- Biocatalytic Access to Piperazines from Diamines and Dicarbonyls
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Given the widespread importance of piperazines as building blocks for the production of pharmaceuticals, an efficient and selective synthesis is highly desirable. Here we show the direct synthesis of piperazines from 1,2-dicarbonyl and 1,2-diamine substrates using the R-selective imine reductase from Myxococcus stipitatus as biocatalyst. Various N- and C-substituted piperazines with high activity and excellent enantioselectivity were obtained under mild reaction conditions reaching up to 8.1 g per liter.
- Borlinghaus, Niels,Gergel, Sebastian,Nestl, Bettina M.
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p. 3727 - 3732
(2018/04/14)
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- METHOD FOR PRODUCING OPTICALLY ACTIVE 2-METHYLPIPERAZINE
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PROBLEM TO BE SOLVED: To provide a method capable of industrially obtaining an optically active 2-methylpiperazine which is easy in handling and has good properties, instead of the isolation method of an optically active 2-methylpiperazine by conventional distillation. SOLUTION: There is provided a method for producing an optically active 2-methylpiperazine by adding a solvent to a solution of an optically active 2-methylpiperazine, followed by solvent substitution and crystallization to obtain crystals of the optically active 2-methylpiperazine. SELECTED DRAWING: None COPYRIGHT: (C)2016,JPOandINPIT
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Paragraph 0046-0052
(2017/01/26)
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- A bifunctional PdVMgO solid catalyst for the one-pot selective N-monoalkylation of amines with alcohols
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It has been found that a bifunctional metal Pd/base (MgO) catalyst performs the selective monoalkylation of amines with alcohols. The reaction goes through a series of consecutive steps in a cascade mode that involves: 1) the abstraction of hydrogen from the alcohol that produces the metal hydride and the carbonyl compound; 2) condensation of the carbonyl with the amine to give an imine, and 3) hydrogenation of the imine with the surface hydrogen atoms from the metal hydride. Based on isotopic and spectroscopic studies and on the rate of each elementary step, a global reaction mechanism has been proposed. The controlling step of the process is the hydride transfer from the metal to the imine. By changing the crystallite size of the Pd, it is demonstrated that this is a structure-sensitive reaction, whereas the competing processes that lead to subproducts are not. On these bases, a highly selective catalyst has been obtained with Pd crystallite size below 2.5 nm in diameter. The high efficiency of the catalytic system has allowed us to extend the process to the one-pot synthesis of piperazines.
- Corma, Avelino,Rodenas, Tania,Sabater, Maria J.
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supporting information; experimental part
p. 254 - 260
(2010/03/26)
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