Highly selective carbamation of aliphatic diamines under mild conditions using Sc(OTf)3 as catalyst and dimethyl carbonate as a phosgene substitute

Sc(OTf)(3) is an effective catalyst for bis-carbomethoxylation of aliphatic diamines with dimethyl carbonate (DMC) under very mild conditions. At ambient temperature (293 K), in the presence of Sc(OTF)(3), aliphatic diamines, such as 1,6-diaminohexane (1), 1,4-diaminobutane (2), 1,3-diaminopropane (3), meta-xylylenediamine (4) and para-xylylenediamine (5), react with DMC to afford the corresponding dicarbamates in high yields. The carbomethoxylation reaction is highly selective (approximate to 100%). Under the used working conditions, side-reactions, such as formation of ureas and/or N-methyl derivatives, are repressed. The starting catalyst, Sc(OTF)(3), modifies during the catalytic process and converts into Sc-methoxo species by losing OTf groups, as the isolation of unprecedented mono-urethane triflic salts, (MeO(O)CNH-R-NH3)O3SCF3 (R = -(CH2)(6-), meta-C6H4(CH2)(2-)), also indicates. The modified catalyst can be recovered at the end of the reaction and recycled. (c) 2006 Elsevier B.V. All rights reserved.