Sodium cyanoborohydride reduction of (benzyloxycarbonyl)- and (tert-butoxycarbonyl)hydrazones

(Benzyloxycarbonyl)- and (tert-butoxycarbonyl)hydrazones are easily reduced by sodium cyanoborohydride in acidic medium. The method is an alternative to catalytic hydrogenation and allows ready access to both N-benzyloxycarbonyl and N-tert-butoxycarbonyl protected N'-alkyl- and N'-arylmethylhydrazines. The products can be isolated as the solid, stable cyanoborane adducts.