Journal
TETRAHEDRON
Volume 61, Issue 30, Pages 7153-7175Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.tet.2005.05.056
Keywords
carbamoylimidazolium salts; thiocarbamoylimidazolium salts; ureas; thioureas; carbamates; thiocarbamates; amides.
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Carbamoylimidazolium salts act as efficient N,N-disubstituted carbarnoylating reagents. These salts are readily prepared by the sequential treatment of secondary amines with N,N '-carbonyldiimidazole (CDI) and iodomethane. The carbamoylimidazolium salts are more efficient carbamoyl transfer reagents than the intermediate carbamoylimidazoles, as a result of the 'imidazolium' effect. Kinetic studies on the base promoted hydrolysis of both carbamoylimidazoles and carbamoylimidazolium salts reveal over a hundred-fold rate acceleration. The salts react with amines, thiols, phenols/alcohols, and carboxylic acids in high yields, without the need for subsequent chromatographic purification of the products, producing ureas, thiocarbamates, carbamates, and amides, respectively. Analogous thiocarbamoylimidazolium salts were also synthesized from secondary amines and N,N '-thiocarbonyldiimidazole (TCDI), followed by methylation with iodomethane. (c) 2005 Published by Elsevier Ltd.
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