Wang S, Lokesh N, Hioe J, Gschwind RM, König B. Photoinitiated carbonyl-metathesis: deoxygenative reductive olefination of aromatic aldehydes
via photoredox catalysis.
Chem Sci 2019;
10:4580-4587. [PMID:
31123568 PMCID:
PMC6492636 DOI:
10.1039/c9sc00711c]
[Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Accepted: 03/18/2019] [Indexed: 01/01/2023] Open
Abstract
Carbonyl–carbonyl olefination, known as McMurry reaction, represents a powerful strategy for the construction of olefins.
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
Created by potrace 1.16, written by Peter Selinger 2001-2019
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C bond generation involving a sequential radical borylation, “bora-Brook” rearrangement, B2pin2-mediated deoxygenation and a boron-Wittig process.
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