Enantioselective synthesis of dihydrocouniarins via N-heterocyclic carbene-catalyzed cycloaddition of ketenes and o-quinone methides

Abstract

Chiral N-heterocyclic carbenes were found to be efficient catalysts for the formal [4. + 2] cycloaddition reaction of alky(aryl)ketenes and o-quinone methides to give the corresponding 3,3,4-trisubstituted 3,4-dihydrocoumarins in good yields with good diastereoselectivities and excellent enan- tioselectivities. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.