Mechanism of Formation of Chiral Allyl SCF3 Compounds via Selenium-Catalyzed Sulfenofunctionalization of Allylboronic Acids

Abstract

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 Ph2Secatalyst, a process that is shown to be assisted by the presence of Tf2NH acid. After a proton transfer step, the SCF3 groupis transferred to the C=C 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.