Some synthetic applications of vinylphosphane oxides

Vinylphosphane oxides have been used as Michael acceptors for the diastereoselective synthesis of anti α-functionalized-β-silylated phosphane oxides and β-stannyl-, β-phenylthio- or β-phosphanyl phosphane oxides. Although the utility of these substrates as dipolarophiles was more limited, we have obtained a mixture of 3- and 4-phosphanylpyrazoles in which the latter is the major regioisomer, by 1,3-cycloaddition with N-phenylsydnone. Moreover, vinylphosphane oxides reacted with aldehydes in the presence of LDA by a Baylis–Hillman type reaction, leading to (E)-β-hydroxyphosphane oxides, which were readily converted in allenes. It is noteworthy that the application of this methodology to silylated substrates has permitted us to synthesize an interesting and more versatile silylallene.