A method for preparing an organoboron ester compound catalyzed by diethylzinc

Abstract

The present invention provides a method for preparing an organoborate compound catalyzed by diethylzinc, belonging to the technical field of the preparation of borate compounds, and capable of solving the urgent problems to be solved in the preparation method of this ester compound. The method includes mixing an ester compound with a boron hydride under an inert atmosphere, and then adding diethylzinc; the reaction system reacts at 60-80 °C for 8-12 h, and then is exposed to air to terminate the reaction to obtain the borate compound. The inert atmosphere is nitrogen, and the ester compound is an aliphatic ester compound, an aromatic ester compound, or a cyclic ester compound. The present invention solves the urgent problems such as the complex preparation of the catalyst used in the preparation method of this ester compound, the large amount of the catalyst used, and the long reaction time.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of borate compounds, and particularly to a method for preparing an organoborate compound catalyzed by diethylzinc. Background Art

[0002] Ester compounds play an important role in the synthesis of fine chemicals and pharmaceuticals, and are also ubiquitous in chemical raw materials such as vegetable oils and cellulose and some valuable renewable fuels. They are not only often used as green solvents in many chemical reactions, but they can also be regarded as protecting groups or synthetic precursors of the corresponding diols.

[0003] Catalytic hydrogenation is a commonly used method for converting unsaturated organic molecules into corresponding value-added products. However, it is usually accompanied by high pressure, flammable hydrogen gas, relatively high reaction temperature, etc. In addition, different from aldehydes and ketones, ester compounds have high kinetic stability towards the addition of hydrides, and they are inert to mild reducing agents (such as NaBH4), and usually require stronger reducing agents such as BH3 and LiAlH4. The handling of such reagents poses certain risks, and the selectivity is often poor during reduction. Against this background, boranes are often used as an alternative reducing agent to avoid high-pressure hydrogenation reactions using flammable hydrogen gas. Pinacol borane (HBpin) has the advantages of air stability, low cost, good functional group tolerance, etc. Therefore, the catalytic hydroboration of ester compounds is a meaningful and possible alternative method to the corresponding hydrogenation.

[0004] The catalysis for the synthesis of borate ester compounds reported in the literature is catalyzed by metallic zinc (D. Mukherjee, A. K. Wiegand, T. P. Spaniol and J. Okuda, Dalton Trans, 2017, 46, 6183 - 6186.). In this method, under an inert atmosphere, using a zinc borate complex as a catalyst, the hydroboration reaction of ethyl acetate was carried out at 60 °C for 35 h. The catalyst used in this method is relatively complex to prepare. First, a solution of [Zn{N(SiHMe2)2}2] (0.289 g, 0.876 mmol) and Me4TACD (0.200 g, 0.876 mmol) in 5 mL of THF was stirred for 10 minutes, and then BPh3 (0.212 g, 0.876 mmol) in 2 mL of THF was added to this mixture and stirred for another 24 h. During this period, a small amount of white solid precipitated and was removed by filtration. Then the filtrate was evaporated under reduced pressure to obtain a colorless solid. Finally, the obtained solid was washed with n-pentane (3×5 mL) and dried in vacuo to obtain an analytically pure zinc borate complex (0.387 g, 0.578 mmol, 66%), which was a colorless powder. In addition, in this method, during the reaction process, the dosage of the catalyst is relatively large, being 10% of the molar amount of the ester compound, and the reaction time is relatively long.

[0005] Using a commercially available catalyst, reducing the dosage of the catalyst, and shortening the reaction time are the difficult problems that urgently need to be solved in the preparation method of this ester compound. Summary of the Invention

[0006] The object of the present invention is to provide a method for preparing an organoborate ester compound catalyzed by diethylzinc, which uses a commercially available catalyst, reduces the dosage of the catalyst, and shortens the reaction time, thereby solving the difficult problems that urgently need to be solved in the preparation method of this ester compound.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing an organoborate ester compound catalyzed by diethylzinc, which is characterized by comprising the following steps:

[0009] Step 1: Under an inert atmosphere, an ester compound and a borohydride are mixed, and then diethylzinc is added;

[0010] Step 2: The reaction system reacts at 60 - 80 °C for 8 - 12 h, and then is exposed to air to terminate the reaction, obtaining the borate ester compound.

