Enantioselective synthesis of functionalized 2-amino-4H-chromenes via the o-quinone methides generated from 2-(1-tosylalkyl)phenols

An efficient bifunctional squaramide-catalyzed Michael addition/cyclization reaction of o-quinone methides generated in situ from 2-(1-tosylalkyl)phenols with active methylene compounds bearing a cyano group has been realized to synthesize chiral 2-amino-4H-chromenes with excellent enantioselectivities and broad substrate scope. (c) 2015 Elsevier Ltd. All rights reserved.