2,3-Dihydro-5H-imidazo [2,1-b][1,3]thiazin-5-one

Imidazo [2,1-b][1,3]thiazines and their fused analogues are an important class of nitrogen- and sulfur-containing heterocycles that exhibit a wide range of biological activities. Herein, a straightforward synthetic protocol for 2,3-dihydro-5H-imidazo [2,1-b][1,3]thiazin-5-one under catalyst-free, mild conditions is reported. The title compound was obtained via the regioselective heterocyclization of 4,5-dihydro-1H-imidazole-2-thiol with alkyl propiolates (methyl or ethyl) by stirring at room temperature for 24 h in ethanol. The structure of the synthesized compound and the regioselectivity of the reaction were confirmed through a combination of 1H, 13C, and 2D NMR experiments (HSQC, HMBC), LC-MS, and elemental analysis. The synthesized title compound is of interest to synthetic organic and medicinal chemistry as a starting building block with potential for further core modification.