Lewis acid catalyzed Markovnikov hydrobromination and hydrochlorination of alkynes using TMSX (X = Br, Cl)

Abstract

Markovnikov hydrobromination and hydrochlorination of alkynes were achieved using TMSX (X = Br, Cl) instead of corrosive HX (X = Br, Cl) as the bromination and chlorination reagents. Mn(OAc)₂·4H₂O was used as the hydrobromination catalyst for electron-neutral/rich alkynes. For the hydrobromination of electron-deficient alkynes and hydrochlorination of alkynes, Zn(OAc)₂·2H₂O was employed as the catalyst. Mechanistic studies suggested that the in situ formed TMS-substituted alkyne might be a reactive intermediate and the proton of the terminal alkyne should be a hydrogen source for the hydrohalogenation reaction.