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Method for synthesizing Hantzsch ester

A synthesis method and technology of metal complexes, which are applied in asymmetric synthesis, organic chemistry methods, chemical instruments and methods, etc., can solve the problems of high cost, difficult synthesis, and unsolved shortcomings, and achieve fewer reaction steps, high yield effect

Inactive Publication Date: 2014-05-07
DALIAN INST OF CHEM PHYSICS CHINESE ACAD OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] However, there are still some deficiencies in the current research, which seriously restrict the further application of this method.
The most prominent point is that the atomic utilization efficiency of the reaction is low (<1%), only two hydrogen atoms can be utilized in the Hantzsch ester, and the reaction usually needs to add more than one equivalent of the Hantzsch ester to obtain a better yield
On the one hand, Hantzsch esters are not easy to synthesize, and the cost is high; on the other hand, the separation problem caused by the pyridine by-products generated by the oxidation of Hantzsch esters prevents biomimetic transfer hydrogenation from being applied to the production of industrial-grade products.

Method used

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  • Method for synthesizing Hantzsch ester
  • Method for synthesizing Hantzsch ester
  • Method for synthesizing Hantzsch ester

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0027] Embodiment 1: the synthesis of compound (2a)

[0028]

[0029] Pyridine 1a (50mg, 0.20mmol) and [Ru(p-cymene)I 2 ] 2 (2.0 mg, 0.002 mmol) was dissolved in ethanol. After stirring at room temperature for 10 min, the reaction system was transferred to an autoclave and filled with hydrogen (40 atm). After stirring the reaction at 50°C for 24h, the remaining hydrogen was carefully released, and column chromatography gave Hantzsch ester 2a, 49 mg of yellow solid, yield 96%, mp 160-162°C, 1 H NMR (400MHz, CDCl 3)δ5.25(s, 1H), 4.16(q, J=7.1Hz, 4H), 3.25(s, 2H), 2.18(s, 6H), 1.27(t, J=7.1Hz, 6H). 13 C NMR (100MHz, CDCl 3 )δ168.1, 144.8, 99.5, 59.7, 24.8, 19.2, 14.5.

Embodiment 2

[0030] Embodiment 2: the synthesis of compound (2b)

[0031]

[0032] Pyridine 1b (60mg, 0.20mmol) and [Rh(COD)Cl 2 ] 2 (0.9 mg, 0.002 mmol) was dissolved in ethanol. After stirring at room temperature for 10 min, the reaction system was transferred to an autoclave and filled with hydrogen (40 atm). After stirring the reaction at 50°C for 24h, the remaining hydrogen was carefully released, and column chromatography gave Hantzsch ester 2b, 58 mg of yellow solid, yield 97%, mp 196-198°C, 1 H NMR (400MHz, DMSO-d6) 8.87(s, 1H), 7.09-7.45(m, 5H), 4.89(s, 1H), 3.54(s, 6H), 2.28(s, 6H), 13 C NMR (100MHz, DMSO-d6): 168.6, 148.3, 146.1, 129.7, 128.4, 127.3, 127.3, 101.2, 51.10, 37.3, 18.5.

Embodiment 3

[0033] Embodiment 3: The in situ regeneration of compound (2a) is applied to asymmetric transfer hydrogenation

[0034]

[0035] Pyridine compound 3a (40mg, 0.20mmol), 1a (5mg, 0.02mmol), [Ru(p-cymene)I 2 ] 2 (2.4mg, 0.0025mmol) and chiral phosphoric acid (S)-5 (1.4mg, 0.002mmol) were dissolved in the mixed solvent THF / CH 2 Cl 2 (v / v, 1 / 3, 2 mL). After stirring at room temperature for 10 min, the reaction system was transferred to an autoclave and filled with hydrogen (70 atm). After stirring and reacting at 50°C for 48h, the remaining hydrogen was carefully released. Column chromatography gave compound 4a, 42 mg of white solid, with a yield of 93%, mp 115-116°C, 93% yield, 98% ee, [α] 20 D =+98.6 (c 0.84, CHCl 3 ), R f =0.30(petroleum ether / EtOAc 10 / 1). 1 H NMR (400MHz, CDCl 3 ): δ7.36-7.43(m, 5H), 7.01-7.07(m, 2H), 6.81-6.90(m, 2H), 5.08(d, J=1.7Hz, 1H), 4.23(s, 1H). ; 13 C NMR (100MHz, CDCl 3 ): δ165.4, 141.1, 136.5, 132.6, 129.2, 127.7, 125.4, 120.5, 117.1, ...

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Abstract

A method for synthesizing Hantzsch ester comprises enabling transition metal [Ru (II) and Rh (I)] to serve as a catalyst to achieve catalytic hydrogenation of Hantzsch pyridine to synthesize the Hantzsch ester. Besides, in-situ regeneration of the Hantzsch ester is applied to asymmetric transfer hydrogenation of imine, and dosage of the Hantzsch ester is reduced from original chemical equivalent to a catalytic amount.

Description

technical field [0001] The present invention relates to a method for synthesizing Hantzsch esters. Background technique [0002] The good prospect of Hantzsch ester as a hydrogen source in asymmetric biomimetic transfer hydrogenation has attracted widespread attention, and the research on this method has achieved remarkable results in just a few years. (Document 1. (a) You, S.L.Chem.Asian J.2007, 2, 820. (b) Ouellet, S.G.; Walji, A.M.; Macmillan, D.W.C.Acc.Chem.Res.2007, 40, 1327.(c) Connon, S.J.Org.Biomol.Chem.2007, 5, 3407.(d) Wang, C.; Wu, X.F.; Xiao, J.L.Chem.Asian J.2008, 3, 1750.(e) Rueping, M.; Sugiono , E.; Schoepke, F.R.Synlett 2010, 852.) List from the Max Planck Institute for Coal Research in Germany, MacMillan from Princeton University in the United States, Rueping from RWTH Aachen University in Germany, You Shuli from Shanghai Organic Institute, Du Daming from Peking University and China Science and Technology Co., Ltd. Research groups such as Gong Liuzhu from...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07D211/90C07D265/36C07B35/02C07B53/00
Inventor 周永贵陈庆安陈木旺时磊段英余长斌
Owner DALIAN INST OF CHEM PHYSICS CHINESE ACAD OF SCI
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