963
T. Iwai et al.
Letter
Synlett
Ph
COOMe
Ph
7, 20%
C70 (7)
(1.0 equiv)
n-Bu4NOH
(1.0 equiv)
bisadducts 9, 17%
Ph
+
COOMe
hν,
110 °C, 2 h
ODCB–H2O
r.t., 0.5 h
NNHTs
COOMe
3a
α-isomer
β-isomers
monoadducts 8, 49% (α/β = 85:15)
Scheme 3 Direct synthesis of [6,6]PC71BM (8) under photoirradiation conditions
thesized from the corresponding tosylhydrazones 3b–d.
Without photoirradiation, the benzothiophene derivative
was obtained as the [5,6]fulleroid 2b (Table 2, entry 1), sim-
ilar to the synthesis of PC61BM. However, under photoirra-
diation conditions, [6,6]methanofullerene 1b was directly
synthesized (Table 2, entry 2). On the other hand, thieno-
thiophene derivatives 1c and 1d were directly converted
into the [6,6]methanofullerene without photoirradiation,
as reported by Matsumoto et al. (Table 2, entries 3 and 4).8d
Hummelen et al. also synthesized PC71BM (8),7h the
higher fullerene analogue of PC61BM. C70 (7) has a higher
absorption coefficient in the visible region of the spectrum;
therefore, C70 derivatives are regarded as some of the most
promising acceptor molecules for organic photovoltaics.
PC71BM (8) was synthesized using the optimized reaction
conditions and irradiation with a 375 W incandescent lamp
for two hours and was obtained in 49% isolated yield with
17% of bisadducts 9 and 20% of unreacted C70 (7) (Scheme
3). The obtained monoadducts 8 consisted of the three in-
separable isomers (α-type and two kinds of β-type) in a ra-
tio similar to that previously reported.7h
In conclusion, we have developed a facile synthetic
method to obtain methanofullerenes, such as PC61BM. This
aqueous two-phase system with quaternary ammonium
hydroxide under photoirradiation conditions gave repro-
ducible results and avoids the need for laborious anhydrous
conditions and excess amount of reagents. PC61BM, PC71BM,
and some thienyl analogues could be obtained in good
yields. Further exploration to improve the yield and selec-
tivity for the monoadducts are now in progress, including
the utilization of flow synthesis.18
References and Notes
(1) (a) Matsuo, Y. Chem. Lett. 2012, 41, 754. (b) Brabec, C. J.;
Gowrisanker, S.; Halls, J. J. M.; Laird, D.; Jia, S.; Williams, S. P.
Adv. Mater. 2010, 22, 3839. (c) Dennler, G.; Schaber, M. C.;
Brabec, C. J. Adv. Mater. 2009, 21, 1323. (d) Brabec, C. J.;
Sariciftci, N. S.; Hummelen, J. C. Adv. Funct. Mater. 2001, 11, 15.
(2) Hummelen, J. C.; Knight, B. W.; LePeq, F.; Wudl, F.; Yao, J.;
Wilkins, C. L. J. Org. Chem. 1995, 60, 532.
(3) Shaheen, S. E.; Brabec, C. J.; Sariciftci, N. S.; Padinger, F.;
Fromherz, T.; Hummelen, J. C. Appl. Phys. Lett. 2001, 78, 841.
(4) Service, R. F. Science 2011, 332, 293.
(5) (a) Dang, M. T.; Hirsch, L.; Wantz, G.; Wuest, J. D. Chem. Rev.
2013, 113, 3734. (b) Dang, M. T.; Hirsch, L.; Wantz, G. Adv. Mater.
2011, 23, 3597. (c) Troshin, P. A.; Hoppe, H.; Renz, J.; Egginger,
M.; Mayorova, J. Y.; Goryachev, A. E.; Peregudov, A. S.;
Lyubovskaya, R. N.; Gobsch, G.; Sariciftci, N. S.; Razumov, V. F.
Adv. Funct. Mater. 2009, 19, 779. (d) Li, G.; Shrotriya, V.; Yao, Y.;
Yang, Y. J. Appl. Phys. 2005, 98, 043704.
(6) (a) Gendron, D.; Morin, P.-O.; Berrouard, P.; Allard, N.; Aïch, B.
R.; Garon, C. N.; Tao, Y.; Leclerc, M. Macromolecules 2011, 44,
7188. (b) Su, M.-S.; Kuo, C.-Y.; Yuan, M.-C.; Jeng, U. S.; Su, C.-J.;
Wei, K.-H. Adv. Mater. 2011, 23, 3315. (c) Price, S. C.; Stuart, A.
C.; Yang, L.; Zhou, H.; You, W. J. Am. Chem. Soc. 2011, 133, 4625.
(d) Piliego, C.; Holcombe, T. W.; Douglas, J. D.; Woo, C. H.;
Beaujuge, P. M.; Fréchet, J. M. J. J. Am. Chem. Soc. 2010, 132,
7595.
(7) (a) Morinaka, Y.; Nobori, M.; Murata, M.; Wakamiya, A.;
Sagawa, T.; Yoshikawa, S.; Murata, Y. Chem. Commun. 2013, 49,
3670. (b) Bouwer, R. K. M.; Hummelen, J. C. Chem. Eur. J. 2010,
16, 11250. (c) Zhao, H.; Guo, X.; Tian, H.; Li, C.; Xie, Z.; Geng, Y.;
Wang, F. J. Mater. Chem. 2010, 20, 3092. (d) Lenes, M.; Shelton, S.
W.; Sieval, A. B.; Kronholm, D. F.; Hummelen, J. C.; Blom, P. W.
M. Adv. Funct. Mater. 2009, 19, 3002. (e) Shu, C.; Xu, W.;
Slebodnick, C.; Champion, H.; Fu, W.; Reid, J. E.; Azurmendi, H.;
Wang, C.; Harich, K.; Dorn, H. C.; Gibson, H. W. Org. Lett. 2009,
11, 1753. (f) Lens, M.; Wetzelaer, G.-J. A. H.; Kooistra, F. B.;
Veenstra, S. C.; Hummelen, J. C.; Blom, P. W. M. Adv. Mater. 2008,
20, 2116. (g) Kooistra, F. B.; Knol, J.; Kastenberg, F.; Popescu, L.
M.; Verhees, W. J. H.; Kroon, J. M.; Hummelen, J. C. Org. Lett.
2007, 9, 551. (h) Wienk, M. M.; Kroon, J. M.; Verhees, W. J. H.;
Knol, J.; Hummelen, J. C.; van Hal, P. A.; Janssen, R. A. J. Angew.
Chem. Int. Ed. 2003, 42, 3371.
Acknowledgment
This research was supported in part by Core Research for Evolutional
Science and Technology (CREST) of the Japan Science and Technology
Agency (JST) and JSPS KAKENHI Grant Number 23750232 and
22550176.
© Georg Thieme Verlag Stuttgart · New York — Synlett 2015, 26, 960–964