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 -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.