[0011] The inert atmosphere in Step 1 is nitrogen.

[0012] The ester compound is an aliphatic ester compound, an aromatic ester compound, or a cyclic ester compound.

[0013] The aliphatic ester compound is ethyl acetate, cyclohexyl acetate, isobutyl isobutyrate, or methyl methacrylate.

[0014] The aromatic ester compound is benzyl benzoate, phenyl formate, phenyl benzoate, methyl benzoate, phthalide, methyl p-toluate, methyl p-fluorobenzoate, or methyl p-nitrobenzoate.

[0015] The cyclic ester compound is 4-valerolactone, or ε-caprolactone.

[0016] The borohydride is pinacolborane.

[0017] The molar ratio of the ester compound to the borohydride is 1:(2 - 2.2).

[0018] The molar amount of diethylzinc is 3 - 5% of the molar amount of the ester compound.

[0019] The present invention provides a method for preparing an organoborate compound catalyzed by diethylzinc. Zinc is a common metal, rather than a rare earth metal, which is easy to obtain, inexpensive, and the catalyst diethylzinc has been commercialized. The amount of the catalyst used is significantly reduced, and the reaction time is shortened, solving the problems such as the complex preparation of the catalyst used in the preparation method of this type of ester compound, the large amount of the catalyst used, and the long reaction time. Detailed Embodiments

[0020] Next, in combination with the embodiments of the present invention, the technical solutions in the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0021] Example 1

[0022] According to the technical solution of the present invention, a specific application method includes the following steps:

[0023] (1) Under an inert atmosphere, that is, in a glove box protected by nitrogen, the ester compound and borane are mixed according to the molar ratio, and then the catalyst diethylzinc is added;

[0024] (2) The mixed system obtained in (1) is reacted at 60 - 80 °C for 8 - 12 h, and then exposed to air to terminate the reaction, obtaining the borate compound.

[0025] Among them, the borane is preferably pinacolborane, and the reaction formula is as follows:

[0026]

[0027] Among them, R 1 is selected from any one of H, alkyl, or aryl, and R 2 is selected from alkyl or aryl.

[0028] The reaction of diethylzinc catalyzing ethyl acetate and pinacol borane

[0029] Step 1: In a nitrogen-protected glove box, mix ethyl acetate (1 mmol) and pinacol borane (2.1 mmol) in a 10 mL reaction flask, and then add 0.05 mL (5 mmol%) of 1 mol / L diethylzinc with a syringe;

[0030] Step 2: Heat the resulting mixed system in an oil bath at 60 °C for 12 h, then expose it to air to terminate the reaction, obtain the borate ester compound, dissolve the product with CDCl3, take samples, and perform 1 1H NMR and 13 13C NMR spectrum tests. The NMR data of the obtained product are as follows:

[0031] 1 1H NMR (400 MHz, CDCl3) δ 3.83 (q, J = 7.0 Hz, 2H, MeCH2OBpin), 1.18 (d, J = 2.5 Hz, 12H, BOCMe2), 1.14 (s, 3H, MeCH2OBpin).

[0032] 13 13C NMR (101 MHz, CDCl3) δ 81.03, 60.06, 23.58, 16.18.

[0033] The calculated yield of the product 1 1H-NMR is 99%.

[0034] Example 2

[0035] Prepare the borate ester compound through the process of Example 1, with the only difference being adding 0.03 mL (3 mmol%) of 1 mol / L diethylzinc, then heating in an oil bath at 60 °C for 12 h, exposing it to air to terminate the reaction, obtaining the borate ester compound, dissolving the product with CDCl3, and the calculated yield of the product 1 1H-NMR is 90%.

[0036] Example 3

[0037] The borate compound was prepared by the process of Example 1, except that 0.04 mL (4 mmol%) of 1 mol / L diethylzinc was added, and then it was heated in an oil bath at 60 °C for 12 h, and the reaction was terminated by exposure to air. The resulting borate compound was dissolved in CDCl3, and the product 1 The yield of 1H-NMR was 94%.

