期刊
CHEMISTRY-AN ASIAN JOURNAL
卷 9, 期 10, 页码 2995-3004出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/asia.201402625
关键词
amides; aromatic substitution; bond cleavage; carbamates; isocyanate cations
资金
- JSPS
- University of Tokyo
- Grants-in-Aid for Scientific Research [26104508, 25460009, 13J10840] Funding Source: KAKEN
Carbamates have been used as precursors of isocyanates, but heating in the presence of strong acids is required because cleavage of the CO bond in carbamates is energy-demanding even in acid media. Direct amidation of aromatic compounds by isocyanate cations generated at room temperature from carbamoyl salicylates in trifluoromethanesulfonic acid (TfOH) was examined. Carbamates with ortho-salicylate as an ether group (carbamoyl salicylates) showed dramatically accelerated OC bond dissociation in TfOH, which resulted in facile generation of the isocyanate cation. These chemoselective intermolecular aromatic amidation reactions proceeded even at room temperature and showed good compatibility with other electrophilic functionalities and high discrimination between N-monosubstituted carbamate and N,N-disubstituted carbamate. The reaction rates of secondary and tertiary amide formation were markedly different, and this difference was utilized to achieve successive (tandem) amidation reactions of molecules with an N-monosubstituted carbamate and an N,N-disubstituted carbamate with two kinds of aromatic compounds.
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