阅读说明：本技术 脱质子苯基桥连β-酮亚胺锂化合物在硼氢化反应中的应用 (Application of deprotonated phenyl bridged beta-ketimine lithium compound in hydroboration reaction ) 是由 薛明强 徐晓娟 周帅 康子晗 洪玉标 刘倩倩 于 2020-06-16 设计创作，主要内容包括：本发明公开了脱质子苯基桥连β-酮亚胺锂化合物在硼氢化反应中的应用,所述硼氢化反应以酯、硼烷为反应底物。本发明利用首次公开的脱质子苯基桥连β-酮亚胺锂化合物催化酯和频哪醇硼烷的硼氢化反应,从而开发出一类高效的催化硼氢化反应的方法,其结构简单,合成容易,可以高活性的催化酯和硼烷的硼氢化反应,与已有的催化体系相比,降低了催化剂用量,温度较温和,并且产率较高。(The invention discloses an application of a deprotonated phenyl bridged beta-ketimine lithium compound in a hydroboration reaction, wherein ester and borane are used as reaction substrates in the hydroboration reaction. The invention utilizes the deprotonated phenyl bridged beta-ketiminate lithium compound to catalyze the hydroboration reaction of ester and pinacol borane for the first time, thereby developing a high-efficiency method for catalyzing the hydroboration reaction, which has the advantages of simple structure, easy synthesis, high activity, reduction of the catalyst dosage, mild temperature and high yield compared with the existing catalytic system, and can catalyze the hydroboration reaction of ester and borane.)

1. The application of the deprotonated phenyl bridged beta-ketimine lithium compound in the hydroboration reaction is characterized in that ester and borane are used as reaction substrates in the hydroboration reaction; the chemical structural formula of the deprotonated phenyl bridged beta-ketimine lithium compound is as follows:

。

2. the use according to claim 1, wherein the temperature of the hydroboration reaction is between room temperature and 60 ℃^oCThe time is 1.5 to 2.5 hours.

3. Use according to claim 1, wherein the borane is pinacolborane; the ester is gamma-valerolactone, methyl acetate, benzyl benzoate, methyl benzoate and methyl 4-bromobenzoate.

4. The application of claim 1, wherein a small molecule organic lithium solution and a ligand solution are mixed and then react to obtain a catalyst deprotonated phenyl bridged beta-ketiminate lithium compound; the ligand has the following chemical structural formula:

5. a method for synthesizing borate ester comprises the following steps of preparing borate ester through hydroboration reaction by taking a deprotonated phenyl bridged beta-ketimine lithium compound as a catalyst and taking ester and borane as raw materials; the chemical structural formula of the deprotonated phenyl bridged beta-ketimine lithium compound is as follows:

6. the method of synthesizing a boronic ester according to claim 5, wherein the catalyst is used in an amount of 1% of the molar amount of the ester, and the molar ratio of the borane to the ester is 2.2: 1.

Technical Field

The invention relates to a lithium compound and application thereof in the field of organic synthesis, in particular to a deprotonated beta-ketimine lithium compound, a preparation method thereof and application thereof in hydroboration reaction of ester.

Background

In recent years, the hydroboration reaction of ester has become one of the research hotspots of researchers, and more reports about the hydroboration reaction of ester mainly relate to main group metal catalysts and rare earth metal catalysts. In 2014, Sadow topic group reported a Mg complex To^MMgMe (To^M= tris (4, 4-dimethyl-2-oxazolinyl) phenylboronate) can efficiently catalyze hydroboration of esters to provide alkoxy borane products [ Mukherjee, D.; Ellern, a.; Sadow, a. D) by ester cleavage.Chem. Sci. 2014,5, 959.]. In 2017, the Nembenna topic group reported magnesium amide complexes such as Mg { N (SiMe)₃)₂}₂The catalyst can efficiently catalyze the reaction of various esters and pinacolborane [ Barman, M. K.; Baishya, A.; Nembenna, M ].Dalton Trans. 2017,46, 4152.]. In 2019, the Sadow topic group reports a rare earth complex La { C (SiHMe) containing Ln-C bonds₂)₃}₃Catalytic hydroboration reduction of esters and pinacolborane [ Patnaik, S.; Sadow, A. D.Angew. Chem.2019,131, 2527.]。

Disclosure of Invention

The invention aims to provide the application of a deprotonated phenyl bridged beta-ketimine lithium compound in hydroboration reaction, which is a novel ester hydroboration reaction method and has a good substrate application range.

In order to achieve the purpose, the invention adopts the technical scheme that:

the application of a deprotonated phenyl bridged beta-ketimine lithium compound in a hydroboration reaction, wherein ester and borane are used as reaction substrates in the hydroboration reaction.

The invention also discloses a method for synthesizing the borate, which comprises the following steps of preparing the borate through hydroboration reaction by taking the deprotonated phenyl bridged beta-ketimine lithium compound as a catalyst and taking ester and borane as raw materials.

The chemical structural formula of the deprotonated phenyl bridged beta-ketimine lithium compound is as follows:

。

in the technical scheme, the temperature of the hydroboration reaction is room temperature to 60 DEG C^oAnd C, the time is 1.5-2.5 hours, and then the reaction is stopped by contacting with air to obtain the borate with different substituent groups.

In the technical scheme, the borane is pinacol borane; the ester is gamma-valerolactone, methyl acetate, benzyl benzoate, methyl benzoate and methyl 4-bromobenzoate.

In the technical scheme, the dosage of the catalyst is 1% of the molar weight of the ester, and the molar ratio of the borane to the ester is 2.2: 1.

