Issue 15, 2018

A redox-active diborane platform performs C(sp3)–H activation and nucleophilic substitution reactions

Abstract

Organoboranes are among the most versatile and widely used reagents in synthetic chemistry. A significant further expansion of their application spectrum would be achievable if boron-containing reactive intermediates capable of inserting into C–H bonds or performing nucleophilic substitution reactions were readily available. However, current progress in the field is still hampered by a lack of universal design concepts and mechanistic understanding. Herein we report that the doubly arylene-bridged diborane(6) 1H2 and its B[double bond, length as m-dash]B-bonded formal deprotonation product Li2[1] can activate the particularly inert C(sp3)–H bonds of added H3CLi and H3CCl, respectively. The first case involves the attack of [H3C] on a Lewis-acidic boron center, whereas the second case follows a polarity-inverted pathway with nucleophilic attack of the B[double bond, length as m-dash]B double bond on H3CCl. Mechanistic details were elucidated by means of deuterium-labeled reagents, a radical clock, α,ω-dihaloalkane substrates, the experimental identification of key intermediates, and quantum-chemical calculations. It turned out that both systems, H3CLi/1H2 and H3CCl/Li2[1], ultimately funnel into the same reaction pathway, which likely proceeds past a borylene-type intermediate and requires the cooperative interaction of both boron atoms.

Graphical abstract: A redox-active diborane platform performs C(sp3)–H activation and nucleophilic substitution reactions

Supplementary files

Article information

Article type
Edge Article
Submitted
13 feb 2018
Accepted
19 mar 2018
First published
19 mar 2018
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2018,9, 3881-3891

A redox-active diborane platform performs C(sp3)–H activation and nucleophilic substitution reactions

T. Kaese, T. Trageser, H. Budy, M. Bolte, H. Lerner and M. Wagner, Chem. Sci., 2018, 9, 3881 DOI: 10.1039/C8SC00743H

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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