Enhanced reactivity of Li+@C60 toward thermal [2 + 2] cycloaddition by encapsulated Li+ Lewis acid

Beilstein J Org Chem. 2024 Mar 25:20:653-660. doi: 10.3762/bjoc.20.58. eCollection 2024.

Abstract

Lithium ion-endohedral fullerene (Li+@C60), a member of the burgeoning family of ion-endohedral fullerenes, holds substantial promise for diverse applications owing to its distinctive ionic properties. Despite the high demand for precise property tuning through chemical modification, there have been only a few reports detailing synthetic protocols for the derivatization of this novel material. In this study, we report the synthesis of Li+@C60 derivatives via the thermal [2 + 2] cycloaddition reaction of styrene derivatives, achieving significantly higher yields of monofunctionalized Li+@C60 compared to previously reported reactions. Furthermore, by combining experimental and theoretical approaches, we clarified the range of applicable substrates for the thermal [2 + 2] cycloaddition of Li+@C60, highlighting the expanded scope of this straightforward and selective functionalization method.

Keywords: Lewis acid catalyst; electron transfer; fullerene; ion-endohedral fullerene; thermal [2 + 2] cycloaddition.

Grants and funding

This work was partly supported by Grants-in-Aid for Scientific Research (21H01737 to H. U.) from JSPS, Japan, and financial supports from Fukamatsugumi Co., Ltd., Sendai, Japan (to Endowed Research Laboratory of Dimensional Integrated Nanomaterials, Graduate school of Science, Tohoku University).