[0038] Example 4

[0039] The borate compound was prepared by the process of Example 1, except that it was heated in an oil bath at 60 °C for 8 h, and the reaction was terminated by exposure to air. The resulting borate compound was dissolved in CDCl3, and the product 1 The yield of 1H-NMR was 86%.

[0040] Example 5

[0041] The borate compound was prepared by the process of Example 1, except that it was heated in an oil bath at 60 °C for 10 h, and the reaction was terminated by exposure to air. The resulting borate compound was dissolved in CDCl3, and the product 1 The yield of 1H-NMR was 92%.

[0042] Example 6

[0043] The borate compound was prepared by the process of Example 1, except that the amount of pinacolborane added was 2 mmol, and then it was heated in an oil bath at 60 °C for 12 h, and the reaction was terminated by exposure to air. The resulting borate compound was dissolved in CDCl3, and the product 1 The yield of 1H-NMR was 96%.

[0044] Example 7

[0045] The borate compound was prepared by the process of Example 1, except that the amount of pinacolborane added was 2.2 mmol, and then it was heated in an oil bath at 60 °C for 12 h, and the reaction was terminated by exposure to air. The resulting borate compound was dissolved in CDCl3, and the product 1 The yield of 1H-NMR was 99%.

[0046] Example 8

[0047] Reaction of cyclohexyl acetate with pinacolborane catalyzed by diethylzinc

[0048] Step 1: In a glove box under nitrogen protection, cyclohexyl acetate (1 mmol) and pinacolborane (2.1 mmol) were mixed in a 10 mL reaction flask, and then 0.05 mL (5 mmol%) of 1 mol / L diethylzinc was added with a syringe;

[0049] Step 2: Heat the obtained mixed system in an oil bath at 60 °C for 12 h, then expose it to air to terminate the reaction, obtaining a borate compound. Dissolve the product in CDCl3, take samples, and perform 1 1H NMR and 13 13C NMR spectrum tests. The NMR data of the obtained product are as follows:

[0050] 1 1H NMR (400 MHz, CDCl3) δ 3.91 (q, J = 4.8 Hz, 1H, CyOBpin), 3.82 (q, J = 7.1 Hz, 2H, MeCH2OBpin), 1.79 - 1.73 (m, 2H, CyOBpin), 1.64 (dt, J = 8.1, 4.4 Hz, 2H, CyOBpin), 1.43 (dt, J = 11.8, 4.5 Hz, 2H, CyOBpin), 1.30 (d, J = 9.0 Hz, 1H, CyOBpin), 1.24 (d, J = 11.2 Hz, 3H, CyOBpin), 1.18 (s, 24H, BOCMe2), 1.14 (s, 3H, MeCH2OBpin).

[0051] 13 13C NMR (101 MHz, CDCl3) δ 81.55, 81.38, 71.57, 59.62, 33.23, 24.45, 23.55, 22.79, 16.18.

[0052] The calculated 1 yield of 1H-NMR is 99%.

[0053] Example 9

[0054] Reaction of isobutyl isobutyrate with pinacol borane catalyzed by diethylzinc

[0055] Step 1: In a glove box under nitrogen protection, mix isobutyl isobutyrate (1 mmol) and pinacol borane (2.1 mmol) in a 10 mL reaction flask, and then add 0.05 mL (5 mmol%) of 1 mol / L diethylzinc using a syringe;

[0056] Step 2: Different from other examples, heat the obtained mixed system in an oil bath at 80 °C for 12 h, then expose it to air to terminate the reaction, obtaining a borate compound. Dissolve the product in CDCl3, take samples, and perform 1 1H NMR and 13 13C NMR spectrum tests. The NMR data of the obtained product are as follows:

[0057] 11H NMR (400 MHz, CDCl3) δ 3.54 (d, J = 6.5 Hz, 2H, CH2OBpin), 1.74 (dt, J = 13.3, 6.7 Hz, 1H, CHMe2), 1.18 (d, J = 2.9 Hz, 12H, BOCMe2), 0.82 (d, J = 6.7 Hz, 6H, CHMe2).

