Transition metal-free cross-dehydrogenative coupling acylation of coumarins by the K2S2O8/Aliquat 336 catalytic system: a versatile strategy towards 4-aroylcoumarin derivatives†
Abstract
A new and efficient transition metal-free oxidative cross-dehydrogenative coupling (CDC) reaction is described for the preparation of 4-aroylcoumarin derivatives. In this protocol aldehydes have been used as acylating agents for acylation of 3-substituted coumarins through C(sp2)–C(sp2) bond formation using the K2S2O8/Aliquat 336 system as an inexpensive and environmentally friendly reagent. The reactions proceeded in acetonitrile at 80 °C for 2–3 h to afford the corresponding 4-aroylcoumarin derivatives in high yields.