title: Alkyne migration in alkylidene carbenoid species: a new method of polyyne synthesis.
abstract: The synthesis of conjugated polyyne structures via a modification of the Fritsch-Buttenberg-Wiechell (FBW) rearrangement is reported. Our adaptation provides for the 1,2-migration of an alkyne in a carbene/carbenoid intermediate that is conveniently effected via lithium-halogen exchange with the appropriate dibromo-olefinic precursor. This rearrangement is quite rapidly accomplished under mild conditions (hexane solution, -78 degrees C), and the seemingly high migratory aptitude of the alkynyl moiety provides for efficient rearrangement. This, in turn, allows for multiple rearrangements in a single molecule, greatly facilitating the construction of highly unsaturated substrates. This procedure is exploited for the rapid synthesis of symmetrical and unsymmetrical 1,3,5-hexatriynes, extended polyynes, and aryl polyyne building blocks. Most significantly, many of these structures have been or would be difficult to access via more traditional transition metal catalyzed homo- or cross-coupling techniques.
authors.affiliation: Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada.
authors.forename: Sara
authors.initials: S
authors.lastname: Eisler
authors.forename: Navjot
authors.initials: N
authors.lastname: Chahal
authors.forename: Robert
authors.initials: R
authors.lastname: McDonald
authors.forename: Rik R
authors.initials: RR
authors.lastname: Tykwinski