[0058] 13 13C NMR (101 MHz, CDCl3) δ 81.56, 70.36, 28.82, 23.78, 23.56, 17.73.

[0059] The calculated product 1 The yield of 1H-NMR is 99%.

[0060] Example 10

[0061] Reaction of methyl methacrylate with pinacol borane catalyzed by diethylzinc

[0062] Step 1: In a nitrogen-protected glove box, methyl methacrylate (1 mmol) and pinacol borane (2.1 mmol) were mixed in a 10 mL reaction flask, and then 0.05 mL (5 mmol%) of 1 mol / L diethylzinc was added by syringe;

[0063] Step 2: The resulting mixture was heated in an oil bath at 60 °C for 12 h, and then the reaction was terminated by exposure to air to obtain a borate compound. The product was dissolved in CDCl3, sampled, and subjected to 1 1H NMR and 13 13C NMR spectral tests. The NMR data of the obtained product are as follows:

[0064] 1 1H NMR (400 MHz, CDCl3) δ 4.90 (s, 1H, C=CH2), 4.75 (s, 1H, C=CH2), 4.18 (s, 2H, CH2OBpin), 3.53 (s, 3H, MeOBpin), 1.65 (s, 3H, MeC=CH2), 1.18 (s, 24H, BOCMe2).

[0065] 13 13C NMR (101 MHz, CDCl3) δ 141.66, 108.99, 81.78, 67.25, 51.58, 23.59, 23.56, 17.95.

[0066] The calculated product 1 The yield of 1H-NMR is 99%.

[0067] Example 11

[0068] Reaction of Benzyl Benzoate with Pinacol Borane Catalyzed by Diethylzinc

[0069] Step 1: Under the protection of nitrogen in a glove box, benzyl benzoate (1 mmol) and pinacol borane (2.1 mmol) were mixed in a 10 mL reaction flask, and then 0.05 mL (5 mmol%) of 1 mol / L diethylzinc was added by syringe;

[0070] Step 2: The resulting mixed system was heated in an oil bath at 60 °C for 12 h, and then the reaction was terminated by exposure to air to obtain a borate compound. The product was dissolved in CDCl3, sampled, and subjected to 1 1H NMR and 13 13C NMR spectrum tests. The NMR data of the obtained product are as follows:

[0071] 1 1H NMR (400 MHz, CDCl3) δ 7.28 - 7.14 (m, 5H, Ar-H), 4.84 (s, 2H, PhCH2OBpin), 1.17 (s, 12H, BOCMe2).

[0072] 13 13C NMR (101 MHz, CDCl3) δ 138.20, 127.24, 126.32, 125.69, 81.91, 65.64, 23.57.

[0073] The calculated yield of the product 1 1H-NMR was 95%.

[0074] Example 12

[0075] Reaction of Phenyl Benzoate with Pinacol Borane Catalyzed by Diethylzinc

[0076] Step 1: Under the protection of nitrogen in a glove box, phenyl benzoate (1 mmol) and pinacol borane (2.1 mmol) were mixed in a 10 mL reaction flask, and then 0.05 mL (5 mmol%) of 1 mol / L diethylzinc was added by syringe;

[0077] Step 2: The resulting mixed system was heated in an oil bath at 60 °C for 12 h, and then the reaction was terminated by exposure to air to obtain a borate compound. The product was dissolved in CDCl3, sampled, and subjected to 1 1H NMR and 13 13C NMR spectrum tests. The NMR data of the obtained product are as follows:

[0078] 11H NMR (400 MHz, CDCl3) δ 7.28 - 7.12 (m, 7H, Ar-H), 7.00 (d, J = 8.7 Hz, 2H, Ar-H), 6.95 (d, J = 7.4 Hz, 1H, Ar-H), 4.84 (s, 2H, PhCH2OBpin), 1.20 (d, J = 20.9 Hz, 24H, BOCMe2).

[0079] 13 13C NMR (101 MHz, CDCl3) δ 152.44, 138.20, 128.26, 127.25, 126.35, 125.71, 122.04, 118.49, 82.50, 81.96, 65.68, 23.57, 23.55.

