Thiol-yne reaction

In organic chemistry, the thiol-yne reaction (also known as alkyne hydrothiolation) is an organic reaction between a thiol (−SH) and an alkyne (−C≡CH). The reaction product is an alkenyl sulfide (−CH=CH−S−).^[1][2]

The reaction was first reported in 1949 with thioacetic acid as reagent^[3][4] and rediscovered in 2009.^[5] It is used in click chemistry^[6][7][8] and in polymerization, especially with dendrimers.

Thiol-yne reaction
Thiol-yne reaction

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.^[9][10] With diaddition the 1,2-disulfide or the 1,1- dithioacetal forms. Reported catalysts for radical additions are triethylborane,^[11] indium(III) bromide^[12] and AIBN.^[13] The reaction is also reported to be catalysed by cationic rhodium and iridium complexes,^[14] by thorium and uranium complexes,^[15] by rhodium complexes,^[16][17][18] by caesium carbonate^[19] and by gold.^[20]

Ichinose et al. thiol-yne reaction 1987
Ichinose et al. thiol-yne reaction 1987[11]

Diphenyl disulfide reacts with alkynes to a 1,2-bis(phenylthio)ethylene.^[21] Reported alkynes are ynamides.^[22] A photoredox thiol-yne reaction has been reported.^[23]

Polymer chemistry

In polymer chemistry, systems have been described based on addition polymerization with 1,4-benzenedithiol and 1,4-diethynylbenzene,^[24][25] in the synthesis of other addition polymer systems^[26] in the synthesis of dendrimers,^{[27][28][29][30]} in star polymers,^{[31][32][33][34]} in graft polymerization,^[35] block copolymers,^[36] and in polymer networks.^[5][37] Another reported application is the synthesis of macrocycles via dithiol coupling.^[38]

See also

• Click chemistry
• Michael addition
• Radical addition
• Thiol-ene reaction