Studies on Organophosphorus Compounds XVI On O,O‐Dialkyl Dithiophosphoric Acids and N, N, N′, N′‐Tetramethylthiophosphoric Diamide as Thiation Agents: Conversion of Carboxamides into Thiocarboxamides, Alkyl Dithiocarboxylates, or Nitriles

Abstract

AbstractBy heating carboxamides with O,O‐diethyl dithiophosphoric acid, 1, at 110‐125 °C the corresponding thiocarboxamides and/or ethyl dithiocarboxylates were formed. ortho‐Substituted N, N‐dimethylbenzamides only gave the corresponding thiocarboxamides. By using O,O‐dipropyl dithiophosphoric acid and O,O‐diisopropyl dithiophosphoric acid, thiocarboxamides were also prepared, and the corresponding propyl and isopropyl dithiocarboxylates were isolated after prolonged reaction time. Reactions of sec‐ and tert‐carboxamides with N, N, N,' N′‐tetramethylthiophosphoric diamide, 2, In HMPA at elevated temperatures produced the corresponding thiocarboxamides in high yields. Primary carboxamides were converted into the corresponding nitriles after heating with 2 in HMPA. Small amounts of primary thiocarboxamides were isolated in most of these reactions. Formanilide reacted with 2 in HMPA to give N, N‐dimethyl‐N′‐phenylformamidine in 95% yield.