Novel Route to Functionalized Tetraaryltetra[2,3]naphthaloporphyrins via Oxidative Aromatization Olga S. Finikova, † Andrei V. Cheprakov, ‡ Patrick J. Carroll, § and Sergei A. Vinogradov* ,† Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, Department of Chemistry, Moscow State University, Moscow 119899, Russia, and Department of Chemistry, Crystallographic Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania 19104 vinograd@mail.med.upenn.edu Received June 6, 2003 Abstract: A novel general route to substituted meso- tetraaryltetra[2,3]naphthaloporphyrins (Ar 4 TNP) and meso- tetraaryloctamethoxytetra[2,3]naphthaloporphyrins (Ar 4 - (MeO) 8 TNP) via oxidative aromatization of nonaromatically fused porphyrin precursors is described. Ar 4 (MeO) 8 TNPs exhibit more red-shifted absorption bands than Ar 4 TNPs and differ dramatically in solubility. The first X-ray crystal- lographic structure of tetranaphthaloporphyrin, i.e., PdAr 4 - TNP (Ar ) 4-MeO 2 CC 6 H 4 ), revealed that the degree of nonplanar distortion of this macrocycle is only slightly higher than that of the homologous tetrabenzoporphyrins (Ar 4 TBP). Porphyrins extended via fusion with external aromatic rings 1 exhibit remarkably red-shifted absorption bands and strong room temperature luminescence. The simplest representatives of laterally extended porphyrins, meso- tetraaryltetrabenzoporphyrins (Ar 4 TBP), have already been shown to be of interest for biomedical 2 and nonlinear optical applications. 3 At the same time, the next group in the extended porphyrin family, i.e., tetranaphthalopor- phyrins, have been explored only minimally, 4 despite their great potential for PDT, 4d medical oxygen imaging, 4e and electrooptical 4c applications. Naphthalo extension of the core pyrrole moiety leads to an array of isomeric tetranaphthaloporphyrins. 1b Among them, tetra[2,3]naphthaloporphyrins (TNP) and their more soluble analogues meso-tetraaryltetra[2,3]- naphthaloporphyrins (Ar 4 TNP) 5 are of particular interest due to their higher molecular symmetry and, conse- quently, much narrower and stronger spectral transi- tions. 1 Unfortunately, extremely poor synthetic avail- ability of TNPs and Ar 4 TNPs was a serious obstacle on the way to discovery of their practical potential. The original approach to Ar 4 TNPs, 6 based on a high- temperature template condensation of [2,3]naphthalene- dicarboximide with arylacetic acids, was of low practi- cality due to the required severe reaction conditions, extremely low yields (<1%), 4f and laborious purifications. Recently, a new approach to TNPs has been developed that makes use of the retro-Diels-Alder reaction. 7 This method affords Ar 4 TNPs in excellent yields (at the last step of the reaction sequence) but does not permit the introduction of substituents into the fused aromatic rings. In our own effort to develop approaches to aromatically annulated porphyrins, we recently came across a useful strategy based on oxidative aromatization of porphyrins fused with nonaromatic cyclohexene rings. 8 Using this method, a large variety of polyfunctionalized Ar 4 TBPs could be obtained in very good yields. Naturally, the question of whether this methodology can be extended to the synthesis of Ar 4 TNPs was raised. Oxidative aro- matization of nonaromatic precursor porphyrins has been in fact employed in the syntheses of tetra[1,2]naph- thaloporphyrins, 9 mono[1,2]- 10,11 and di[1,2]naphthalo- porphyrins, 10,12 and a mono[2,3]naphthaloporphyrin. 13 * To whom correspondence should be addressed. Phone: (215) 898- 6382. Fax: (215) 573-3787. † Department of Biochemistry and Biophysics, University of Penn- sylvania. ‡ Department of Chemistry, Moscow State University. § Crystallographic Laboratory, University of Pennsylvania. (1) For a review, see: (a) Lash, T. D. Synthesis of novel porphyrinoid chromophores. In The Porphyrin Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.; Academic Press: New York, 2000 Chapter 10. (b) Lash, T. D. J. Porph. Phthal. 2001, 5, 267-288. (2) (a) Yasuike, M.; Yamaoka, T.; Ohno, O.; Sakuragi, M.; Ichimura, K. Inorg. Chim. Acta 1991, 184, 191-195. (b) Lavi, A.; Johnson, F. M.; Ehrenberg, B. Chem. Phys. Lett. 1994, 231, 144-150. (c) Vinogra- dov, S. A.; Lo, L.-W.; Jenkins, W. T.; Evans, S. M.; Koch, C.; Wilson, D. F. Biophys. J. 1996, 70, 1609-1617. (d) Finikova, O.; Galkin, A.; Rozhkov, V.; Cordero, M.; Ha ¨ gerha ¨ ll, C.; Vinogradov, S. J. Am. Chem. Soc. 2003, 125, 4882-4893. (e) Rietveld, I. B.; Kim, E.; Vinogradov, S. A. 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