Pt(IV)-catalyzed generation and [4+2]-cycloaddition reactions of o-quinone methides

Novel intermolecular and intramolecular generations of ortho-quinone methides and their formal [4+2]-cycloaddition reactions with olefins catalyzed by PtCl(4) and AuCl(3) under mild conditions have been developed. Good to excellent yields (up to 99%) and diastereoselectivity (up to >99:1) of the chromans were obtained. PtCl(4) was found to be effective and compatible with various functional groups present in the substrates. A mechanism accounting for its catalytic cycle is proposed and discussed. (C) 2011 Elsevier Ltd. All rights reserved.