Thiol-yne reaction

The thiol-yne reaction (also known as alkyne hydrothiolation) is an organic reaction between a thiol and an alkyne. The reaction product is an alkenyl sulfide. The reaction was first reported in 1949 with thioacetic acid as reagent and rediscovered in 2009. It is used in click chemistry  and in polymerization, especially with dendrimers.

This addition reaction is typically facilitated by a radical initiator or UV irradiation and proceeds through a sulfanyl radical species. With monoaddition a mixture of (E/Z)-alkenes form. The mode of addition is anti-Markovnikov. The radical intermediate can engage in secondary reactions such as cyclisation. With diaddition the 1,2-disulfide or the 1,1- dithioacetal forms. Reported catalysts for radical additions are triethylborane, indium(III) bromide and AIBN. The reaction is also reported to be catalysed by cationic rhodium and iridium complexes, by thorium and uranium complexes, by rhodium complexes,  by caesium carbonate and by gold.

Diphenyl disulfide reacts with alkynes to a 1,2-bis(phenylthio)ethylene. Reported alkynes are ynamides. A photoredox thiol-yne reaction has been reported.

Polymer chemistry
In polymer chemistry, systems have been described based on addition polymerization with 1,4-benzenedithiol and 1,4-diethynylbenzene, in the synthesis of other addition polymer systems in the synthesis of dendrimers,    in star polymers,    in graft polymerization, block copolymers, and in polymer networks. Another reported application is the synthesis of macrocycles via dithiol coupling.