We developed a direct oxidation reaction from a methoxy group to a keto group using a mild oxidizing agent with the aid of an oxidizable fullerene pendant. By using this key reaction, we developed a fullerene derivative that is stable even at high temperatures of 400 deg-C or higher and can be used for vacuum deposition to make thin films in organic electronic devices.

A highly efficient CuBr₂ promoted one-step direct oxidation of alkoxy indano[60]fullerenes to [60]fullerene-fused ketones is showcased. It is shown that the fullerene can behave as an electron-pool controlling the electron transfer to trigger the direct oxidation of alkoxy. This electron-pool for the direct oxidation mainly involves two steps: 1) C₆₀selectively transferred single electron to Cu(II) to afford C₆₀^•+; 2) generated C₆₀^•+ attracts electron density from the neighboring C–H bond, which is the key for initiating the direct oxidation of alkoxy. Accordingly, conventional non-fullerene functionalized alkoxy groups understandably failed to undergo one-step direct oxidation. Encouragingly, compared with current synthetic protocols for fullerenyl ketones including electrochemical synthesis, organometal-catalyzed synthesis, and photochemical synthesis, the presented one-step direct oxidation of alkoxy exhibited advantages such as facile processing procedures, highly scalable yields and low cost, for the efficient production of [60]fullerene-fused ketones, which can provide an efficient synthetic strategy to match up the high synthetic demands of fullerenyl ketone materials applied in organic and perovskite solar cells.

Reference: H.-S. Lin, Y. Ma, R. Xiang, S. Manzhos, I. Jeon, S. Maruyama, Y. Matsuo, Communications Chemistry 2021, 4, 74.