REDUCTION OF ORGANIC HALOGEN COMPOUNDS BY SODIUM BOROHYDRIDE

Treatment of organic halogen compounds and related derivatives with sodium borohydride in dimethyl sulfoxide or diglyme results in reduction of the carbon-halogen bond; the reactivity in dimethyl sulfoxide is somewhat greater than that in diglyme. The order of reactivity of simple haloalkanes and related derivatives is consistent with a typical SN2 displacement by borohydride on carbon, but some more complex derivatives exhibit unusual reactivity. Thus, carbon tetrachloride reacts very rapidly in aqueous diglyme or dimethyl sulfoxide to produce chloroform and dichloromethane, whereas chloroform is unreactive under the same conditions. The behavior of o-nitroiodobenzene is similar; reduction to nitrobenzene is rapid and quantitative in aqueous solvents. Substitution of deuterium oxide for the water results in almost quantitative incorporation of deuterium in the ortho position. In addition to the synthetic utility with respect to organic substrate, the reaction can be used as a convenient method for preparing solutions of diborane. © 1969, American Chemical Society. All rights reserved.