Oxidative Coupling of 4-Hydroxycoumarins with Quinoxalin-2(1H)-ones Induced by Visible Light under Aerobic Conditions |
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Authors: | Loris Laze Paula Romero Prof. Dr. Irene Bosque Prof. Dr. Jose C. Gonzalez-Gomez |
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Affiliation: | Instituto de Síntesis Orgánica (ISO) and Departamento de Química Orgánica, Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain |
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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. |
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Keywords: | 4-hydroxycoumarins oxidative coupling photocatalysis quinoxalin-2(1H)-ones sustainable chemistry |
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