title: Development of a formal [4 + 1] cycloaddition: Pd(OAc)2-catalyzed intramolecular cyclopropanation of 1,3-dienyl beta-keto esters and MgI2-promoted vinylcyclopropane-cyclopentene rearrangement.
abstract: A formal [4 + 1] cycloaddition of 1,3-dienyl beta-keto esters has been developed. This two step process involves Pd(II)-catalyzed intramolecular cyclopropanation to produce vinylcyclopropanes and a subsequent mild vinylcyclopropane-cyclopentene rearrangement promoted by MgI(2). The cyclopropanation method notably requires the use of Mg(ClO(4))(2), presumably to facilitate keto-enol tautomerization, and is greatly improved by the use of copper(II) isobutyrate as co-oxidant. A range of substrates with various substitution patterns is demonstrated.
authors.affiliation: Department of Chemistry, Columbia University, New York, New York 10027, USA.
authors.forename: Rockford W
authors.initials: RW
authors.lastname: Coscia
authors.forename: Tristan H
authors.initials: TH
authors.lastname: Lambert