 7.18-7.11 (m, 3H, Ar-H), 4.92 (s, 2H, OCH ₂ ), 2.30 (s, 3H, Ar-CH ₃ ), 1.26 (s, 12H, CH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 136.69 (Ar-C), 135.13 (Ar-C), 129.49 (Ar-C), 126.86 (d, J = 25.25, Ar-C), 125.35 (Ar-C), 82.45 (OC), 64.49 (OCH ₂ ), 24.15 (CH ₃ ), 18.18 (CH ₃ ).

Example 5: O-Methylaniline-based lithium catalyzed hydroboration of 2,4,6-trimethylbenzaldehyde with pinacol borane

In a dehydration and deoxidation reaction bottle, add 40 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) under argon (0.2 mol%, the same below), then add 0.1596 mL of borane with a syringe and mix well. Then, 0.1475 mL of 2,4,6-trimethylbenzaldehyde was added by a syringe, and the mixture was stirred at room temperature. After 10 minutes of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure, that is, The corresponding pinacol borate 2,4,6-Me ₃ -C ₆ H ₂ CH ₂ OB(OC(CH ₃ ) ₂ C(CH ₃ ) ₂ O) was obtained. ¹ H NMR (400 MHz, CDCl ₃ ) δ 6.83 (s, 2H, Ar-H), 4.96 (s, 2H, OCH ₂ ), 2.38 (s, 6H, Ar-CH ₃ ), 2.25 (s, 3H, Ar-CH ₃ ), 1.26 (s, 12H, CH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 137.25 (Ar-C), 137.08 (Ar-C), 128.67 (Ar-C), 128.41 ( Ar-C), 82.28 (OC), 60.72 (OCH ₂ ), 24.15 (CH ₃ ), 20.49 (CH ₃ ), 18.95 (CH ₃ ).

Example 6: O-methylanilinyl lithium catalyzed borohydride hydrogenation of p-methoxybenzaldehyde with pinacol borane

In a dehydration and deoxidation reaction flask, 60 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) (0.3 mol%, the same below) was added under argon atmosphere, and then 0.1596 mL of borane was added by syringe, and the mixture was uniformly mixed. Then, 0.1214 mL of p-methoxybenzaldehyde was added by a syringe, and the mixture was stirred at room temperature. After 30 min of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain a corresponding frequency. Which alcohol borate p- MeO-C ₆ H ₂ CH ₂ OB(OC(CH ₃ ) ₂ C(CH ₃ ) ₂ O). ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.29-7.25 (m, 2H, Ar-H), 6.87-6.84 (m, 2H, Ar-H), 4.84 (s, 2H, OCH ₂ ), 3.78 (s , 3H, Ar-CH ₃ ), 1.21 (s, 12H, CH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 158.56 (Ar-C), 130.98 (Ar-C), 128.03 (Ar-C) , 113.19 (Ar-C), 82.38 (OC), 65.95 (OCH ₂ ), 54.74 (OCH ₃ ), 24.14 (CH ₃ ).

Example 7: Hydrogenation of 2-pyridinecarboxaldehyde with pinacolborane borohydride catalyzed by o-methylanilinium lithium

In a dehydration and deoxidation reaction bottle, add 20 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) under argon (0.1 mol%, the same below), then add 0.1596 mL of borane with a syringe and mix well. Then, 0.095 mL of 2-pyridinecarboxaldehyde was added by a syringe, and the mixture was stirred at room temperature. After 10 minutes of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol boron. Acid ester 2-C ₅ H ₄ NCOCH ₂ OB(OC(CH ₃ ) ₂ C(CH ₃ ) ₂ O). ¹ H NMR (400 MHz, CDCl ₃ ) δ 8.61 (d, J = 5.4 Hz, 1H, Ar-H), 7.91 (t, J = 7.7 Hz, 1H, Ar-H), 7.49-7.41 (m, 2H , Ar-H), 5.10 (s, 2H, OCH ₂ ), 1.32 (s, 12H, CH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 159.82 (Ar-C), 143.72 (Ar-C) , 139.56 (Ar-C), 123.39 (Ar-C), 120.09 (Ar-C), 81.04 (OC), 66.47 (OCH ₂ ), 25.47 (CH ₃ ).

