palladium-catalyzed carbonylation of coumarins involving two C–C bond formations has been developed. The C–H bond oxidative functionalization proceeds through aroylation with insertion of carbon monoxide to give arylcoumarin ketones. The reaction conditions, employing ambient pressures of CO gas as C1 feedstock, dramatically improve the generality of the carbonylation of arylhalides. A facile and efficient
Iron-catalyzed direct radical acylation of coumarins with aromatic aldehydes to regioselectively afford 3-aroyl coumarin derivatives in moderate yields was described.
cobalt-catalyzed C–H bond activation of coumarins with aryl halides or pseudohalides and carbon monoxide insertion to give various 3-aroylcoumarin derivatives is described. It is the first time that CO as C1 feedstock is used as the coupling partners in cobalt-catalyzed regioselective coumarin C–H functionalization reactions. Upon activation with manganese powder, the Co catalyzes the C–H bond activation
A transition metal-free cross-dehydrogenative coupling reaction is described for the preparation of 3-acylcoumarins. Heating a mixture of a coumarin, an aldehyde, and the K2S2O8/Aliquat 336 system in chlorobenzene at 100 degrees C for 8 h regioselectively afforded the corresponding 3-acylcoumarin derivatives in good to excellent yields. (C) 2016 Elsevier Ltd. All rights reserved.