title: The alkynyl moiety as a donor for donor-acceptor cyclopropanes.
abstract: The first trans-selective [3 + 2]-cycloaddition of a new type of donor-acceptor cyclopropane with aldehydes is presented. 2,2-Disubstituted cyclopropanes, bearing an alkyne moiety as the sole donor entity, were transformed to highly substituted tetrahydrofurans in the presence of a catalytic amount of Ca(NTf2)2/Bu4NPF6. The protocol allows for an easy access to tetrahydrofurans bearing a versatile alkyne substituent at the quarternary 2-position under very mild reaction conditions.
authors.affiliation: Institute of Organic Chemistry, RWTH Aachen University, 52074 Aachen, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Haubenreisser
authors.forename: Peter
authors.initials: P
authors.lastname: Hensenne
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schröder
authors.forename: Meike
authors.initials: M
authors.lastname: Niggemann