The title triarylamine N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-3′,3′,4′,7′-tetramethyl-2′,3′-dihydrospiro[fluorene-9,1′-indene]-2-amine is a new hole transport material for organic solar cells. After investigating different discovery approaches (Schemes 1 + 2), a multi gram-scale synthetic sequence was developed (Scheme 4). The key intermediate 2-bromo-9-(2,5-dimethylphenyl)-9H-fluorene was accessible from 2-bromo-9-fluorenone by either the sequence Grignard reaction, Et₃SiH/BF₃ reduction or by direct arylation of the corresponding 2-bromo-9-fluorenol. Alkylation at C(9) of 2-bromo-9-(2,5-dimethylphenyl)-9H-fluorene with methallyl chloride and cyclization by an intramolecular Friedel-Crafts alkylation led to the key building block 2-bromo-3′,3′,4′,7′-tetramethyl-2′,3′-dihydrospiro[fluorene-9,1′-indene] (Scheme 4). A Buchwald-Hartwig coupling was employed (Scheme 3 + 4) for the assembly of the final triarylamines. The developed gram-scale synthesis of the title compound is scalable and chromatography-free with an overall yield >25 % over 5 steps.

中文翻译：

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N,N-双(9,9-二甲基-9H-芴-2-基)-3',3',4',7'-四甲基-2',3'-二氢螺环的可扩展且无色谱合成[芴-9,1′-茚]-2-胺，一种新型有机太阳能电池空穴传输材料

标题三芳胺N , N-双(9,9-二甲基-9H-芴-2-基)-3',3',4',7'-四甲基-2',3'-二氢螺[芴-9 ,1'-茚]-2-胺是一种用于有机太阳能电池的新型空穴传输材料。在研究了不同的发现方法（方案 1 + 2）后，开发了多克级合成序列（方案 4）。关键中间体2-溴-9-(2,5-二甲基苯基)-9 H-芴可以通过格氏反应、Et ₃ SiH/BF ₃还原或直接芳基化从2-溴-9-芴酮得到。相应的2-溴-9-芴醇。2-溴-9-(2,5-二甲基苯基)-9 H-芴与甲代烯丙基氯在 C(9) 处烷基化，并通过分子内Friedel-Crafts烷基化环化，得到关键结构单元 2-bromo-3'， 3',4',7'-四甲基-2',3'-二氢螺[芴-9,1'-茚]（方案4）。采用Buchwald-Hartwig偶联（方案 3 + 4）来组装最终的三芳基胺。所开发的标题化合物的克级合成是可扩展的并且无需色谱法，5个步骤的总产率>25%。