Thiol-Ene Coupling Reaction for Functionalization of Nonactivated Alkenes: Mechanism and Mathematical Model

This article is a continuation of Polo et al. In that article, we investigated the synthesis of an aminated methyl oleate through a photoinitiated thiol-ene coupling reaction between cysteamine hydrochloride and cis methyl oleate in the presence of a photoinitiator. The present article develops a mathematical model for simulating Experiment 11 of Polo et al. The new model extends the reaction mechanism proposed by Chatgilialoglu et al. to enable generation of high molar mass by-products; and it contains 16 kinetic constants. Nine of that constants were directly adopted from literature, five other constants were estimated from reduced ad hoc experiments, and the last two constants were estimated by fitting the complete model predictions to the available measurements. The model adequately predicts the normalized ¹H-NMR areas due to vinyl protons, the final weight-average molar mass, and the final concentration of desired product. The simulation results suggest an almost constant concentration of dissolved cysteamine along the reaction, and a rapid isomerization of the cis methyl oleate reagent into the trans-isomer. The desired product is generated following an approximately zero-order kinetics. The generation of both low- and high-molar mass by-products reduces the selectivity of the reaction toward the desired product.