Green Synthesis of Stereodefined Tri- and Tetrasubstituted Alkenes <i>via</i> 100% Atomeconomic and Regio-, and Stereoselective Halo-chalcogenation and Sulfonylation of Alkynes

Achieving 100% atom economy in an organic transformation is a challenging task but it is always desirable in the context of green chemistry. Difunctionalization of alkynes using a bifunctional reagent is a useful strategy to achieve 100% atom economy, however, the challenge is to control the regio- and stereoselectivity of the reaction. In this article, we discuss the recent advances in developing 100% atom economic, highly regio- and stereoselective halo-chalcogenation and chlorosulfonylation strategies with alkynes for the green and sustainable synthesis of stereodefined tri- or tetrasubstituted alkenes, and its application in accessing valuable molecules including a marketed drug in a green and sustainable manner. The green chemistry metrics are presented to highlight the greenness of some of these protocols.