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Cleavage of Ylidic Bonds in Phosphorus Ylides: Photolysis of Thiophosphoranyl-Substituted (Triphenylphosphoranylidene)methanes
Gruetzmacher, Hansjoerg
, p. 170 - 174 (2007/10/02)
The thiophosphoranyl-substituted (triphenylphosphoranylidene)methanes 1, 6a, b are cleaved photolytically (λ > 300 nm, 3d, 0 deg C) to yield triphenylphosphane and the thio-azaphosphetanes 3 and 8a, b, b', respectively.The formation of these heterocycles is explained invoking insertion of the carbenes 2 and 7a, b into the methine CH bond of one of the isopropyl groups.If 6a is irradiated for 16 h in the presence of the phosphanes P(NMe2)3, P(OMe)3 or P(nBu)3, the new ylides 9a, b, c are obtained along with small quantities of 8a.These results indicate a cleveage of the ylidic bond in 1 and 6a, b.The failure of attempted cyclopropanation reactions of olefins as well as the absence of the expected product of a 1,2-H shift, 10, in the case of the photolysis of 6b leave doubts as to the occurrence of free carbenes.
