Application of 4-MePhNHLi in catalyzing hydroboration reaction of imine and borane

Abstract

The present invention relates to an application of 4-MePhNHLi, in particular, to an application of 4-MePhNHLi in catalyzing hydroboration reaction of imine and borane. A catalyst, borane, and imine are stirred and mixed uniformly in sequence for reaction for 1-2 hours, the reaction is terminated by exposure to air, and the solvent in the reaction liquid is removed under reduced pressure to obtain borate esters having different substituents. According to the present invention, 4-MePhNHLi can catalyze hydroboration reaction of imine and borane at high activity at room temperature, the amount of catalyst is only 4-5 mol % of the molar mass of imine, and the reaction can reach a yield of more than 90%; compared with an existing catalytic system, simple 4-MePhNHLi is used, the reaction conditions are mild, and the yield of borate esters having different substituents can reach 99% in optimized conditions.

Claims

1. A method of preparing a borate ester comprising: reacting an imine with a borane in an organic solvent and in the presence of 4-MePhNHLi as a catalyst at room temperature under anhydrous, oxygen-free, and inert gas conditions for 1-2 hours; and stirring in air to stop reaction and to obtain the borate ester.

2. The method of claim 1, wherein: the imine has the following structure: ##STR00004## the borane is pinacol borane; the borate ester has the following structure: ##STR00005## R.sub.1 and R.sub.2 are independently selected from the group consisting of halogen, methyl and methoxy.

3. The method of claim 1, wherein the organic solvent is tetrahydrofuran.

4. The method of claim 1, wherein an amount of 4-MePhNHLi is 4% to 5% of a molar amount of the imine.

5. The method of claim 1, wherein a molar ratio of the imine to the borane is 1:1 to 1:1.2.

6. The method of claim 5, wherein the molar ratio of the imine to the borane is 1:1.2.

Description

EMBODIMENTS OF THE INVENTION

(1) The present invention will be further described in combination with the following embodiments:

Example 1 Catalytic Hydroboration Reaction of Biphenylaniline and Pinacol Borane by 4-MePhNHLi

(2) In a reaction flask, which was treated by dehydration and deoxidation, 0.5 mmol of biphenylaniline and 100 μl of THF were added under the protection of argon. 0.5 mmol (0.0726 mL) of borane was added with a pipette gun and mixed well. Finally, 34.4 μl of 4-MePhNHLi tetrahydrofuran solution (0.7273 M) (5 mol % amount) was added. The reaction was carried out for 2 hours. A drop of the reaction solution was taken and added to an NMR tube. CDCl.sub.3 was then added to the NMR tube. The conversion rate calculated based on .sup.1H is 91%. .sup.1H NMR data of the product is: .sup.1H NMR (CDCl.sub.3, 400 MHz) δ: 7.29-7.12 (m, 9H), 6.88-6.84 (t, 1H), 4.69 (s, 2H), 1.29 (s, 12H).

Example 2 Catalytic Hydroboration Reaction of Biphenylaniline and Pinacol Borane by 4-MePhNHLi

(3) In a reaction flask, which was treated by dehydration and deoxidation, 0.5 mmol of biphenylaniline and 100 μl of THF were added under the protection of argon. 0.6 mmol (0.0871 mL) of borane was added with a pipette gun and mixed well. Finally, 34.4 μl of 4-MePhNHLi tetrahydrofuran solution (0.7273 M) (5 mol % amount) was added. The reaction was carried out for 1 hour. A drop of the reaction solution was taken and added to an NMR tube. CDCl.sub.3 was then added to the NMR tube. The conversion rate calculated based on 41 is 96%. .sup.1H NMR data of the product is: .sup.1H NMR (CDCl.sub.3, 400 MHz) δ: 7.29-7.12 (m, 9H), 6.88-6.84 (t, 1H), 4.69 (s, 1H), 1.29 (s, 12H).

Example 3 Catalytic Hydroboration Reaction of Biphenylaniline and Pinacol Borane by 4-MePhNHLi

(4) In a reaction flask, which was treated by dehydration and deoxidation, 0.5 mmol of biphenylaniline and 100 μl of THF were added under the protection of argon. 0.6 mmol (0.0871 mL) of borane was added with a pipette gun and mixed well. Finally, 34.4 μl of 4-MePhNHLi tetrahydrofuran solution (0.7273 M) (5 mol % amount) was added. The reaction was carried out for 2 hours. A drop of the reaction solution was taken and added to an NMR tube. CDCl.sub.3 was then added to the NMR tube. The conversion rate calculated based on .sup.1H is 99%. .sup.1H NMR data of the product is: .sup.1H NMR (CDCl.sub.3, 400 MHz) δ: 7.29-7.12 (m, 9H), 6.88-6.84 (t, 1H), 4.69 (s, 2H), 1.29 (s, 12H).

(5) If 4-methoxyaniline lithium was replaced with the lithium compound of formula I, a hydroboration product could not be obtained.