[0080] The calculated product 1 The yield of 1H-NMR is 99%.

[0081] Example 13

[0082] Reaction of phenyl formate with pinacol borane catalyzed by diethylzinc

[0083] Step 1: Under the protection of nitrogen in a glove box, phenyl formate (1 mmol) and pinacol borane (2.1 mmol) were mixed in a 10 mL reaction flask, and then 0.05 mL (5 mmol%) of 1 mol / L diethylzinc was added by syringe;

[0084] Step 2: The resulting mixed system was heated in an oil bath at 60 °C for 12 h, and then the reaction was terminated by exposure to air to obtain a borate compound. The product was dissolved in CDCl3, sampled, and subjected to 1 1H NMR and 13 13C NMR spectral tests. The NMR data of the obtained product are as follows:

[0085] 1 1H NMR (400 MHz, CDCl3) δ 7.29 (d, J = 7.8 Hz, 2H, Ar-H), 7.13 - 7.03 (m, 3H, Ar-H), 3.62 (s, 3H, MeOBpin), 1.30 (d, J = 24.7 Hz, 24H, BOCMe2).

[0086] 13 13C NMR (101 MHz, CDCl3) δ 154.97, 128.27, 122.08, 118.51, 82.56, 81.86, 51.62, 23.57, 23.49.

[0087] The calculated product 1 The yield of 1H-NMR is 99%.

[0088] Example 14

[0089] Reaction of Diethylzinc Catalyzed 4-Valerolactone with Pinacolborane

[0090] Step 1: In a nitrogen-protected glove box, 4-valerolactone (1 mmol) and pinacolborane (2.1 mmol) were mixed in a 10 mL reaction flask, and then 0.05 mL (5 mmol%) of 1 mol / L diethylzinc was added by syringe;

[0091] Step 2: The resulting mixed system was heated in an oil bath at 60 °C for 12 h, and then the reaction was terminated by exposure to air to obtain a borate compound. The product was dissolved in CDCl3, sampled, and subjected to 1 1H NMR and 13 13C NMR spectroscopic tests. The NMR data of the obtained product are as follows:

[0092] 1 1H NMR (400 MHz, CDCl3) δ 4.10 (q, J = 6.0 Hz, 1H, CH3CHOBpin), 3.76 (td, J = 6.2, 3.4 Hz, 2H, CH2), 1.56 (dd, J = 15.5, 8.7 Hz, 2H, CH2CH2OBpin), 1.48 - 1.42 (m, 2H, CH2CH2OBpin), 1.17 (d, J = 1.7 Hz, 24H, BOCMe2), 1.11 (d, J = 6.3 Hz, 3H, CH3CHOBpin).

[0093] 13 13C NMR (101 MHz, CDCl3) δ 81.59, 81.43, 69.57, 63.80, 33.14, 26.51, 23.58, 23.55, 21.55.

[0094] The calculated yield of the product 1 1H-NMR was 99%.

[0095] Example 15

[0096] Reaction of Diethylzinc Catalyzed ε-Caprolactone with Pinacolborane

[0097] Step 1: In a nitrogen-protected glove box, ε-caprolactone (1 mmol) and pinacolborane (2.1 mmol) were mixed in a 10 mL reaction flask, and then 0.05 mL (5 mmol%) of 1 mol / L diethylzinc was added by syringe;

[0098] Step 2: Heat the obtained mixed system in an oil bath at 60 °C for 12 h, and then expose it to air to terminate the reaction to obtain a borate compound. Dissolve the product in CDCl3, take samples, and perform 1 1H NMR and 13 13C NMR spectrum tests. The NMR data of the obtained product are as follows:

[0099] 1 1H NMR (400 MHz, CDCl3) δ 3.76 (t, J = 6.6 Hz, 4H, pinBOCH2CH2CH2CH2CH2CH2OBpin), 1.49 (t, J = 6.8 Hz, 4H, pinBOCH2CH2-CH2CH2CH2CH2OBpin), 1.32 - 1.25 (m, 4H, pinBOCH2CH2CH2CH2CH2CH2OBpin), 1.18 (s, 24H, BOCMe2).

