2680-85-5Relevant academic research and scientific papers
A novel synthesis of isocyanates and ureas via β-elimination of haloform
Braverman,Cherkinsky,Kedrova,Reiselman
, p. 3235 - 3238 (2007/10/03)
A novel synthesis of isocyanates via base-induced β-elimination of haloform from N-monosubstituted trihaloacetamides is described. The rate of reaction exhibits a strong dependence on the nature of the trihalomethyl group. Thus, while the reaction of tribromoacetamides proceeds at room temperature and the reaction of trichloroacetamides requires heating in polar solvents, no reaction could be observed for any of the corresponding trifluoro derivatives. This novel β-elimination of haloform from stable and readily available trihaloacetamides was applied to a 'one-pot' synthesis of ureas which avoids the use of phosgene and isolation of isocyanates.
Process for the preparation of N-aryl-N'-(mono- or di substituted)-urea derivatives
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, (2008/06/13)
The invention relates to a new method for the preparation of N-aryl-N'-(mono- or disubstituted)-urea derivatives having the general formula (I), STR1 wherein Aryl is an optionally substituted phenyl group, and R1 and R2 each stand for an optionally substituted alkyl, cycloalkyl, alkoxy or phenyl group, or R1 and R2 may form, together with the adjacent nitrogen atom, a nitrogen-containing heterocyclic group which may contain a further hetero atom, or one of R1 and R2 may also stand for hydrogen, with the proviso that if one of R1 and R2 is an optionally substituted phenyl group, the other may represent only hydrogen atom or an optionally substituted alkyl or alkoxy group, by reacting a carbamate of the general formula (II) with an amine of the general formula (III), or a carbamate of the general formula (IV) with an amine of the general formula (V), wherein R1, R2 and Aryl are as defined above and X is a lower alkoxy, phenoxy or substituted phenoxy group, in the presence of a tertiary amine catalyst. According to the invention a tertiary alkylamine containing altogether at least 6 carbon atoms and minimum one alkyl chain with at least 4 carbon atoms or a mixture of such tertiary alkylamines is applied as catalyst.
