The carbene-like behavior of terminal phosphinidene complexes toward olefins. A new access to the phosphirane ring

Article abstract of DOI:10.1021/om00081a021

In the presence of copper(I) chloride, (7-R-7-phosphanorbornadiene)P-M(CO)₅ complexes (M = Cr, W) decompose around 55°C to give the corresponding terminal phosphinidene complexes RP=M(CO)₅. These transient phosphinidene complexes react in situ with olefins to give phosphirane complexes. The stereochemistry of the starting olefin is retained in the phosphirane ring, thus suggesting a concerted process. The reaction with 1,3-dienes yields 2-vinylphosphirane complexes that rearrange around 100°C to the corresponding phospholenes. On the contrary, the reaction with α,β-unsaturated ketones gives directly the 1,2-oxaphospholene complexes, but the formation of an intermediate 2-acylphosphirane cannot be excluded. With methyl methacrylate, the 2-(methoxycarbonyl)phosphirane is formed and is apparently stable. With ethyl vinyl ether, the 2-ethoxyphosphirane transiently obtained is so reactive that neutral water cleaves the P-C(OEt) bond of the ring to give a secondary α-phosphinoacetaldehyde that is stabilized as its P-W(CO)₅ complex. An excess of vinyl ether also reacts with the 2-ethoxyphosphirane to give a 2,4-diethoxyphospholane. In all its reactions, PhP=W(CO)₅ apparently behaves as a singlet electrophilic carbene.