Direct Conversion of Aliphatic Carboxamides to Alkylammonium Tosylates with benzene

Article abstract of DOI:10.1021/jo00364a010

The utility of benzene (2) as a "Hofmann reagent" has been explored.Treatment of various primary, aliphatic carboxamides (RCONH2, R = methyl, ethyl, isopropyl, tert-butyl, n-pentyl, n-heptyl, undecyl, allyl, benzyl, cyclobutyl, cyclohexyl) with 2 in acetonitrile at reflux gave the corresponding alkylammonium tosylates (RN⁺H3^-OTs) in yields ranging from 57percent to 94percent.The alkylammonium tosylates separated directly from the solvent when the reaction mixtures were kept at room temperature or below.When α-phenylacetamide was allowed to react with 2 in ethanol, ethyl benzylcarbamate (4) was obtained in 50percent yield, a result consistent with the intermediate existence of benzyl isocyanate in this reaction.A mechanism for the conversion of carboxamides by 2 to alkylammonium tosylates, involving the initial formation of N-phenyl iodonio amides and their collapse to iodobenzene and alkyl isocyanates, is proposed.The reaction of malonamide with 2 in acetonitrile followed a divergent course: 2-(tosyloxy)malonamide (3) was obtained in ca. 81percent yield (crude).