Synthesis of high enantiomeric purity gem-dihalocyclopropane derivatives from biotransformations of nitriles and amides
摘要:
Enantioselective biotransformations of geminally dihalogenated cyclopropanecarbonitriles and amides are described. Both the reaction rate and enantioselectivity of the nitrile hydratase and amidase involved in Rhodococcus sp. AJ270 microbial cells are strongly governed by the nature of gein-disubstituents on the cyclopropane ring; the amidase generally exhibits steric dependence on the substituents while both the steric and electronic factors of the substituents may affect the action of the nitrile hydratase. The match of steric bulkiness of the substituents at 2- with that at 3-positions on the cyclopropane ring benefits the efficient and highly enantioselective reaction. Coupled with facile chemical transformations, biocatalytic transformations of nitrile and amide supply an effective synthesis of optically active 2,2-disubstitued-3-phenylcyclopropanecarboxylic acid and amide in both enantiomeric forms. (C) 2003 Elsevier Ltd. All rights reserved.
芳基碘化物和溴化物与丙烯醛二乙缩醛在Pd(OAc)(2),(n)()Bu(4)NOAc,K(2)CO(3),KCl和DMF存在下的反应,于90直至乙缩醛消失,然后向粗制反应混合物中加入2 N HCl,可以得到高至高收率的肉桂醛。芳基卤化物中可耐受多种官能团,包括醚,醛,酮,酯,二烷基氨基,腈基和硝基。靠近氧化加成位点的取代基的存在不妨碍反应。