Carbomethoxylating reactivity of methyl phenyl carbonate toward aromatic amines in the presence of group 3 metal (Sc, La) triflate catalysts

Methyl phenyl carbonate (MPC) has been investigated as a carbomethoxylating agent of aromatic amines in the presence of group 3 metal (Sc or La) triflate catalysts. Under mild conditions (363 K), both Sc(OTf)(3) and La(OTf)(3) (OTf = O3SCF3) can promote the carbamation of aniline and a few industrially relevant aromatic diamines, such as 4,4'-methylenedianiline (MDA) and 2,4-diaminotoluene (TDA), with MPC. Carbamate yield and selectivity are markedly affected by the experimental conditions (temperature, reaction medium, nature of the metal center). Sc(OTf)(3) is a more effective and selective carbamation catalyst than La(OTf)(3). Ad hoc experiments have shown that, in the presence of the M(OTf)(3) (M = Sc, La) catalysts, MPC is not only more reactive but also a more selective carbomethoxylating agent than dimethyl carbonate (DMC). (C) 2004 Elsevier Inc. All rights reserved.