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

A multicomponent strategy to achieve two different regioselectivities from alkynes, isothiocyanates and H2O with a proton acid/N-chlorophthalimide (NCPI) system is described to selectively obtain 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 the proposal that the transformation process includes a combination of H2O and isothiocyanate, free-radical formation, carbonation and intramolecular cyclization to give the products. Furthermore, the 1,3-oxathiol-2-imine derivatives possess unique fluorescence characteristics and can be used as Pd2+ sensors with a turn-off response, demonstrating potential applications in environmental and biological fields.

Automated summary

The multicomponent strategy described in this study utilizes alkynes, isothiocyanates, and H2O to achieve two different regioselectivities, selectively obtaining non-aromatic five-membered sulfur heterocycles through multiple bond formations. This 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 potential applications in environmental and biological fields.