A Convenient Deoxygenation of Sulfoxides with CO(II) and NaBH4

Abstract
Complex species, presumably transition metal hydrides, prepared from NaBH4 and transition metal salts have been used in the reduction of nitro, cyano, halo and amido functional groups.1 We recently reported that Co (II) and NaBH4 in ethanol reduced alkenes and alkynes in high yields, and that the regent displayed remarkable steric selectivity in the reduction of alkenes: mono>di>tri- and tetra-substituted alkenes.2 We now report that the same reagent could be conveniently employed for the efficient reduction of sulfoxides to sulfides. A number of conditions have previously been reported to deoxygenate sulfoxides to sulfides in varying yields: for example, SO9 3, etc.