Carbamoylimidazolium and thiocarbamoylimidazolium salts: novel reagents for the synthesis of ureas, thioureas, carbamates, thiocarbamates and amides |
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Authors: | Justyna A Grzyb Chiaki Yoshina-Ishii RStanley Brown |
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Institution: | a Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ont., Canada M5S 3H6 b Department of Chemistry, Queen's University, Kingston, Ont., Canada K7L 3N6 |
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Abstract: | Carbamoylimidazolium salts act as efficient N,N-disubstituted carbamoylating 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. |
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Keywords: | Carbamoylimidazolium salts Thiocarbamoylimidazolium salts Ureas Thioureas Carbamates Thiocarbamates Amides |
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