Example 8: Hydrogenation of 2-thiophenecarboxaldehyde with pinacolborane borohydride catalyzed by o-methylanilinium lithium

In a dehydration and deoxidation reaction bottle, add 20 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) under argon (0.1 mol%, the same below), then add 0.1596 mL of borane with a syringe and mix well. Then, 0.092 mL of 2-thiophenecarboxaldehyde was added by a syringe, and the mixture was stirred at room temperature. After 10 min of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol boron. Acid ester 2-C ₄ H ₃ NCOCH ₂ OB(OC(CH ₃ ) ₂ C(CH ₃ ) ₂ O). ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.25 (d, J = 4.3 Hz, 1H, Ar-H), 7.02-6.94 (m, 2H, Ar-H), 5.04 (s, 2H, OCH ₂ ), 1.27 (s, 12H, CH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 141.97 (Ar-C), 126.59 (Ar-C), 125.89 (Ar-C), 125.51 (Ar-C), 83.14 (OC), 61.63 (OCH ₂ ), 24.63 (CH ₃ ).

Example 9: Hydrogenation of cyclohexylbenzaldehyde with pinacol borane borohydride catalyzed by o-methylanilinium lithium

In a dehydration and deoxidation reaction bottle, add 20 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) under argon (0.1 mol%, the same below), then add 0.1596 mL of borane with a syringe and mix well. Then, 0.095 mL of 2-pyridinecarboxaldehyde was added by a syringe, and the mixture was stirred at room temperature. After 10 minutes of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol boron. Acid ester C ₆ H ₅ COCH ₂ OB(OC(CH ₃ ) ₂ C(CH ₃ ) ₂ O). ¹ H NMR (400 MHz, CDCl ₃ ) δ 8.61 (d, J = 5.4 Hz, 1H, Ar-H), 7.91 (t, J = 7.7 Hz, 1H, Ar-H), 7.49-7.41 (m, 2H , Ar-H), 5.10 (s, 2H, OCH ₂ ), 1.32 (s, 12H, CH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 159.82 (Ar-C), 143.72 (Ar-C) , 139.56 (Ar-C), 123.39 (Ar-C), 120.09 (Ar-C), 81.04 (OC), 66.47 (OCH ₂ ), 25.47 (CH ₃ ).

Example 10: o-Methylaniline-based lithium catalyzed hydrofluorination of propionaldehyde with pinacol borane

In a dehydration and deoxidation reaction bottle, add 20 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) under argon (0.1 mol%, the same below), then add 0.1596 mL of borane with a syringe and mix well. Then, 0.072 mL of propionaldehyde was added by a syringe, and the mixture was stirred at room temperature. After 10 minutes of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol boric acid. Ester CH ₃ CH ₂ COCH ₂ OB(OC(CH ₃ ) ₂ C(CH ₃ ) ₂ O). ¹ H NMR (400 MHz, CDCl ₃ ) δ 3.80 (t, J = 6.6 Hz, 2H, OCH ₂ ), 1.63-1.54 (m, 2H, CH ₂ ), 1.25 (s, 12H, CH ₃ ), 0.91 ( t, J = 7.4 Hz, 3H, CH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 82.04 (OC), 66.02 (OCH ₂ ), 24.14 (CH ₃ CH ₂ ), 24.05 (CH ₃ ), 9.55 (CH ₂ CH ₃ ).

Example 11: O-Methylaniline-based lithium catalyzed hydroboration of n-heptanal with pinacol borane

In a dehydration and deoxidation reaction bottle, add 20 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) under argon (0.1 mol%, the same below), then add 0.1596 mL of borane with a syringe and mix well. Then, 0.1392 mL of n-heptanal was added by a syringe, and the mixture was stirred at room temperature. After 10 min of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol boron. Acid ester C ₆ H ₁₃ COCH ₂ OB(OC(CH ₃ ) ₂ C(CH ₃ ) ₂ O). ¹ H NMR (400 MHz, CDCl ₃ ) δ 3.82 (t, J = 8 Hz, 2H, OCH ₂ ), 1.52-1.58 (m, 2H, CH ₂ ), 1.27-1.34 (m, 8H, CH ₂ ), 1.24 (s, 12H, CH ₃ ), 0.87 (t, J = 8 Hz, 3H, CH ₃ ). ¹³ C NMR (100 MHz, CDCl ₃ ) δ 82.02 (OC), 64.40 (OCH ₂ ), 31.29 (CH ₂ ), 30.92 (CH ₂ ), 28.44 (CH ₂ ), 25.02 (CH ₂ ), 24.00 (CH ₃ ), 22.05 (CH ₂ ), 13.51 (CH ₃ ).

