DFT-Guided Mechanistic Insights into Chemodivergence: A Mixed Explicit–Implicit Solvent Description to Dictate the Chemoselectivity

Herein we report a density functional theory (DFT)-guided
mechanistic
investigation of the nitrile reduction reaction, which exhibits a
solvent-dependent chemodivergence. This study reveals an interesting
mechanistic picture, highlighting the exact role of a protic solvent,
isopropanol, in regulating the reaction outcome. The explicit solvent
effect involving polar protic isopropanol favors imine metathesis
by proton hopping through stepwise addition and elimination steps
and thus produces a secondary amine as the final product. In contrast,
the nonpolar solvent n-hexane is incapable of facilitating
the proton migration and stops the solvent-assisted imine metathesis.
As a result, only primary amines are obtained as the final product.
This DFT study provides a recipe for the choice of solvents that can
dictate chemoselectivity in product formation.