The preparation method of the deprotonated phenyl bridged beta-ketimine lithium compound comprises the following steps of mixing a small molecular organic lithium solution and a ligand solution, and then reacting to obtain a catalyst deprotonated phenyl bridged beta-ketimine lithium compound; the ligand has the following chemical structural formula:

。

in the invention, in the small molecule organic lithium solution, the small molecule organic lithium comprises n-butyl lithium, and the solvent is an alkyl solvent, such as hexane; in the ligand solution, the solvent is an ether solvent, such as tetrahydrofuran.

According to the invention, the molar ratio of the small molecular organic lithium to the ligand is 4: 1, and the ratio is not reported in the synthesis application of the beta-ketimine anionic ligand.

The reaction for the synthesis of boronic esters is schematically as follows:

Cat: [L^ph’Li₄(THF)₄]₂{L^ph’= C₆H₄[N(CH₃)C=CHCO=CH₂]₂}

due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:

the invention utilizes the deprotonated phenyl bridged β -ketimine lithium compound to catalyze the hydroboration reaction of ester and pinacol borane for the first time, thereby developing a high-efficiency method for catalyzing the hydroboration reaction, which has the advantages of simple structure, easy synthesis and 60-degree of purity^oUnder the condition of C, the hydroboration reaction of the high-activity catalytic ester and the borane is carried out, the dosage of the catalyst is only 1 percent of the molar weight of the ester, the reaction yield can reach more than 90 percent, and compared with the existing catalytic system, the catalyst dosage is reduced, the temperature is mild, and the yield is high.

Detailed Description

The catalyst of the invention is obtained from another invention application filed on the same day by the applicant and is named as a deprotonated beta-ketiminate lithium compound and a preparation method thereof. The deprotonated phenyl bridging-ketimine lithium compound disclosed by the invention is easy to store, can be conveniently placed in a glass bottle and placed in a conventional reagent cabinet, can be prepared in a large amount at one time, can be directly used subsequently, and is harmless to experimenters in use.

The raw materials involved in the invention are all commercial products, and under the preparation method of the invention, the specific operation steps and the test purification method are conventional methods in the field; the reactions of the synthesis examples were all carried out in air.

Synthesis example

M-phenyl bridged β -ketimine ligands (L)^phH₂) Synthesis of (2)

150 mL of absolute ethanol, 10.8 g of m-phenylenediamine (100 mmol), 20.5 mL of acetylacetone (200 mmol) and a catalytic amount of p-toluenesulfonic acid were added to a three-necked flask, and heated under reflux for 24 hours to obtain a reddish brown liquid and a pale yellow solidThe mixture is filtered, and the solid is recrystallized by absolute ethyl alcohol to obtain 24.5 g of light yellow needle-shaped crystal, the yield is 90 percent and is ligand L^phH₂。¹H NMR(400 MHz, CDCl₃)：12.47 (2H, s, NH)，7.32-7.27 (1H, m, ArH), 6.94-6.91 (2H, m,ArH), 6.86 (1H, s, ArH), 5.21 (2H, s, CH=C(CH₃)N)，2.10 (6H, s, CH₃)，2.01 (6H,s, CH₃)。¹³C NMR (101 MHz, CDCl₃):196.54 (COCH₃), 159.62 (C=CH), 139.63 (Ar-C), 129.71 (Ar-C), 121.45 (Ar-C), 120.43 (Ar-C), 98.20 (=CH), 29.25 (CH₃),19.94 (CH₃)。HRMS (ESI-MS) calcd. for C₁₆H₂₀N₂O₂[M+H]⁺: 273.1558, found:273.1633。

Deprotonated phenyl bridged β -ketiminate lithium compounds [ L^ph’Li₄(THF)₄]₂Synthesis of (2)

L^phH₂+ 4n-BuLi → 1/2 [L^ph’Li₄(THF)₄]₂+ 4n-BuH ↑

A solution of n-butyllithium (19.40 mmol, 2.5M) in hexane was added to L under ice-bath conditions^phH₂(4.85mmol) in tetrahydrofuran, the solution gradually changes from light yellow clear liquid to light orange red turbid liquid, and after 1 minute of addition, the reaction is carried out for 12 hours at room temperature; after the reaction, the reaction solution was heated (100)^oC) Making it become orange red clear liquid, concentrating clear liquid until it is turbid, centrifuging, concentrating supernatant until broken crystal is generated, heating to dissolve, naturally cooling to room temperature, sealing, standing at room temperature for 1 hr, and precipitating light yellow crystal [ L^ph’Li₄(THF)₄]₂{L^ph’= C₆H₄[N(CH₃)C=CHCO=CH₂]₂Dry by conventional separation to give 2.13 g of product in 75% yield. Melting point: 194.6-196.7^oC。¹H NMR (400 MHz, C₂D₆SO)：7.60-7.13(2H, m, ArH), 7.00-6.96 (2H, m, ArH), 6.09 (2H, s), 4.55 (4H, s)，1.69-1.66(6H, m)。¹³C NMR (101 MHz, C₂D₆SO):179.53, 163.77, 154.04, 129.35, 127.83,117.68, 116.40, 95.55, 28.88, 21.95。IR (KBr): 2972.71, 2869.81, 1590.41,1500.86, 1468.03, 1412.07, 1360.89, 1318.03, 1280.73, 1238.47, 1146.11,1053.76, 1019.62, 970.28, 924.75, 887.93, 806.76, 748.66, 699.55, 643.56。

Compound [ L^ph’Li₄(THF)₄]₂：