efficient catalytic asymmetric Friedel–Crafts alkylation of indoles with alkylidene malonates has been developed by using a chiral N,N′‐dioxide–Sc(OTf)3 complex as the catalyst (see scheme). Some opticallyactive intermediates containing the indole skeleton have been synthesized, such as indolepropionic acid, tryptamines, and β‐carbolines. The coordination between the scandium atom and the chiral N,N′‐dioxide
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.