(6) ##STR00003##

Example 4 Catalytic Hydroboration Reaction of Biphenylaniline and Pinacol Borane by 4-MePhNHLi

(7) In a reaction flask, which was treated by dehydration and deoxidation, 0.5 mmol of biphenylaniline and 100 μl of THF were added under the protection of argon. 0.6 mmol (0.0871 mL) of borane was added with a pipette gun and mixed well. Finally, 27.5 μl of 4-MePhNHLi tetrahydrofuran solution (0.7273 M) (4 mol % amount) was added. The reaction was carried out for 2 hours. A drop of the reaction solution was taken and added to an NMR tube. CDCl.sub.3 was then added to the NMR tube. The conversion rate calculated based on .sup.1H is 97%. .sup.1H NMR data of the product is: .sup.1H NMR (CDCl.sub.3, 400 MHz) δ: 7.29-7.12 (m, 9H), 6.88-6.84 (t, 1H), 4.69 (s, 2H), 1.29 (s, 12H).

Example 5 Catalytic Hydroboration Reaction of N-(p-Methylbenzylidene) Aniline and Pinacol Borane by 4-MePhNHLi

(8) In a reaction flask, which was treated by dehydration and deoxidation, 0.5 mmol of N-(p-methylbenzylidene) aniline and 100 μl of THF were added under the protection of argon. 0.6 mmol (0.0871 mL) of borane was added with a pipette gun and mixed well. Finally, 34.4 of 4-MePhNHLi tetrahydrofuran solution (0.7273 M) (5 mol % amount) was added. The reaction was carried out for 2 hours. A drop of the reaction solution was taken and added to an NMR tube. CDCl.sub.3 was then added to the NMR tube. The conversion rate calculated based on .sup.1H is 99%. .sup.1H NMR data of the product is: .sup.1H NMR (CDCl.sub.3, 400 MHz) δ: 7.23-7.08 (m, 8H), 6.89-6.85 (t, 1H), 4.66 (s, 2H), 2.31 (s, 3H), 1.30 (s, 12H).

Example 6 Catalytic Hydroboration Reaction of N-(p-Methoxybenzylidene) Aniline and Pinacol Borane by 4-MePhNHLi

(9) In a reaction flask, which was treated by dehydration and deoxidation, 0.5 mmol of N-(p-methoxybenzylidene) aniline and 100 μl of THF were added under the protection of argon. 0.6 mmol (0.0871 mL) of borane was added with a pipette gun and mixed well. Finally, 34.4 μl of 4-MePhNHLi tetrahydrofuran solution (0.7273 M) (5 mol % amount) was added. The reaction was carried out for 2 hours. A drop of the reaction solution was taken and added to an NMR tube. CDCl.sub.3 was then added to the NMR tube. The conversion rate calculated based on .sup.1H is 99%. .sup.1H NMR data of the product is: .sup.1H NMR (CDCl.sub.3, 400 MHz) δ: 7.22-7.13 (d, 6H), 6.89-6.80 (d, 3H), 4.63 (s, 2H), 3.77 (s, 3H), 1.30 (s, 12H).

Example 7 Catalytic Hydroboration Reaction of N-(4-Fluorobenzylidene) Aniline and Pinacol Borane by 4-MePhNHLi

(10) In a reaction flask, which was treated by dehydration and deoxidation, 0.5 mmol of N-(4-fluorobenzylidene) aniline and 100 μl of THF were added under the protection of argon. 0.6 mmol (0.0871 mL) of borane was added with a pipette gun and mixed well. Finally, 34.4 μl of 4-MePhNHLi tetrahydrofuran solution (0.7273 M) (5 mol % amount) was added. The reaction was carried out for 2 hours. A drop of the reaction solution was taken and added to an NMR tube. CDCl.sub.3 was then added to the NMR tube. The conversion rate calculated based on .sup.1H is 99%. .sup.1H NMR data of the product is: .sup.1H NMR (CDCl.sub.3, 400 MHz) δ: 7.22-7.15 (d, 6H), 6.98-6.94 (d, 3H), 4.66 (s, 2H), 1.30 (s, 12H).

Example 8 Catalytic Hydroboration Reaction of N-(4-Chlorobenzylidene) Aniline and Pinacol Borane by 4-MePhNHLi

(11) In a reaction flask, which was treated by dehydration and deoxidation, 0.5 mmol of N-(4-chlorobenzylidene) aniline and 100 μl of THF were added under the protection of argon. 0.6 mmol (0.0871 mL) of borane was added with a pipette gun and mixed well. Finally, 34.4 μl of 4-MePhNHLi tetrahydrofuran solution (0.7273 M) (5 mol % amount) was added. The reaction was carried out for 2 hours. A drop of the reaction solution was taken and added to an NMR tube. CDCl.sub.3 was then added to the NMR tube. The conversion rate calculated based on .sup.1H is 99%. .sup.1H NMR data of the product is: .sup.1H NMR (CDCl.sub.3, 400 MHz) δ: 7.20-7.14 (d, 6H), 6.99-6.93 (d, 3H), 4.64 (s, 2H), 1.30 (s, 12H).

