Enantioselective Friedel-Crafts Alkylation Reaction of Indoles with alpha-Trifluoromethylated beta-Nitrostyrenes Catalyzed by Chiral BINOL Metal Phosphate

摘要

An efficient enantioselective Friedel-Crafts alkylation reaction of indoles with alpha-CF3-substituted beta-nitrostyrenes is disclosed. The key to success is the use of a chiral calcium BINOL bis(phosphate) complex as a Lewis acid catalyst. The reaction gives access to a wide variety of optically active indoles bearing trifluoromethylated all-carbon quaternary stereocenter (up to 20 examples) in high yields (up to 99%) with excellent enantioselectivities (up to 98%) under mild reaction conditions. Non activated alpha-alkyl-beta-nitrostyrenes also participated in the Friedel-Crafts alkylation reaction successfully.