Mechanism of formation of chiral allyl SCF3 compounds via selenium-catalyzed sulfenofunctionalization of allylboronic acids†

The detailed reaction mechanism of diphenyl selenide-catalyzed sulfenofunctionalization of chiral α-CF₃ allylboronic acids is investigated by means of density functional theory calculations. It is demonstrated that the reaction starts with the transfer of the SCF₃ group from the (PhSO₂)₂NSCF₃ reagent to the Ph₂Se catalyst, a process that is shown to be assisted by the presence of Tf₂NH acid. After a proton transfer step, the SCF₃ group is transferred to the CC double bond of the substrate to generate a thiiranium ion. Concerted deborylative opening of the thiiranium ion yields then the final product. Several representative substrates are considered by the calculations, and the origins of the stereoselectivity of the reactions are analyzed by comparing the energies and geometries of the transition states leading to the different products.