Remote Back Strain: A Strategy for Modulating the Reactivity of Triarylboranes

Abstract

AbstractA strategy for modulating the Lewis acidity of triarylboranes is proposed based on the concept of remote back strain. Steric repulsion and noncovalent interactions, both generated between the aryl meta-substituents of triarylboranes, are found to be critical for determining the strength of the remote back strain. Applying this concept, we synthesized B[2,6-F2-3,5-(TMS)2-C6H]3 and the liquid B[2,6-F2-3,5-(allyl)2-C6H]3 and we demonstrated their superior catalytic activity for the hydrogenation of quinoline relative to B(C6F5)3 or B(2,6-F2C6H3)3. Moreover, we established the first example of the catalytic hydrogenation of quinoline by using B[2,6-F2-3,5-(allyl)2-C6H]3 in the presence of a gaseous 1:1:1 molar mixture of H2, CO, and CO2.