title: Gold-catalyzed oxa-Povarov reactions for the synthesis of highly substituted dihydrobenzopyrans from diaryloxymethylarenes and olefins.
abstract: Oxa-Povarov reactions involving readily available diaryloxymethylarenes and aryl-substituted alkenes are reported. Their [4+2] cycloadditions were efficiently catalyzed by IPrAuSbF6 (IPr=1,3-bis(diisopropylphenyl)imidazol-2-ylidene) with high diastereoselectivity. Product analysis revealed that the reactions likely proceed by a stepwise ionic mechanism, because both E- and Z-configured β-methylstyrene gave the same cycloadducts in the same proportions.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu, 30013 (Taiwan), Fax: (+886) 3-5711082.
authors.forename: Vinayak Vishnu
authors.initials: VV
authors.lastname: Pagar
authors.forename: Chang-Chin
authors.initials: CC
authors.lastname: Tseng
authors.forename: Rai-Shung
authors.initials: RS
authors.lastname: Liu
keywords: cycloaddition; diastereoselectivity; gold; oxygen heterocycles; synthetic methods