One-pot route to new α,α-difluoroamides and α-ketoamides

New alpha,alpha-difluoroamides (4a-d, 6a-d) and (x-ketoamides (5a-d, 7a-d) result from one-pot reactions of alpha-ketoacids, RCOCO2H (R = C6H5, CH3, CH3CH2, thienyl) (1a-d) with bis(2-methoxyethyl)aminosulfur trifluoride [(CH3OCH2CH2)(2)NSF3] (2) (Deoxofluor) or diethylaminosulfur trifluoride [(CH3CH2)(2)NSF3)] (3) (DAST). Product yields depend on reaction times and the ratio of reagents used. Longer reaction times (similar to36 h) with a 1:2 ratio of alpha-ketoacids and 2 or 3 gave major yields of the alpha,alpha-difluoroamides, and shorter reaction times (similar to1 h) produced alpha-ketoamides as the major products. Reactants in a 1:1 ratio resulted in alpha-ketoamides only.