Merging dual photoredox/cobalt catalysis and boronic acid (derivatives) activation for the Minisci reaction

01 September 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

The merger of open-shell and closed-shell organometallic chemistry steps has enabled multiple effective cross-coupling pathways. Here we report a visible-light promoted photoredox-cobalt catalyzed Minisci reaction of N-heteroarenes under mild and sustainable conditions, employing various boronic acids and derivatives as alkyl radical precursors. This study demonstrates the prominent ability of the Co co-catalyst to promote the oxidation step of the photocatalytic cycle following a reductive quenching pathway, thus avoiding the use of stoichiometric (inorganic) oxidants. This feature enables the straightforward application of photo-flow conditions, particularly attractive for an easy scale-up and to enhance the efficiency of the reaction (throughput: 0.78 mmol/h in flow vs 0.02 mmol/h in batch) Furthermore, the process is predominantly selective towards the C2-alkylation of quinolines, and a mechanistic rationale has been provided with both experimental and DFT calculation support. The developed protocol demonstrates broad applicability for the alkylation of different N-heteroarenes under suitable homogeneous conditions for a flow-compatible Minisci reaction.

Keywords

Boronic acids
Photoredox catalysis
Flow chemistry
Cobalt catalysis
Boronic esters

Supplementary materials

Title
Description
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Title
Merging dual photoredox/cobalt catalysis and boronic acid (derivatives) activation for the Minisci reaction
Description
Supporting Information reporting methodologies, mechanistic studies and compound characterization.
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