Mechanism of C-H Alkylation of Cyclic Sulfonamides and Cyclohexylboronic Acid: A Dft Investigation

Abstract

Mechanisms for the C-H alkylation of cyclic sulfonamides have been investigated with M06-2X-D3/ma-def2-svp method and basis set in the solvent of CH3CN with SMD model. The calculations suggest that cyclohexylboronic acid goes through homolysis process to obtain the cyclohexane radical, which can have an addition reaction to get product derivates. Finally, the two possible paths (a1 and a2) could help to finish the HAT (Hydrogen Atom Transfer) process to yield final product. Gibbs free energy surfaces show that path a2 is favorable. While the addition of TFA reveals that the proton transfer process would firstly occur and the protonated cyclic aldimine  and IM2 formed a radical intermediate, which has two possible paths (b1 and b2) to yield the final product. Gibbs free energy profiles suggest that the favorable process is consecutive proton transfer and HAT reactions. All in all, the path with the participation of TFA is the most favorable.

Keywords: C-H alkylation, Cyclic sulfonamides, Cyclohexylboronic acid, DFT