Characteristics of methoxycarbonylation of aromatic diamine with dimethyl carbonate to dicarbamate using a zinc acetate catalyst

Abstract

The methoxycarbonylation of aromatic diamines such as 2,4-toluene diamine with dimethyl carbonate using Zn(OAc)2·2H2O as a catalyst is examined to determine the influence of reaction variables on the yields of mono- and di-carbamates. These reactions yield dimethyltoluene-2,4-dicarbamate in 98% yield over 2 h at 453 K. An induction period is observed in the reaction of aromatic amines with dimethyl carbonate, but this induction period is almost completely eliminated by pretreating the catalyst with methanol. The role of methanol is investigated based on infrared absorption measurements, and a mechanism for dimethyl carbonate activation is proposed. Observed differences between the reactivities of aromatic and aliphatic amines for methoxycarbonylation are attributed to differences in the basicities of NH2 groups in these amines.