A computational study on the reaction mechanism and energetics of Markovnikov and anti-Markovnikov addition in alkyne hydrothiolation reactions

The present work provides a deep insight into the mechanistic and energetic aspects of alkyne hydrothiolation reaction. This work can be regarded as the first ever computational attempt to unravel the reaction pathway under transition metal free conditions. The results confirmed a concerted pathway for uncatalyzed gas phase reactions. Reduced natural charge analysis pointed out that the characterized transition structures could be envisaged as a hypothetical ion pair, the stabilization of which led to reduced energy barriers. Hydroxyl radical catalyzed pathway was unraveled for the reaction which was then compared with the uncatalyzed reactions in terms of energy barrier and the feasibility of the mode of addition. The catalyzed reaction was also marked for its high degree of regioselectivity, leading to an unselective mixture of (E/Z) anti-Markovnikov products. (C) 2016 Elsevier B.V. All rights reserved.