Issue 17, 2019

Photoinitiated carbonyl-metathesis: deoxygenative reductive olefination of aromatic aldehydes via photoredox catalysis

Abstract

Carbonyl–carbonyl olefination, known as McMurry reaction, represents a powerful strategy for the construction of olefins. However, catalytic variants that directly couple two carbonyl groups in a single reaction are less explored. Here, we report a photoredox-catalysis that uses B2pin2 as terminal reductant and oxygen trap allowing for deoxygenative olefination of aromatic aldehydes under mild conditions. This strategy provides access to a diverse range of symmetrical and unsymmetrical alkenes with moderate to high yield (up to 83%) and functional-group tolerance. To follow the reaction pathway, a series of experiments were conducted including radical inhibition, deuterium labelling, fluorescence quenching and cyclic voltammetry. Furthermore, NMR studies and DFT calculations were combined to detect and analyze three active intermediates: a cyclic three-membered anionic species, an α-oxyboryl carbanion and a 1,1-benzyldiboronate ester. Based on these results, we propose a mechanism for the C[double bond, length as m-dash]C bond generation involving a sequential radical borylation, “bora-Brook” rearrangement, B2pin2-mediated deoxygenation and a boron-Wittig process.

Graphical abstract: Photoinitiated carbonyl-metathesis: deoxygenative reductive olefination of aromatic aldehydes via photoredox catalysis

Supplementary files

Article information

Article type
Edge Article
Submitted
10 Feb 2019
Accepted
18 Mär 2019
First published
18 Mär 2019
This article is Open Access

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

Chem. Sci., 2019,10, 4580-4587

Photoinitiated carbonyl-metathesis: deoxygenative reductive olefination of aromatic aldehydes via photoredox catalysis

S. Wang, N. Lokesh, J. Hioe, R. M. Gschwind and B. König, Chem. Sci., 2019, 10, 4580 DOI: 10.1039/C9SC00711C

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