Transfer hydrogenation of nitro compounds with heteropolyacid catalysts

12-Molybdophosphoric acid-catalyzed transfer hydrogenation of nitroaromatics in homogeneous phase under mild conditions with hydrazine as hydrogen donor is described. Lower yields were observed with ortho- and meta-substituted than with para-substituted nitrobenzenes. IR, ESR, NMR, and X-ray photoelectron studies indicated that Mo6+ is reduced to Mo5+, which is the active species, and coordinates with the electron-deficient nitro compound; in the process Mo5+ is reoxidized. (C) 1997 Academic Press.