title: Convergent Synthesis of 2H-Chromenes - a Formal [3+3] Cycloaddition by a One-pot, Three-Step Cascade.
abstract: In cases in which the palladium-catalyzed coupling of a bromoquinone with a vinyl stannane affords a vinyl quinone that enolizes, the resulting ortho-quinone methide undergoes an oxa-6π electrocyclization. Enolization is promoted by the presence of a polar additive. The net conversion is a formal [3+3] cycloaddition that gives 2H-chromenes. Because the first two steps of the cascade are catalyzed, the overall conversion is an example of multicatalysis. Yields for the optimized, one-pot protocol are dramatically improved over the conventional stepwise process.
authors.affiliation: Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794, USA.
authors.forename: Kathlyn A
authors.initials: KA
authors.lastname: Parker
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Mindt