Selective Reduction of an Aromatic Nitro Group to an Azoxy Unit in the Presence of an Aliphatic Nitro Group

Summary. Chemoselective reduction of 1-nitro-2-(2-nitro-2-methylpropyl)-benzene to 2,2′-di-(2-nitro-2-methylpropyl)-azoxybenzene was achieved with sodium borohydride in methanol in the presence of substoichiometric amounts of bismuth, whereas reduction with zinc in hydrochloric acid gave a mixture of the latter, 1-amino-2-(2-amino-2-methylpropyl)-benzene, and 3,3-dimethyl-3,4-dihydrocinnoline, and showed poor reproducibility. The crystal structure of the azoxybenzene was determined by single-crystal X-ray diffraction. Corresponding author. E-mail: siemeling@uni-kassel.de Received August 26, 2002; accepted September 2, 2002