ORGANIC
LETTERS
2011
Vol. 13, No. 9
2498–2501
meso-Aryl Triphyrin(2.1.1)
K. S. Anju,† S. Ramakrishnan,† and A. Srinivasan*,‡
Photosciences and Photonics Section, Chemical Sciences and Technology Division,
National Institute for Interdisciplinary Science and Technology (NIIST-CSIR),
Thiruvananthapuram-695 019, Kerala, India, and School of Chemical Sciences,
National Institute of Science Education and Research (NISER), Bhubaneswar-751005,
Orissa, India
Received March 21, 2011
ABSTRACT
Synthesis, spectral, and single-crystal X-ray structural analysis of meso-aryl triphyrin(2.1.1) featuring three pyrrole rings and four meso-aryl rings
are described. The title compound represents the first example of a ring-contracted meso-aryl β-unsubstituted free-base triphyrin containing only
pyrrole rings reported to date and generates 2-D supramolecular assembly in the solid state.
Porphyrins, the most widely explored macrocyclic sys-
tems, reveal their structural versatility by forming large
families of expanded, contracted, and isomeric analogues.
Among contracted porphyrinoids, subporphyrins are the
real ring-contracted congener and are relatively new en-
tries. The first subporphyrin, tribenzosubporphine (3)
with similar electronic structure to subphthalocyanines
(1),1 was prepared by the group of Osuka in 2006 as
B(III) complex under harsh reaction conditions.2 Shortly
thereafter, the groups of Kobayashi3a,c and Osuka3b in-
dependently reported more facile methods for the synth-
eses of meso-aryl subporphyrins (4) (Figure 1). Since then,
a variety of substituents have been introduced in the meso,4 β,5
and axial positions.2,6 Subporphyrins feature an intense
(4) (a) Inokuma, Y.; Osuka, A. Chem. Commun. 2007, 2938–2940. (b)
Xu, T.; Lu, R.; Liu, X.; Chen, P.; Qiu, X.; Zhao, Y. Eur. J. Org. Chem.
2008, 1065–1071. (c) Inokuma, Y.; Easwaramoorthi, S.; Jang, S. Y.;
Kim, K. S.; Kim, D.; Osuka, A. Angew. Chem., Int. Ed. 2008, 47, 4840–
4843. (d) Inokuma, Y.; Easwaramoorthi, S.; Yoon, Z. S.; Kim, D.;
Osuka, A. J. Am. Chem. Soc. 2008, 130, 12234–12235. (e) Liu, X.; Lu, R.;
Xu, T.; Xu, D.; Zhan, Y.; Chen, P.; Qiu, X.; Zhao, Y. Eur. J. Org. Chem.
2009, 53–60. (f) Hayashi, S.; Inokuma, Y.; Easwaramoorthi, S.; Kim,
K. S.; Kim, D.; Osuka, A. Angew. Chem., Int. Ed. 2010, 49, 321–324.
(5) Tsurumaki, E.; Inokuma, Y.; Easwaramoorthi, S.; Lim, J. M.;
Kim, D.; Osuka, A. Chem.;Eur. J. 2009, 15, 237–247.
† National Institute for Interdisciplinary Science and Technology.
‡ National Institute of Science Education and Research.
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Kietaibl, H. Monatsh. Chem. 1974, 105, 405–418. (c) Kobayashi, N. J.
Chem. Soc., Chem. Commun. 1991, 1203–1205. (d) Kobayashi, N.;
Ishizaki, T.; Ishii, K.; Konami, H. J. Am. Chem. Soc. 1999, 121, 9096–
9110. (e) Fukuda, T.; Stork, J. R.; Potucek, R. J.; Olmstead, M. M.; Noll,
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´
ꢀ
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r
10.1021/ol200668a
Published on Web 04/12/2011
2011 American Chemical Society