Selective Synthesis of Non-Aromatic Five-Membered Sulfur Heterocycles from Alkynes with a Proton Acid/N-Chlorophthalimide System.

Described here is a multicomponent strategy to achieve two different regioselectivities from alkynes, isothiocyanates and H 2 O with a proton acid/N-chlorophthalimide (NCPI) system, selectively obtaining non-aromatic five-membered sulfur heterocycles: 1,3-oxathiol-2-imines/thiazol-2(3H)-one derivatives through multiple bond formations. The process features readily available starting materials, mild reaction conditions, broad substrate scope, good functional group tolerance, high regio- and chemo- selectivities, gram-scale synthesis and late-stage modifications. Mechanistic studies support that the transformation process includes a combination of H 2 O and isothiocyanate, free radical formation, carbonation and intramolecular cyclization to give the products. Furthermore, the 1,3-oxathiol-2-imine derivatives with unique fluorescence characteristics, can be served as metal ions Pd 2+ sensor with "turn-off" response, showing potential applications in environmental and biological fields.