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

Mahiro Sakuraba; Taichi Morishita; Taiki Hashimoto; Sensuke Ogoshi; Yoichi Hoshimoto

doi:10.1055/a-2110-5359

Synlett, Table of Contents

Synlett 2023; 34(18): 2187-2192
DOI: 10.1055/a-2110-5359

cluster

Modern Boron Chemistry: 60 Years of the Matteson Reaction

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

Mahiro Sakuraba

^aDepartment of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan

,

Taichi Morishita

^aDepartment of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan

,

Taiki Hashimoto

^aDepartment of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan

,

Sensuke Ogoshi∗

^aDepartment of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan

,

Yoichi Hoshimoto ∗

^aDepartment of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan

^bCenter for Future Innovation (CFi), Division of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan

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Abstract

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Abstract

A 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.

Key words

triarylboranes - Lewis acids - frustrated Lewis pairs - hydrogenation - boron catalysis - hydrogen separation

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References

References and Notes

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