[0100] 13 13C NMR (101 MHz, CDCl3) δ 81.57, 63.85, 30.40, 24.29, 23.57.

[0101] The calculated yield of the product 1 1H-NMR is 99%.

[0102] Example 16

[0103] Reaction of phthalide with pinacol borane catalyzed by diethylzinc

[0104] Step 1: In a glove box under nitrogen protection, mix phthalide (1 mmol) and pinacol borane (2.1 mmol) in a 10 mL reaction flask, and then add 0.05 mL (5 mmol%) of 1 mol / L diethylzinc using a syringe;

[0105] Step 2: Heat the obtained mixed system in an oil bath at 60 °C for 12 h, and then expose it to air to terminate the reaction to obtain a borate compound. Dissolve the product in CDCl3, take samples, and perform 1 1H NMR and 13 13C NMR spectrum tests. The NMR data of the obtained product are as follows:

[0106] 1 1H NMR (400 MHz, CDCl3) δ 7.33 (dd, J = 9.3, 4.0 Hz, 2H, Ar-H), 7.20 - 7.14 (m, 2H, Ar-H), 4.88 (s, 4H, PhCH2OBpin), 1.20 - 1.12 (m, 24H, BOCMe2).

[0107] 13 13C NMR (101 MHz, CDCl3) δ 136.47, 127.45, 127.27, 82.83, 64.06, 24.56.

[0108] The calculated product 1 The yield of 1H-NMR is 92%.

[0109] Example 17

[0110] Reaction of methyl benzoate with pinacol borane catalyzed by diethylzinc

[0111] Step 1: Under the protection of nitrogen in a glove box, methyl benzoate (1 mmol) and pinacol borane (2.1 mmol) were mixed in a 10 mL reaction flask, and then 0.05 mL (5 mmol%) of 1 mol / L diethylzinc was added by syringe;

[0112] Step 2: The obtained mixed system was heated in an oil bath at 60 °C for 12 h, and then the reaction was terminated by exposure to air to obtain a borate compound. The product was dissolved in CDCl3, sampled, and subjected to 1 1H NMR and 13 13C NMR spectrum tests. The NMR data of the obtained product are as follows:

[0113] 1 1H NMR (400 MHz, CDCl3) δ 7.25 (d, J = 4.7 Hz, 4H, Ar-H), 7.20 - 7.16 (m, 1H, Ar-H), 4.84 (s, 2H, PhCH2OBpin), 3.52 (s, 3H, MeOBpin), 1.17 (d, J = 3.6 Hz, 24H, BOCMe2).

[0114] 13 13C NMR (101 MHz, CDCl3) δ 138.24, 127.25, 126.34, 125.71, 81.93, 81.74, 65.66, 51.56, 23.58, 23.53.

[0115] The calculated product 1 The yield of 1H-NMR is 99%.

[0116] Example 18

[0117] Reaction of methyl 4-fluorobenzoate with pinacol borane catalyzed by diethylzinc

[0118] Step 1: In a nitrogen-protected glove box, methyl 4-fluorobenzoate (1 mmol) and pinacolborane (2.1 mmol) were mixed in a 10 mL reaction flask, and then 0.05 mL (5 mmol%) of 1 mol / L diethylzinc was added using a syringe;

[0119] Step 2: The resulting mixed system was heated in an oil bath at 60 °C for 12 h, and then the reaction was terminated by exposing it to air to obtain a borate compound. The product was dissolved in CDCl3, sampled, and 1 H NMR and 13 13C NMR spectra were measured. The NMR data of the obtained product are as follows:

[0120] 1 H NMR (400 MHz, CDCl3) δ 7.22 (dd, J = 9.8, 4.3 Hz, 2H, Ar-H), 6.91 (t, J = 8.7 Hz, 2H, Ar-H), 4.78 (s, 2H, PhCH2OBpin), 3.51 (s, 3H, MeOBpin), 1.16 (s, 24H, BOCMe2).

[0121] 13 13C NMR (101 MHz, CDCl3) δ 162.45, 160.01, 134.07, 114.18, 81.98, 81.71, 65.04, 51.52, 23.78, 23.58.

