Amination of benzene and toluene with hydroxylamine in the presence of transition metal redox catalysts

Direct amination of toluene to toluidine with hydroxylamine over CuO–V2O5/Al2O3 catalysts

“…In addition, free-radical mechanisms have been proposed for direct amination of aromatics with hydroxylamine [17,[19][20][21]24]. The present work also favors the radical mechanism.…”

“…The remaining amount of hydroxylamine in the reaction mixture was determined by its reaction with cyclohexanone to give cyclohexanone oxime [21]. The actual procedure is as follows.…”

“…This may be due to the fact that 67 vol% acetic acid exhibits good solubility for toluene and hydroxylamine [17,20] and favorable acidity for the generation of active aminating species ( • NH 2 / • NH 3 ? ) [19,21], thus giving high conversion of toluene and 91.9% selectivity for toluidines.…”

“…The conversion of toluene increased sharply from 31.9 to 65.6% as the time is increased from 1 to 4 h. However, when the time exceeded 4 h, toluene conversion increased slightly. The reason may be due to the decomposition of hydroxylamine, by either its disproportionation and/or its interaction with Cu-V species [17,19,21]. Almost no aminating agent was left in the reaction mixture at longer reaction time as shown in Table 4.…”

“…However, most of these studies were concerned with the synthesis of aniline [17][18][19][20], only a few papers have dealt with the synthesis of toluidine. For example, Kuznetsova et al [21] investigated the amination of toluene to toluidines with hydroxylamine sulfate in the presence of Na 4 PW 11 O 39 Fe(H 2 O), V 2 O 5 /SiO 2 and V 2 O 5 /TiO 2 catalysts, the yield of toluidines was only around 26% at optimal conditions. Yu et al [22] studied this reaction over vanadium-based catalysts supported on different carriers.…”