Reduction of aromatic nitro compounds with hydrazine hydrate in the presence of an iron oxide/hydroxide catalyst. III. The selective reduction of nitro groups in aromatic azo compounds
M. Lauwiner et al., Reduction of aromatic nitro compounds with hydrazine hydrate in the presence of an iron oxide/hydroxide catalyst. III. The selective reduction of nitro groups in aromatic azo compounds, APP CATAL A, 177(1), 1999, pp. 9-14
The study on the range of applications of a cheap iron oxide/hydroxide modi
fication as a H-transfer catalyst opened up a promising new route for the s
elective reduction of nitro groups in aromatic azo compounds. A series of m
onosubstituted 3- and 4-nitrophenylazobenzenes were reduced selectively by
hydrazine hydrate in the presence of the iron oxide/hydroxide catalyst. The
selectivity for the nitro group reduction vis-a-vis that of the azo bridge
in substituted nitrophenylazobenzenes is higher for compounds with the nit
ro group in para position to the azo bridge than for the corresponding meta
counterparts. This selectivity was enhanced with stronger electron-attract
ing properties of the substituent. Moreover, the selectivity for the reduct
ion of the nitro group vis-a-vis that of the azo function can be enhanced b
y increasing the reaction temperature as the Arrhenius activation energy fo
r the nitro reduction is about twice that for the azo cleavage. (C) 1999 El
sevier Science B.V. All rights reserved.