Issue 1, 2022

Visible light mediated synthesis of 6H-benzo[c]chromenes: transition-metal-free intramolecular direct C–H arylation

Abstract

A synthetic approach towards the 6H-benzo[c]chromene ring under visible light and transition-metal-free conditions has been developed. Benzochromenes are synthesized from the corresponding (2-halobenzyl) phenyl ethers or (2-halophenyl) benzyl ethers using KOtBu in dimethyl sulfoxide (DMSO) at room temperature (rt) and blue light-emitting diodes (LEDs) as the light source. This methodology replaces the use of ligands or additives, high temperatures and toxic solvents. The photostimulated reaction exhibits very good tolerance to different functional groups and 5H-dibenzo[c,f]chromenes are also effectively obtained. An electron donor–acceptor complex formed by the dimsyl anion and (2-halobenzyl) phenyl ethers was found and it induces the ET as the initial step in the photocyclization reaction. Furthermore, in order to explain the regiochemical outcome of this reaction, a theoretical analysis was performed using DFT methods.

Graphical abstract: Visible light mediated synthesis of 6H-benzo[c]chromenes: transition-metal-free intramolecular direct C–H arylation

Supplementary files

Article information

Article type
Paper
Submitted
25 ago. 2021
Accepted
22 nov. 2021
First published
22 nov. 2021

Org. Biomol. Chem., 2022,20, 228-239

Visible light mediated synthesis of 6H-benzo[c]chromenes: transition-metal-free intramolecular direct C–H arylation

M. D. Heredia, M. Puiatti, R. A. Rossi and M. E. Budén, Org. Biomol. Chem., 2022, 20, 228 DOI: 10.1039/D1OB01673C

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