Synthesis of the N-allylthioamide derivatives of cyclic oxo- and dioxo- acids and their cyclization to the derivatives of 4,5-dihydrothiazole

The title N-allylthioamides (1a-f) were synthesized in the reaction of ally l isothiocyanate with enamines (1a-c) and 1,3-diketones (1d-f), respectivel y carried out in an acetonitrile solution in the presence of DBU. When trea ted with the bromine-dioxane complex or with iodine, they underwent cycliza tion to the corresponding derivatives of 4,5-dihydrothiazole (2a-g). NMR sp etroscopy made it possible to elucidate the tautomeric structures of the th ioamides and thiazolines.