meso-Arylporpholactones and their Reduction Products
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- 作者：Christian Br眉ckner ; Junichi Ogikubo ; Jason R. McCarthy ; Joshua Akhigbe ; Michael A. Hyland ; Pedro Daddario ; Jill L. Worlinsky ; Matthias Zeller ; James T. Engle ; Christopher J. Ziegler ; Matthew J. Ranaghan ; Megan N. Sandberg ; Robert R. Birge
- 刊名：The Journal of Organic Chemistry
- 出版年：2012
- 出版时间：August 3, 2012
- 年：2012
- 卷：77
- 期：15
- 页码：6480-6494
- 全文大小：729K
- 年卷期：v.77,no.15(August 3, 2012)
- ISSN：1520-6904
文摘
The rational syntheses of meso-tetraaryl-3-oxo-2-oxaporphyrins 5, known as porpholactones, via MnO4鈥?/sup>-mediated oxidations of the corresponding meso-tetraaryl-2,3-dihydroxychlorins (7) is detailed. Since chlorin 7 is prepared from the parent porphyrin 1, this amounts to a 2-step replacement of a pyrrole moiety in 1 by an oxazolone moiety. The stepwise reduction of the porpholactone 5 results in the formation of chlorin analogues, meso-tetraaryl-3-hydroxy-2-oxachlorin (11) and meso-tetraaryl-2-oxachlorins (12). The reactivity of 11 with respect to nucleophilic substitution by O-, N-, and S-nucleophiles is described. The profound photophysical consequences of the formal replacement of a pyrrole with an oxazolone (porphyrin-like chromophore) or (substituted) oxazole moiety (chlorin-like chromophore with, for the parent oxazolochlorin 12, red-shifted Qx band with enhanced oscillator strengths) are detailed and rationalized on the basis of SAC鈥揅I and MNDO-PSDCI molecular orbital theory calculations. The single crystal X-ray structures of the porpholactones point at a minor steric interaction between the carbonyl oxygen and the flanking phenyl group. The essentially planar structures of all chromophores in all oxidation states prove that the observed optical properties originate from the intrinsic electronic properties of the chromophores and are not subject to conformational modulation.