Enantioselective Friedel–Crafts Alkylation of Indoles with Alkylidene Malonates Catalyzed by N,N′‐Dioxide–Scandium(III) Complexes: Asymmetric Synthesis of β‐Carbolines
1. Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064 (China), Fax: (+86)?28‐8541‐8249;2. State Key Laboratory of Oral Diseases, Sichuan University, Chengdu 610041 (China)
Abstract:
An 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 optically active 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 compound has been revealed by X‐ray structure analysis.
