Unraveling ligand effect on enantio- and chemoselectivity in iridium-catalyzed ether-directed C(sp³)-H borylation of cyclopropanes: A computational study

Abstract

The iridium-catalyzed ether-directed C(sp³)-H borylation of cyclopropanes represents a rare example of the borylation of the strained cycloalkanes. In this study, density functional theory calculations were conducted to elucidate the detailed reaction mechanism and the origins of the ligand-controlled enantioand chemoselectivity. The computations indicate that the reaction follows the well-established Ir(III)/Ir(V) catalytic cycle, with the hydride isomerization being the rate-and selectivity-determining step. The enantioselectivity arises primarily from the steric repulsion between the chiral ligand and the cyclopropane substrate. In addition, the bulky C5 substituent on the pyridine moiety of the chiral bidentate boryl ligand was found to promote the C(sp³)-H borylation through the π...π interaction, while suppressing the C(sp²)-H borylation via the steric hindrance.