N,N′-Dioxide–scandium(III) complex catalyzed highly enantioselective Friedel–Crafts alkylation of indole to alkylidene malonates
作者:Yanling Liu、Xin Zhou、Deju Shang、Xiaohua Liu、Xiaoming Feng
DOI:10.1016/j.tet.2009.12.032
日期:2010.2
A highly efficient enantioselective Friedel-Crafts alkylation of indoles with alkylidene malonates has been developed using chiral N,N'-dioxide LA-scandium(III) complex as the catalyst, giving the corresponding products in high yields with excellent enantioselectivities (up to 99% yield and 95% ee). The product 3a was facilely converted into several interesting compounds, such as tryptamines, indolepropionic acids and beta-carbolines. It is noteworthy that the seven-membered beta-carboline-like compound has been synthesized for the first time. Based on the crystal structure of the chiral N,N'-dioxide L10-scandium(III) complex, the proposed transition state and possible catalytic cycle were presented to elucidate the reaction mechanism. (C) 2009 Elsevier Ltd. All rights reserved.