Synthesis of cyclic alkenylsiloxanes by semihydrogenation: a stereospecific route to (Z)-alkenyl polyenes

Abstract

Cyclic alkenylsiloxanes were synthesized by semihydrogenation of alkynylsilanes-a reaction previously plagued by poor stereoselectivity. The silanes, which can be synthesized on multigram scale, undergo Hiyama-Denmark coupling to give (Z)-alkenyl polyene motifs found in bioactive natural products. The ring size of the silane is crucial: five-membered cyclic siloxanes also couple under fluoride-free conditions, whilst their six-membered homologues do not, enabling orthogonality within this structural motif.

Keywords: alkynes; cross-coupling; hydrogenation; natural products; silanes.