“Group 3 metal (Sc, La) triflates as catalysts for the carbomethoxylation of aliphatic amines with dimethylcarbonate under mild conditions”

The activity of Sc(OTf)3 and La(OTf)3 (OTf¼SO3CF3) as catalysts for the phosgene-free synthesis of carbamate esters via carbomethoxylation of aliphatic amines with dimethylcarbonate (DMC) has been investigated. In the presence of M(OTf)3 (M¼Sc, La), primary and secondary aliphatic amines easily react with dimethylcarbonate, under very mild conditions (20 8C), to afford carbamate esters with good yield and excellent selectivity (h 100%). Sc(OTf)3 is a more effective catalyst than the homologue La salt. The carbomethoxylation reaction requires as strict anhydrous conditions, as, at 20 8C, the presence of water inhibits markedly the catalytic activity of both triflate salts. Temperature influences carbamate selectivity, which is lower at higher temperature because of deleterious formation of N-methylation side-products.