Hefei National Research Center for Physical Sciences at the Microscale and Department of Chemistry, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China.
State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, Gansu, 730000, P. R. China.
Angew Chem Int Ed Engl. 2023 Jun 19;62(25):e202304321. doi: 10.1002/anie.202304321. Epub 2023 May 11.
Simultaneous electrochemical ring contraction and expansion reactions remain unexplored to date. Herein, the reductive electrosynthesis of heterocycle-fused fulleroids from fullerotetrahydropyridazines and electrophiles in the presence of a trace amount of oxygen has been achieved with concurrent ring contraction and ring expansion. When trifluoroacetic acid and alkyl bromides are employed as electrophiles, heterocycle-fused fulleroids with a 1,1,2,6-configuration are regioselectively formed. In contrast, heterocycle-fused fulleroids with a 1,1,4,6-configuration are regioselectively produced as two separable stereoisomers if phthaloyl chloride is used as the electrophile. The reaction proceeds through multiple steps of electroreduction, heterocycle ring-opening, oxygen oxidation, heterocycle contraction, fullerene cage expansion, and nucleophilic addition. The structures of these fulleroids have been determined by spectroscopic data and single-crystal X-ray diffraction analyses. The observed high regioselectivities have been rationalized by theoretical calculations. Representative fulleroids have been applied in organic solar cells as the third component and exhibit good performance.
迄今为止，电化学同时环收缩和扩张反应仍未被探索。在此，在痕量氧气存在下，通过同时的环收缩和环扩张，实现了富勒四氢吡啶嗪与亲电试剂在还原条件下的杂环稠合富勒烯的电合成。当三氟乙酸和烷基溴化物作为亲电试剂时，富勒烯稠合杂环以 1,1,2,6-构型区域选择性形成。相比之下，如果使用邻苯二甲酰氯作为亲电试剂，则以两种可分离的立体异构体形式区域选择性地生成富勒烯稠合杂环，具有 1,1,4,6-构型。该反应通过多步电还原、杂环开环、氧气氧化、杂环收缩、富勒烯笼扩张和亲核加成进行。这些富勒烯的结构通过光谱数据和单晶 X 射线衍射分析确定。通过理论计算对观察到的高区域选择性进行了合理化。代表性的富勒烯已被应用于有机太阳能电池作为第三组分，并表现出良好的性能。