Example 12: Hydrogenation of acetophenone with pinacol borane borohydride catalyzed by o-methylanilinyl lithium

In a dehydration and deoxidation reaction bottle, add 40 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) (0.2 mol%) under argon atmosphere, then add 0.1596 mL of borane with a syringe, mix well, and then use 0.117 mL of acetophenone was added to the syringe, and the mixture was stirred at room temperature. After 20 min of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol borate. C ₆ H ₅ CH(CH ₃ )OB(OC(CH ₃ ) ₂ C(CH ₃ ) ₂ O). ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.38-7.21 (m, 5H, Ar-H), 5.24 (q, J = 6.5 Hz, 1H, OCH), 1.49 (d, J = 6.5 Hz, 3H, CH ₃ ), 1.22 (d, J = 11.9 Hz, 12H, CH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 144.09 (Ar-C), 127.71 (Ar-C), 126.62 (Ar-C), 124.86 (Ar-C), 82.26 (OC), 72.10 (OCH), 24.98 (CH ₃ ), 24.07 (d, J = 4.5 Hz, CH ₃ ).

Example 13: Hydrogenation of p-fluoroacetophenone with pinacol borane by hydrogenation of o-methylanilinyl lithium

In a dehydration and deoxidation reaction bottle, add 40 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) (0.2 mol%) under argon atmosphere, then add 0.1596 mL of borane with a syringe, mix well, and then use 0.1208 mL of p-fluoroacetophenone was added to the syringe, and the mixture was stirred at room temperature. After 20 min of reaction, the nuclear magnetic yield was 99%. Then, a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol borate. ester. ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.35-7.30 (m, 2H, Ar-H), 7.02-6.96 (m, 2H, Ar-H), 5.22 (q, J = 6.4 Hz, 1H, OCH) , 1.47 (d, J = 6.5 Hz, 3H, CH ₃ ), 1.22 (d, J = 11.6 Hz, 12H, CH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 161.94 (ds, Ar-C) , 140.34 (d, J = 3.1 Hz, Ar-C), 127.02 (d, J = 8.0 Hz, Ar-C), 114.93 (ds, Ar-C), 82.80 (OC), 72.00 (OCH), 25.40 ( CH ₃ ), 24.52 (d, J = 6.1 Hz, CH ₃ ).

Example 14: O-Methylaniline-based lithium catalyzed hydroboration of m-fluoroacetophenone with pinacol borane

In a dehydration and deoxidation reaction bottle, add 40 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) (0.2 mol%) under argon atmosphere, then add 0.1596 mL of borane with a syringe, mix well, and then use 0.1226 mL of m-fluoroacetophenone was added to the syringe, and the mixture was stirred at room temperature. After 20 min of reaction, the nuclear magnetic yield was 99%. Then, a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol boric acid. ester. ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.29-7.24 (m, 1H, Ar-H), 7.12-7.08 (m, 2H, Ar-H), 6.94-6.89 (m, 1H, Ar-H), 5.23 (q, J = 6.4 Hz, 1H, OCH), 1.48 (d, J = 6.5 Hz, 3H, CH ₃ ), 1.23 (d, J = 11.4 Hz, 12H, CH ₃ ). ¹³ C NMR (101 MHz , CDCl ₃ ) δ 162.85 (ds, Ar-C), 147.26 (d, J = 6.9 Hz, Ar-C), 129.67 (d, J = 8.2 Hz, Ar-C), 120.88 (d, J = 2.8 Hz , Ar-C), 113.87 (ds, Ar-C), 112.33 (ds, Ar-C), 82.87 (OC), 71.95 (d, J = 1.8 Hz, OCH), 25.30 (CH ₃ ), 24.52 (d , J = 4.2 Hz, CH ₃ ).

Example 15: Hydrogenation of p-chloroacetophenone with pinacol borane borohydride catalyzed by o-methylanilinyl lithium

In a dehydration and deoxidation reaction bottle, add 40 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) (0.2 mol%) under argon atmosphere, then add 0.1596 mL of borane with a syringe, mix well, and then use 0.1297 mL of p-chloroacetophenone was added to the syringe, and the mixture was stirred at room temperature. After 20 min of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol borate. ester. ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.31-7.26 (m, 4H, Ar-H), 5.21 (q, J = 6.4 Hz, 1H, OCH), 1.46 (d, J = 6.5 Hz, 3H, CH ₃ ), 1.22 (d, J = 11.4 Hz, 12H, CH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 142.62 (Ar-C), 132.26 (Ar-C), 127.83 (Ar-C), 126.29 (Ar-C), 82.35 (OC), 71.45 (OCH), 24.87 (CH ₃ ), 24.04 (d, J = 4.7 Hz, CH ₃ ).

