A General Procedure for Mild and Rapid Reduction of Aliphatic and Aromatic Nitro Compounds Using Ammonium Formate as a Catalytic Hydrogen Transfer Agent

Selective and rapid reductLon of nitro compounds is still area of considerable synthetic interestl, particularly when a molecule has several other reducible moieties. Numerous new reagents*-l4 have been developed for reduction of aromatic nitro compounds, however little attention has been paid to the reduction of aliphatic nitro compound&ry,S, which are traditionally reduced by high pressure catalytic hydrogenation 15,16* In the past 30 years catalytic transfer hydrogenation 17-** has demonstrated great potential value in organic and biological chemistry. Cyclohexene/Pd-C has been most widely studied. Recently, ammonium formate has been successfully employed as a catalytic hydrogen transfer agent in peptide chemistry for deprotection23-24 instead of cyclohexene. Reduction of axides and cyano groups26 to the corresponding amines and methyl group has also been reported in the recent literature. In our ongoing program, we were interested in the radioisotopic synthesis of llC-amino acids (llC-half life = 20.4 min) via nitro acid intermediates. We have thus examined several classes of chemical reducing agents for e.g. FeS04/NHAOH, Cyclohexene/Pd-C, NH%-NH%/Ra-Ni, Zn/AcOH, etc., however these systems failed to yield the amino acid. In this paper we wish to report a mild, simple, rapid and selective reduction of aliphatic and aromatic nitro compounds to the corresponding amino derivatives using ammonium formate (Scheme-I).