聯苯 (8) 於鈀金屬催化系統下，藉由活化苄基sp3 C-H鍵的方式 ，環化中間的五圓環，合成茀 (10) 的結構。利用此方法已成功製備5種不同的茀衍生物，且可以應用在茚茀的合成上。此合成方法不僅提供高的產率，也有不錯的官能基容忍度及單一位向選擇性。
探討合成方法時，發現鈀金屬催化劑、鹼及溶劑在反應中均扮演關鍵的角色。此方法已調整出最佳的反應條件：將2-溴-2'-甲基聯苯 (8a) 、醋酸鈀、IPr•HCl及碳酸鉀，溶於N-甲基吡咯酮 (NMP) 中，在130-150 ºC下，反應約12小時可以得到82 %的茀 (10a)。多種不同官能基的聯苯，均能在此反應條件下，合成出相對應的茀衍生物，具有不錯的官能基容忍度，同時也有單一位向選擇性和不錯的產率。此外，對聯三苯 (11) 在相同的反應條件下，經過兩次的分子內環化，可以得到50-94 %的茚茀 (12) ，具有很高的產率，且相較於傳統的合成方法，能夠有效的縮短反應步驟，故本研究提供一個更好的合成路徑。

Several fluorene derivatives 8 have been generated by the Pd-catalyzed through the benzylic C-H bond activation, cyclization of biphenyls 10. Based on this synthetic method, five fluorene derivatives have been prepared in 81-88 %. And applied this method for prepared indenofluorene in high yield. This procedure provides not only single regioselectivity and compatibility but also excellent yield.
Systematic studies of the reaction conditions revealed that palladium catalysts, base and solvents all play key roles. The reaction conditions have been optimized. Upon heating 2-bromo-2'-methylbiphenyl (8a) in N-Methylpyrrolidone (NMP) at 130-150 ºC with a mixture of Pd(OAc)2, IPr•HCl, K2CO3, fluorene (10a) was obtained in 82 %. The several biphenyls 8 was tested under our optimized reaction condition and most of them produced the desired fluorene derivatives 10 with single regioselectivity in good yields. Our reaction condition tolerated a wide range of functional groups. Moreover, 6,12-Dihydroindeno[1,2-b]fluore-
ne (12) was synthesized from p-terphenyls 11 and it was obtained that 12 in 50-94 % yield. Compared with traditional method for preparing indenofluorene, our optimized condition provided a shorter and better synthetic route.

1 a) K. D. Belfield, S. Yao, M. V. Bondar, Adv. Polym. Sci. 2008, 213, 97 b) J. U. Wallace, S. H. Chen, Adv. Polym. Sci. 2008, 212, 145; c) A. C. Grimsdale, K. Müllen, Macromol. Rapid Commun. 2007, 28, 1676.
2 Y. Ie, Y. Umemoto, M. Nitani, Y. Aso, Pure Appl Chem. 2008, 80, 589.
3 a) O. Inganas, F. Zhang, M. R. Andersson, Acc. Chem. Res. 2009, 42, 1731; b) D. Jones, Org. Photovoltaics 2008, 57.
4 Synthesis of fluorenes: a) I. A. Kashulin, I. E. Nifant'ev, J. Org. Chem. 2004, 69, 5476; b) Y.-S. Song, S. D. Kong, S. A. Khan, B. R. Yoo, I. N. Jung, Organometallics 2001, 20, 5586; c) W. Kirmse, K. Kund, E. Ritzer, A. E. Dorigo, K. N. Houk, J. Am. Chem. Soc. 1986, 108, 6045; d) D. L. J. Clive, R. Sunasee, Org. Lett. 2007, 9, 2677. synthesis of heteroatom fluorenes: e) M. Tobisu, Y. Kita, Y. Ano, N. Chatani, J. Am. Chem. Soc. 2008, 130, 15982.
5 a) E. M. Beccalli, G. Broggini, M. Martinelli, S. Sottocornola, Chem. Rev. 2007, 107, 5318; b) D. Alberico, M. E. Scott, M. Lautens, Chem. Rev. 2007, 107, 174.
6 a) G. Dyker, Angew. Chem. Int. Ed. 1992, 21, 1023; b) G. Dyker, Angew. Chem. Int. Ed. 1994, 33, 103.
7 a) M. Chaumontet, R. Piccardi, N. Audic, J. Hitce, J.-L. Peglion, E. Clot, O. Baudoin, J. Am. Chem. Soc. 2008, 130, 15157; b) O. Baudoin, A. Herrbach, F. Guéritte, Angew. Chem. Int. Ed. 2003, 42, 5736.
8 a) V. G. Zaitsev, D. Shabashov, O. Daugulis, J. Am. Chem. Soc. 2005, 127, 13154; b) D. Shabashov, O. Daugulis, Org. Lett. 2005, 7, 3657.
9 a) C.-G. Dong, Q.-S. Hu, Angew. Chem. Int. Ed. 2006, 45, 2289; b) C.-G. Dong, Q.-S. Hu, Tetrahedron. 2008, 64, 2537.
10 T.-P. Liu, C.-H. Xing, Q.-S. Hu, Angew. Chem. Int. Ed. 2010, 49, 2909.
11 a) K. Fuchibe, T. Akiyama, J. Am. Chem. Soc. 2006, 128, 1434; b) T. Y. Gu, W. P. Weber, J. Org. Chem. 1980, 45, 2541.
12 a) T. Hadizad, J. Zhang, D. Yan, Z. Y. Wang, J. P. M. Serbena, M. S. Meruvia, I. A. Huümmelgen, J. mater. sci., Mater. Electron. 2007, 18, 903; b) E. Jeong, S. H. Kim, I. H. Jung, Y. Xia, K. Lee, H. Suh, H.-K. Shim, H. Y. Woo, J. polym. sci., A, Polym. chem. 2009, 47, 3467; c) W.-C. Yen, B. Pal, J.-S. Yang, Y.-C. Hung, S.-T. Lin,C.-Y. Chao, W.-F. Su, J. polym. sci., A, Polym. chem. 2009, 47, 5044; d) S. Merlet, M. Birau, Z. Y. Wang, Org. Lett. 2002, 4, 2157; e) T. Hadizad, J. Zhang, Z. Y. Wang, T. C. Gorjanc, C. Py, Org. Lett. 2005, 7, 795.
13 D. L. J. Clive and R. Sunasee, Org. Lett. 2007, 9, 2677.