title: Polarity matching of radical trapping: high yielding 3-exo and 4-exo cyclizations.
abstract: A catalyzed synthesis of cyclopropanes and cyclobutanes via radical chemistry is described. The method that generally proceeds in high yields uses epoxides as radical precursors and titanocene(III) complexes as the electron transfer catalysts (see scheme). The key to the success of the transformation is constituted by the chemoselectivity of radical reduction. Electrophilic enol radicals generated through cyclization are reduced rapidly whereas their precursors, nucleophilic alkyl radicals, remain unaffected.
authors.affiliation: Kekulé-Institut für Organische Chemie und Biochemie der Universität Bonn, Gerhard Domagk Strasse 1, 53121 Bonn, Germany. andreas.gansaeuer@uni-bonn.de <andreas.gansaeuer@uni-bonn.de>
authors.forename: Andreas
authors.initials: A
authors.lastname: Gansäuer
authors.forename: Thorsten
authors.initials: T
authors.lastname: Lauterbach
authors.forename: Daniel
authors.initials: D
authors.lastname: Geich-Gimbel