Highly efficient chiral copper Schiff-base catalyst for asymmetric cyclopropanation of 2,5-dimethyl-2,4-hexadiene
作者:Makoto Itagaki、Koji Hagiya、Masashi Kamitamari、Katsuhisa Masumoto、Katsuhiro Suenobu、Yohsuke Yamamoto
DOI:10.1016/j.tet.2004.06.073
日期:2004.8
A remarkable increase in catalytic activity is found for the asymmetric cyclopropanation of 2,5-dimethyl-2,4-hexadiene with diazoacetate by use of the chiral copper Schiff-base complexes, which are derived from substituted salicylaldehydes, chiral aminoalcohols, and copper acetate monohydrate. Furthermore, a combination of a chiral copper Schiff-base with a Lewis acid showed an increase in yield (up to 90%) and in enantioselectivity (up to 90% ee) for the asymmetric cyclopropanation of the diene with t-butyl diazoacetate at 20degreesC. (C) 2004 Elsevier Ltd. All rights reserved.