Intramolecular dipolar cycloaddition reaction of 5H,7H-thiazolo[3,4-c]oxazol-4-ium-1-olates: synthesis of chiral 1H-pyrrolo[1,2-c]thiazole derivatives

(2R,3R)-N-Acyl-2-phenylthiazolidine-4-carboxylic acids were used to generat e SH,7H-thiazolo[3,3-c]oxazol-4-ium-1-olates with internal dipolarophiles. The intramolecular 1,3-dipolar cycloaddition of these mesoionic species led to the synthesis of new 1H-pyrrolo [1,2-c]thiazole derivatives (8a, 8b and 12) as single enantiomers. The structure of 8a was determined by X-ray cry stallography.