REACTION OF LITHIUM GALLIUM HYDRIDE WITH SELECTED ORGANIC-COMPOUNDS CONTAINING REPRESENTATIVE FUNCTIONAL-GROUPS

The approximate rates and stoichiometry of the reaction of excess lith ium gallium hydride with selected organic compounds containing represe ntative functional groups were examined under the standard conditions (diethyl ether, 0 degrees C) in order to compare its reducing characte ristics with lithium aluminum hydride and lithium borohydride previous ly reported, and enlarge the scope of its applicability as a reducing agent. Alcohols, phenol, and amines evolve hydrogen rapidly and quanti tatively. However lithium gallium hydride reacts with only one active hydrogen of primary amine. Aldehydes and ketones of diverse structure are rapidly reduced to the corresponding alcohols. Conjugated aldehyde and ketone such as cinnamaldehyde and methyl vinyl ketone are rapidly reduced to the corresponding saturated alcohols. p-Benzoquinone is ma inly reduces to hydroquinone. Caproic acid and benzoic acid liberate h ydrogen rapidly and quantitatively, but reduction proceeds slowly. The acid chlorides and esters tested are all rapidly reduced to the corre sponding alcohols. Alkyl halides and epoxides are reduced rapidly with an uptake of 1 equiv of hydride. Styrene oxide is reduced to give 1-p henylethanol quantitatively. Primary amides are reduced slowly. Benzon itrile consumes 2.0 equiv of hydride rapidly, whereas capronitrile is reduced slowly. Nitro compounds consumed 2.9 equiv of hydride, of whic h 1.9 equiv is for reduction, whereas azobenzene, and azoxybenzene are inert toward this reagent. Cyclohexanone oxime is reduced consuming 2 .0 equiv of hydride for reduction al a moderate rate. Pyridine is iner t toward this reagent. Disulfides and sulfoxides are reduced slowly, w hereas sulfide, sulfone, and sulfonate are inert under these reaction conditions. Sulfonic acid evolves 1 equiv of hydrogen instantly, but r eduction is not proceeded.