SELENOSULFONATION OF ALLENES

Article abstract of DOI:10.1016/S0040-4020(01)96712-2

Se-Phenyl p-tolueneselenosulfonate (1a) undergoes highly regioselective, photoinitiated freeradical addition to allenes (R₁CH=C=CR₂R₃) to afford the regioisomer R₁CH(SePh)C(SO2Ar)=CR₂R₃ (13) arising from addition to the p-tolylsulfonyl group to the central carbon of the allene and transfer of the phenylseleno group to the less highly substituted of the two terminal carbons.This regioselectivity, which contrasts with that observed in the majority of radical additions to allenes, can be explained by reference to concepts proposed by Heiba as being important in determining the orientation in different radical additions to allenes.Oxidation of the PhSe group in 13 to PhSe(O) gives allylic selenoxides that undergo a reaction sequence of facile, concerted, <2,3>-sigmatropic rearrangement followed by hydrolysis of the resulting selenenate to afford β-tolylsulfonyl-substituted allylic alcohols, R₁CH=C(SO2Ar)C(OH)R₂R₃ (14) in 70-98percent yield.Photoaddition of 1a to allenes, followed by the conversion of 13 to 14 thus provides a simple, highyield route to a wide variety of 14, a class of compounds that would seem to have a number of interesting possible uses in synthesis.