Example 16: Lithium o-aniline lithium catalyzed hydroboration of p-methylacetophenone with pinacol borane

In a dehydration and deoxidation reaction flask, 60 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) (0.3 mol%) was added under argon atmosphere, and then 0.1596 mL of borane was added by syringe, and the mixture was uniformly mixed. 0.1335 mL of p-methylacetophenone was added to the syringe, and the mixture was stirred at room temperature. After 20 min of reaction, the nuclear magnetic yield was 99%. Then, a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol boron. Acid ester. ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.26-7.24 (m, 2H, Ar-H), 7.11-7.13 (m, 2H, Ar-H), 5.21 (q, J = 6.4 Hz, 1H, OCH) , 2.32 (s, 3H, Ar-CH ₃ ), 1.47 (d, J = 6.5 Hz, 3H, CH ₃ ), 1.22 (d, J = 10.4 Hz, 12H, CH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 141.17 (Ar-C), 136.17 (Ar-C), 128.38 (Ar-C), 124.82 (Ar-C), 82.21 (OC), 71.96 (OCH), 24.99 (CH ₃ ), 24.08 ( d, J = 3.7 Hz, CH ₃ ), 20.61 (s, Ar-CH ₃ ).

Example 17: Hydrogenation of 2-acetylthiophene with pinacol borane by hydrogenation of o-methylanilinyl lithium

In a dehydration and deoxidation reaction bottle, add 40 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) (0.2 mol%) under argon atmosphere, then add 0.1596 mL of borane with a syringe, mix well, and then use 0.1097 mL of 2-acetylthiophene was added to the syringe, and the mixture was stirred at room temperature. After 20 minutes of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol borate. ¹ H NMR (400 MHz, CDCl ₃ ) δ 7.20-7.18 (m, 1H, Ar-H), 6.97-6.91 (m, 2H, Ar-H), 5.48 (q, J = 6.4 Hz, 1H, OCH) , 1.60 (d, J = 6.4 Hz, 3H, CH ₃ ), 1.24 (d, J = 4.9 Hz, 12H, CH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 147.72 (Ar-C), 125.90 (Ar-C), 123.63 (Ar-C), 122.79 (Ar-C), 82.44 (OC), 68.15 (OCH), 24.58 (CH ₃ ), 24.09 (d, J = 9.8 Hz, CH ₃ ).

The o-methylanilinium lithium was replaced with metallic lithium, and the product could not be obtained.

Example 18: Hydrogenation of methyl isopropyl ketone with pinacol borane borohydride catalyzed by o-methylanilinium lithium

In a dehydration and deoxidation reaction flask, 60 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) (0.3 mol%) was added under argon atmosphere, and then 0.1596 mL of borane was added by syringe, and the mixture was uniformly mixed. 0.1072 mL of methyl isopropyl ketone was added to the syringe, and the mixture was stirred at room temperature. After 30 min of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol. Borate ester. ¹ H NMR (400 MHz, CDCl ₃ ) δ 3.94 (p, J = 6.2 Hz, 1H, OCH), 1.66 (dq, J = 13.5, 6.8 Hz, 1H, CH ₃ CH), 1.25 (s, 12H, CH ₃ ), 1.14 (d, J = 6.3 Hz, 3H, CH ₃ ), 0.91-0.85 (m, 6H, CHCH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 82.34 (OC), 75.40 (OCH) , 34.25 (OCHCH), 24.50 (d, J = 7.4 Hz, CH ₃ ), 19.30 (CH ₃ ), 18.10 (CH ₃ ), 17.74 (CH ₃ ).

