Pyranylidene Carbene Complexes from 1-Lithio 1,3-Dienes and M(CO)6 (M = Cr, Mo, W): Novel Synthesis and Demetalation Reaction

This paper reports a conceptually new and concise synthetic method leading to unprecedented, fully alkyl substituted pyranylidene carbene complexes 2 from M(CO)6 (M = Cr, Mo, W) and the readily available 1-lithio-1,3-butadiene 1, bearing a leaving group, via an intramolecular trapping of metallaacylate intermediates. These carbenes have been demonstrated to have interesting and unique reactivity.