Laze, Loris, Romero, Paula, Bosque, Irene, Gonzalez-Gomez, Jose C.
Oxidative Coupling of 4-Hydroxycoumarins with Quinoxalin-2(1H)-ones Induced by Visible Light under Aerobic Conditions
European Journal of Organic Chemistry. 2023, 26(6): e202201484. https://doi.org/10.1002/ejoc.202201484
URI: http://hdl.handle.net/10045/130932
DOI: 10.1002/ejoc.202201484
ISSN: 1434-193X (Print)
Abstract: 
Direct and selective C(sp2)-H/C(sp2)-H cross-dehydrogenative coupling has become a promising strategy to increase molecular complexity with a high atom economy. This study describes an efficient and straightforward protocol for the regioselective C3-H/C3-H cross-coupling of 4-hydroxycoumarin derivatives with quinoxalin-2(1H)-ones, including late-stage modification of natural drugs, promoted by visible light under aerobic conditions at room temperature. With this approach, a wide range of hybrid drug-like molecules were prepared, using air as the terminal oxidant. Remarkably, the C4 OH group at the coumarin ring is essential for the reaction and has been used as a handle for diverse functionalizations of the final products. Moreover, sunlight can promote the reaction under very mild and sustainable conditions, even on a gram scale. Qualitative and semi-quantitative tools were used to demonstrate the greenness advance of this methodology over previously reported ones. Several experiments were conducted to propose a plausible mechanism for this transformation.
Keywords:Oxidative coupling, 4-hydroxycoumarins, Quinoxalin-2(1H)-ones, Sustainable chemistry, Photocatalysis
Wiley-VCH GmbH
info:eu-repo/semantics/article