RSS-Feed abonnieren
DOI: 10.1055/s-2007-990813
Preparation of Mono-, Di-, and Trisubstituted Ureas by Carbonylation of Aliphatic Amines with S,S-Dimethyl Dithiocarbonate
Publikationsverlauf
Received
19 July 2007
Publikationsdatum:
25. September 2007 (online)
Abstract
General procedures are reported to prepare N-alkylureas, N,N′-dialkylureas (both symmetrical and unsymmetrical), and N,N,N′-trialkylureas by carbonylation of aliphatic amines, employing S,S-dimethyl dithiocarbonate (DMDTC) as a phosgene substitute. All reactions were carried out in water. Symmetrical disubstituted ureas were prepared directly working at 60 °C with a molar ratio of DMDTC:amine = 1:2, preferably under nitrogen. Unsymmetrical ureas were prepared in two steps via S-methyl N-alkylthiocarbamate intermediates, which are formed selectively in the first step at room temperature. These intermediates react in the second step with ammonia or various aliphatic amines, both primary and secondary, at temperatures varying between 50 and 70 °C. All the target ureas were obtained in high yields (28 examples, average yield 94%) and with very high purity (generally >99.2%). Also to be noted is the recovery of a co-product of industrial interest, methanethiol, in an amount of two moles for each mole of DMDTC, with complete exploitation of the reagent.
Key words
ureas - carbonylation - amines - dithiocarbonates - thiocarbamates