The Role of the Indole in Important Organocatalytic Enantioselective Friedel-Crafts Alkylation Reactions

With the development of catalytic asymmetric methodologies directed to the synthesis of biologically active molecules during the last years, organocatalysis has emerged as a powerful tool. The organocatalytic approach is complementary to transition metal-based catalysis within the field of asymmetric synthesis and several research groups have achieved great aims in this area by the first time. The enantioselective Friedel-Crafts alkylation reaction of indoles is a powerful and direct method for preparing enantiomerically pure 3- or 2-substituted indolyl compounds and a number of organocatalyzed syntheses of these indolyl substrates have been developed in recent years. Due to the abundance of indole moieties in enantiomerically pure biologically interesting natural compounds asymmetric strategies have arisen as important processes of synthesis. These important alkylation processes including the addition of indole to alpha,beta-unsaturated carbonyl compounds, nitroalkenes and imines as well as their applications will be discussed in this review.