Alternative Sm(II) Species-Mediated Cascade Coupling/Cyclization for the Synthesis of Oxobicyclo[3.1.0]hexane-1-ols

The allylSmBr/HMPA/MsOH system has been found to be an efficient reagent for the ester-alkene coupling/cyclization cascade of readily available a-allyloxy esters. Oxobicyclo[3.1.0]hexane-1-ols were thus prepared in good to excellent yields and diastereoselectivities. Investigation on the mechanism suggested the possible existence of a new Sm(II) species, namely, CH3SO3SmBr, which resulted from the reaction between allylSmBr and MsOH and may be the actual SET reagent.