C-H Oxidation/Michael Addition/Cyclization Cascade for Enantioselective Synthesis of Functionalized 2-Amino-4H-chromenes.

A streamlined method for the enantioselective synthesis of 2-amino-4H-chromenes from readily available 2-alkyl-substituted phenols and active methylene compounds bearing a cyano group with up to 97% ee is presented. This reaction is a cascade procedure including manganese dioxide mediated C-H oxidation for the generation of o-quinone methides and bifunctional squaramide-catalyzed Michael addition/cyclization.