On the mechanism of the deoxygenation of secondary alcohols by the reduction of their methyl xanthates by tin hydrides

Two alternate proposals for the mechanism of reduction of xanthates by tributylstannane have been examined. Evidence has been secured that under normal reduction conditions the thiocarbonyl group is attacked reversibly. At a high enough temperature the carbon radical fragments to give eventually the reduction product. Under modified conditions, where no reducing agent (Sn-H) is present, the radical formed eliminates methylthiotributylstanne and affords the thiocarbonyloxy radical observed in the e.s.r. spectrum.