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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
C3-H Formylation of 2-Arylquinolines via Intermolecular Cyclizative Rearrangements Coupled with Selective C-C Bond
Di Tian1, Ping Pu2, Lu-Sen Yang1
1School of Pharmaceutical Sciences, Shanghai Jiao Tong University, Shanghai200240, China.
Abstract:
The direct, C3-selective formylation of azaarenes via site-specific C-H functionalization represents a step-economical strategy to upgrade simple feedstocks into structurally diverse N-heterocyclic building blocks. Despite the synthetic significance of this transformation, regioselective meta-formylation protocols for quinolines have remained largely unexplored to date. Herein, we report a practical strategy coupling intermolecular cyclizative rearrangement and selective C-C bond cleavage for the highly C3-selective formylation of 2-arylquinolines with excellent chemoselectivity. Specifically, quinoline N-oxides and dimethyl acetylenedicarboxylate (DMAD) undergo a sequential cascade process involving [3+2] heteroannulation, [3,5]-sigmatropic rearrangement, and three successive selective C-C bond cleavage events, thus affording the corresponding 3-carboxaldehyde azaarenes with high efficiency.
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