An unprecedented ruthenium-catalyzed direct and selective alkyne hydrochlorination is reported and leads to vinylchlorides in excellent yields with atom economy. The reaction proceeds at room temperature from terminal alkynes and provides a variety of chloroalkenes. Only the regioisomer resulting from the formal Markovnikov addition is selectively formed. Mechanistic studies show the stereoselective syn addition of HCl to alkynes at room temperature and suggest a chloro hydrido Ru(IV) species as a key intermediate of the reaction.

An efficient, novel and direct access to 1-halo-1,3-butadienes is developed. This stereoselective ruthenium-catalysed reaction proceeds under mild conditions via the head-to-head oxidative coupling of two alkynes and a concomitant hydrohalogenation.