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

BUDÉN, MARÍA E.

ORGANIC & BIOMOLECULAR CHEMISTRY

ROYAL SOC CHEMISTRY

Año: 2021 vol. 20 p. 228 - 228

1477-0520

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 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 were found and 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 with DFT methods.