Tandem C–C Bond Cleavage of ­Cyclopropanols and Oxidative Aromatization by Manganese(IV) Oxide in a Direct C–H to C–C Functionalization of Heteroaromatics
We report a direct C–H to C–C bond functionalization of electron-deficient heteroaromatics enabled by mild C–C bond cleavage of cyclopropanols as a new route to β-aryl carbonyl-containing products. Additionally, as an alternative to using a “catalyst” that requires an excess amount of a sacrificial oxidant for regeneration and/or oxidative aromatization, this paper features manganese(IV) oxide as an inexpensive “dual role” reagent – effecting both C–C bond cleavage and ultimate rearomatization. Under the specified conditions, a variety of heterocycles proved competent for regioselective C–C bond formation, alongside a diverse array of cyclopropanols with broad functional-group tolerance. We highlight applications to complex-molecule synthesis and direct derivatization of biologically active alkaloids. Furthermore, kinetic isotope effect (KIE) experiments, radical scavengers, and some insight into the application of tri- and tetravalent manganese species are invoked to shape an initial mechanistic hypothesis.