Example 19: Hydrogenation of 4-heptanone with pinacol borane by hydrogenation of o-methylanilinyl lithium

In a dehydration and deoxidation reaction flask, 80 ul of o-methylanilinium lithium in tetrahydrofuran solution (0.05 M) (0.4 mol%) was added under argon atmosphere, and then 0.1596 mL of borane was added by syringe, and the mixture was uniformly mixed. 0.1398 mL of 4-heptanone was added to the syringe, and the mixture was stirred at room temperature. After 40 min of reaction, the nuclear magnetic yield was 99%, and then a small amount of tetrahydrofuran and excess borane were removed under reduced pressure to obtain the corresponding pinacol borate. ¹ H NMR (400 MHz, CDCl ₃ ) δ 4.03 (td, J = 8.0, 3.9 Hz, 1H, CH), 1.51 - 1.31 (m, 8H, CH ₂ ), 1.24 (s, 12H, CH ₃ ), 0.90 (t, J = 7.1 Hz, 6H, CH ₃ ). ¹³ C NMR (101 MHz, CDCl ₃ ) δ 81.82 (OC), 73.55 (OCH), 38.18 (CH2), 23.97 (CH ₃ ), 18.10 (CH ₃ ), 13.48 (CH ₃ ).

The present inventors have found for the first time that o-methylanilinyl lithium can catalyze the borohydride hydrogenation of aldehydes/ketones with extremely high catalytic activity and has a very wide practical range of substrates. Cheap catalysts, as well as lower catalyst usage and mild catalytic conditions, offer possibilities for industrial applications.

Claims

The use of o-methylanilinium lithium for catalyzing the borohydride hydroboration reaction of a carbonyl compound; the carbonyl compound is selected from the group consisting of an aromatic aldehyde, a heterocyclic aldehyde, a fatty aldehyde, an aromatic ketone, a heterocyclic ketone or an aliphatic ketone.
The use according to claim 1, wherein the hydroboration reaction comprises the steps of:

In an anhydrous and oxygen-free environment, under a noble gas atmosphere, borane is added to the reaction bottle subjected to dehydration and deoxidation treatment, then o-methylanilinyl lithium is added, uniformly mixed, and then a carbonyl compound is added to cause a hydroboration reaction.
The use according to claim 1, wherein the borane is selected from the group consisting of pinacol borane;

The chemical structure of the aromatic aldehyde is as follows:

The chemical structure of the aromatic ketone is as follows:

Wherein R, R' are independently selected from the group consisting of an electron withdrawing group or an electron donating group;

The heterocyclic aldehyde is selected from the group consisting of 2 pyridine formaldehyde or 2- thiophene formaldehyde;

The fatty aldehyde is selected from the group consisting of cyclohexylformaldehyde, propionaldehyde, and n-heptanal;

The heterocyclic ketone is selected from 2-acetylthiophene;

The fatty ketone is selected from the group consisting of methyl isopropyl ketone and 4-heptanone.
The use according to Claim 1, characterized in that the o-methylanilinium lithium is used in an amount of from 0.1 to 0.4% by mole based on the mole of the carbonyl compound, and the molar ratio of the carbonyl compound to borane is 1:1.1.
The use according to claim 1, characterized in that the temperature of the hydroboration reaction is room temperature for a period of 10 to 40 minutes.
A method for preparing a borate ester, comprising the steps of:

In an anhydrous oxygen-free environment, in an inert gas atmosphere, borane is added to the reaction bottle subjected to dehydration and deoxidation treatment, then the catalyst o-methylanilinyl lithium is added, uniformly mixed, and then a carbonyl compound is added to cause a hydroboration reaction, and the exposure is carried out. The reaction is terminated in air to give a borate; the carbonyl compound is selected from the group consisting of an aromatic aldehyde, a heterocyclic aldehyde, a fatty aldehyde, an aromatic ketone, a heterocyclic ketone or an aliphatic ketone.
The method for preparing a borate ester according to claim 6, wherein the chemical structure of the aromatic aldehyde is as follows:

The chemical structure of the aromatic ketone is as follows:

Wherein R, R' are independently selected from the group consisting of an electron withdrawing group or an electron donating group;

The heterocyclic aldehyde is selected from the group consisting of 2 pyridine formaldehyde or 2- thiophene formaldehyde;

The fatty aldehyde is selected from the group consisting of cyclohexylformaldehyde, propionaldehyde, and n-heptanal;

The heterocyclic ketone is selected from 2-acetylthiophene;

The fatty ketone is selected from the group consisting of methyl isopropyl ketone and 4-heptanone.
The method of producing a borate ester according to claim 6, wherein the borane is selected from the group consisting of pinacol borane.
The method for producing a borate ester according to claim 6, wherein the catalyst is used in an amount of from 0.1 to 0.4% by mole based on the mole of the carbonyl compound, and the molar ratio of the carbonyl compound to borane is 1:1.1.
The method for producing a borate ester according to claim 6, wherein the temperature of the hydroboration reaction is room temperature for a period of 10 to 40 minutes.