Organotin-Mediated Selective Desulfurization: Tri-n-butyltin Hydride Reduction of Unsymmetric Sulfides

Article abstract of DOI:10.1021/jo00200a039

Tri-n-butyl hydride (TBTH) has been evaluated as a selective agent for the reductive cleavage of one C-S-bond in unsymmetric sulfides 1.Sulfides 1 (R<*>R¹) (where combinations of R and R¹ included primary, secondary, tertiary, benzylic, phenyl, allylic, and α-(to carbonyl) carbon bound to sulfur> were each reacted with 1 equiv of TBTH in the presence of AIBN initiator.Reduction by TBTH occurs initially at the R¹-S bond (where R¹ can form the more stable carbon radical intermediate) in sulfide 1 selectively, if not specifically, to yield hydrocarbon 4 and tributylstannyl alkyl sulfide 3.However, this specifity can be negated by an enhanced reacitivity toward reduction by TBTH which the C-S bond in 3 exhibits, producing hydrocarbon 6 and bis(tributyltin) sulfide.The degree of selectivity in desulfurization is determined by the competition between unsymmetric sulfide 1 and alkyl organotin sulfide 3 for TBTH.The reduction of secondary and primary alkyl C-S bonds in 1 is so slow as to discount the synthetic utility of trialkyltin hydride reduction for such sulfides.