The Reaction of 4-Amino-2-oxazolines with Isocyanates and Isothiocyanates. Synthesis and X-Ray Structures of Polysubstituted 2-Imidazolidinones, 1,3-Oxazolidines and 1,3-Thiazolidines.

Abstract Reactions of 4-alkylamino-2-phenyl-2-oxazolines 1 with isocyanates and isothiocyanates provide unprecedented efficient and regioselective heterocycle–heterocycle transformations. Compounds 1 reacted rapidly with tosyl isocyanate yielding directly 3-alkyl-4-benzamido-1-tosyl-2-imidazolidinones 4 in almost quantitative yields. The corresponding ureido intermediates 2 were not isolable species. However, the reactions with non-sulfonylated isocyanates or isothiocyanates were slower, leading to the expected ureido and thioureido derivatives 5, which were easily and efficiently transformed to either polysubstituted 2-imino-1,3-oxazolidine or 2-imino-1,3-thiazolidine hydrochlorides 7, res…