[0122] The calculated 1 H-NMR yield of the product was 99%.

[0123] Example 19

[0124] Reaction of Methyl 4-Methylbenzoate with Pinacolborane Catalyzed by Diethylzinc

[0125] Step 1: In a nitrogen-protected glove box, methyl 4-methylbenzoate (1 mmol) and pinacolborane (2.1 mmol) were mixed in a 10 mL reaction flask, and then 0.05 mL (5 mmol%) of 1 mol / L diethylzinc was added using a syringe;

[0126] Step 2: The resulting mixed system was heated in an oil bath at 60 °C for 12 h, and then the reaction was terminated by exposing it to air to obtain a borate compound. The product was dissolved in CDCl3, sampled, and 1 H NMR and 13 13C NMR spectra were measured. The NMR data of the obtained product are as follows:

[0127] 11H NMR (400 MHz, CDCl3) δ 7.12 (d, J = 4.4 Hz, 2H, Ar-H), 7.01 (d, J = 6.3 Hz, 2H, Ar-H), 4.77 (s, 2H, MePhCH2OBpin), 3.49 (s, 2H, MeOBpin), 2.22 (s, 3H, MePhCH2OBpin), 1.19 - 1.13 (m, 24H, BOCMe2).

[0128] 13 13C NMR (101 MHz, CDCl3) δ 135.94, 135.28, 127.92, 125.85, 81.85, 81.72, 65.57, 51.54, 23.78, 23.59, 20.08.

[0129] The calculated product 1 The yield of 1H-NMR was 98%.

[0130] Example 20

[0131] Reaction of methyl p-nitrobenzoate with pinacolborane catalyzed by diethylzinc

[0132] Step 1: Under nitrogen protection in a glove box, methyl p-nitrobenzoate (1 mmol) and pinacolborane (2.1 mmol) were mixed in a 10 mL reaction flask, and then 0.05 mL (5 mmol%) of 1 mol / L diethylzinc was added by syringe;

[0133] Step 2: The resulting mixture was heated in an oil bath at 60 °C for 12 h, and then the reaction was terminated by exposure to air to obtain a borate compound. The product was dissolved in CDCl3, sampled, and subjected to 1 1H NMR and 13 13C NMR spectral tests. The NMR data of the obtained product are as follows:

[0134] 1 1H NMR (400 MHz, CDCl3) δ 8.10 (dt, J = 8.7, 3.0 Hz, 2H, Ar-H), 7.42 (d, J = 8.8 Hz, 2H, Ar-H), 4.94 (s, 2H, NO2PhCH2OBpin), 3.51 (s, 3H, MeOBpin), 1.23 - 1.15 (m, 24H, BOCMe2).

[0135] 13 13C NMR (101 MHz, CDCl3) δ 146.29, 145.66, 125.89, 122.55, 82.34, 81.71, 64.55, 51.52, 23.58, 23.53.

[0136] Calculated product 1 The H-NMR yield is 99%.

Claims

1. A method for preparing an organoborate compound catalyzed by diethylzinc, characterized in that It includes the following steps: Step 1: Under an inert atmosphere, mix an ester compound with a borohydride compound, and then add diethylzinc. The borohydride compound is pinacol borane, and the ester compound is one of ethyl acetate, cyclohexyl acetate, isobutyl isobutyrate, methyl methacrylate, benzyl benzoate, phenyl formate, phenyl benzoate, methyl benzoate, phthalide, methyl p-toluate, methyl p-fluorobenzoate, methyl p-nitrobenzoate, 4-valerolactone or ε-caprolactone. Step 2: React the reaction system at 60-80 °C for 8-12 h, and then expose it to air to terminate the reaction to obtain the borate ester compound. The molar amount of diethylzinc is 3-5% of the molar amount of the ester compound.

2. The preparation method of the organoborate compound according to claim 1, characterized in that: The inert atmosphere in Step 1 is nitrogen.

3. The preparation method of the organic borate compound according to claim 1, wherein: The molar ratio of the ester compound to the borohydride compound is 1:(2-2.2).

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