Example 9 Catalytic Hydroboration Reaction of N-(4-Bromobenzylidene) Aniline and Pinacol Borane by 4-MePhNHLi

(12) In a reaction flask, which was treated by dehydration and deoxidation, 0.5 mmol of N-(4-bromobenzylidene) aniline and 100 μl of THF were added under the protection of argon. 0.6 mmol (0.0871 mL) of borane was added with a pipette gun and mixed well. Finally, 34.4 of 4-MePhNHLi tetrahydrofuran solution (0.7273 M) (5 mol % amount) was added. The reaction was carried out for 2 hours. A drop of the reaction solution was taken and added to an NMR tube. CDCl.sub.3 was then added to the NMR tube. The conversion rate calculated based on .sup.1H is 99%. .sup.1H NMR data of the product is: .sup.1H NMR (CDCl.sub.3, 400 MHz) δ: 7.24-7.16 (d, 6H), 6.97-6.93 (d, 3H), 4.63 (s, 2H), 1.31 (s, 12H).

Example 10 Catalytic Hydroboration Reaction of Benzylidene-p-Toluidine and Pinacol Borane by 4-MePhNHLi

(13) In a reaction flask, which was treated by dehydration and deoxidation, 0.5 mmol of benzylidene-p-toluidine and 100 μl of THF were added under the protection of argon. 0.6 mmol (0.0871 mL) of borane was added with a pipette gun and mixed well. Finally, 34.4 of 4-MePhNHLi tetrahydrofuran solution (0.7273 M) (5 mol % amount) was added. The reaction was carried out for 2 hours. A drop of the reaction solution was taken and added to an NMR tube. CDCl.sub.3 was then added to the NMR tube. The conversion rate calculated based on .sup.1H is 99%. .sup.1H NMR data of the product is: .sup.1H NMR (CDCl.sub.3, 400 MHz) δ: 7.32-7.28 (d, 5H), 7.10-7.08 (d, 2H), 6.64-6.60 (d, 2H), 4.62 (s, 2H), 1.31 (s, 12H).

Example 11 Catalytic Hydroboration Reaction of N-(Benzylidene)-4-Fluoroaniline and Pinacol Borane by 4-MePhNHLi

(14) In a reaction flask, which was treated by dehydration and deoxidation, 0.5 mmol of N-(benzylidene)-4-fluoroaniline and 100 μl of THF were added under the protection of argon. 0.6 mmol (0.0871 mL) of borane was added with a pipette gun and mixed well. Finally, 34.4 of 4-MePhNHLi tetrahydrofuran solution (0.7273 M) (5 mol % amount) was added. The reaction was carried out for 2 hours. A drop of the reaction solution was taken and added to an NMR tube. CDCl.sub.3 was then added to the NMR tube. The conversion rate calculated based on .sup.1H is 99%. .sup.1H NMR data of the product is: .sup.1H NMR (CDCl.sub.3, 400 MHz) δ: 7.24-7.02 (d, 7H), 6.75-6.70 (d, 2H), 4.66 (s, 2H), 1.32 (s, 12H).

Example 12 Catalytic Hydroboration Reaction of N-(Benzylidene)-4-Chloroaniline and Pinacol Borane by 4-MePhNHLi

(15) In a reaction flask, which was treated by dehydration and deoxidation, 0.5 mmol of N-(benzylidene)-4-chloroaniline and 100 μl of THF were added under the protection of argon. 0.6 mmol (0.0871 mL) of borane was added with a pipette gun and mixed well. Finally, 34.4 μl of 4-MePhNHLi tetrahydrofuran solution (0.7273 M) (5 mol % amount) was added. The reaction was carried out for 2 hours. A drop of the reaction solution was taken and added to an NMR tube. CDCl.sub.3 was then added to the NMR tube. The conversion rate calculated based on .sup.1H is 99%. .sup.1H NMR data of the product is: .sup.1H NMR (CDCl.sub.3, 400 MHz) δ: 7.26-7.05 (d, 7H), 6.74-6.69 (d, 2H), 4.61 (s, 2H), 1.30 (s, 12H).

Example 13 Catalytic Hydroboration Reaction of N-(Benzylidene)-4-Bromoaniline and Pinacol Borane by 4-MePhNHLi

(16) In a reaction flask, which was treated by dehydration and deoxidation, 0.5 mmol of N-(benzylidene)-4-bromoaniline and 100 μl of THF were added under the protection of argon. 0.6 mmol (0.0871 mL) of borane was added with a pipette gun and mixed well. Finally, 34.4 μl of 4-MePhNHLi tetrahydrofuran solution (0.7273 M) (5 mol % amount) was added. The reaction was carried out for 2 hours. A drop of the reaction solution was taken and added to an NMR tube. CDCl.sub.3 was then added to the NMR tube. The conversion rate calculated based on .sup.1H is 99%. .sup.1H NMR data of the product is: .sup.1H NMR (CDCl.sub.3, 400 MHz) δ: 7.27-7.03 (d, 7H), 6.76-6.71 (d, 2H), 4.62 (s, 2H), 1.30 (s, 12H).