SCHEDULED MAINTENANCE
Merging dual photoredox/cobalt catalysis and boronic acid (derivatives) activation for the Minisci reaction†
a
Prabhat
Ranjan,
b
Gerardo M.
Ojeda-Carralero,
ad
Javier E.
Alfonso-Ramos,
e
Erik V.
Van der Eycken
ac
and
Upendra K.
Sharma
*a
Abstract
The merger of photoredox catalysis and organometallic chemistry has effectively enabled multiple cross-coupling pathways. Here we report a visible-light promoted photoredox-cobalt catalyzed Minisci reaction of N-heteroarenes under mild 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−1 in flow vs. 0.02 mmol·h−1 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.
- This article is part of the themed collection: FOCUS: Frontiers in Boron Chemistry
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