Unsymmetrical Dipolar Regulation of Tetrazine Cycloaddition to C60: Modulating the Reactivity and Switching Site
Zi-Zheng Liu1, Xiao-Hui Wen1, Hong-Chang Fan1
1Department of Chemistry, College of Chemistry & Chemical Engineering, Anhui University, Hefei, Anhui 230601, China.
Abstract:
Herein, we report that 1,4-unsymmetric modification of the fullerene core can tune the site selectivity and reactivity of C60. An unconventional hydrated 4,5-dihydropyridazine ring structure was formed due to the site-selective 1,2,4,5-tetrazine cycloaddition of 1,4-unsymmetrical C60 adducts. Indole substituents on C60 have been found to create a shielding effect on the nearby [6,6] double bond, influencing its reactivity toward 1,2,4,5-tetrazine cycloaddition. Furthermore, we found that by varying the 1,4-unsymmetrical bifunctionalization, bifunctional sheltering-activation tuning could be reversed, allowing site selectivity to be modulated across different hemispheres of the fullerene. 1,4-Unsymmetric C60 adducts have been demonstrated as a significant platform for the discovery and site-selective preparation of multiadducts that are rare and challenging to synthesize.
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