Visible Light Mediated Synthesis of 6H-Benzo[c]chromenes: Transition-Metal-Free Intramolecular Direct C-H Arylation

MICAELA D. HEREDIA; MARCELO PUIATTI; ROBERTO A. ROSSI; MARÍA E. BUDÉN

ORGANIC & BIOMOLECULAR CHEMISTRY

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2021

1477-0520

A synthetic approach towards 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 a 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 were found and induces the ET as the initial step in the photocyclization reaction. Furthermore, to explain the regiochemical outcome of this reaction, a theoretical analysis was performed with DFT methods.