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Abstract A density functional theoretical (DFT) study is presented, implicating a1O2oxidation process to reach a dihydrobenzofuran from the reaction of the natural homoallylic alcohol, glycocitrine. Our results predict an interconversion between glycocitrine and aniso‐hydroperoxide intermediate [R(H)O+–O−] that provides a key path in the chemistry which then follows. Formations of allylic hydroperoxides are unlikely from a1O2‘ene’ reaction. Instead, the dihydrobenzofuran arises by1O2oxidation facilitated by a 16° curvature of the glycocitrine ring imposed by a pyramidalN‐methyl group. This curvature facilitates the formation of theiso‐hydroperoxide, which is analogous to theisospecies CH2I+–I−and CHI2+–I−formed by UV photolysis of CH2I2and CHI3. Theiso‐hydroperoxide is also structurally reminiscent of carbonyl oxides (R2C=O+–O−) formed in the reaction of carbenes and oxygen. Our DFT results point to intermolecular process, in which theiso‐hydroperoxide's fate relates to O‐transfer and H2O dehydration reactions for new insight into the biosynthesis of dihydrobenzofuran natural products.
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Estimation of Singlet Oxygen Quantum Yield Using Novel Green‐Absorbing Baird‐type Aromatic Photosensitizers †
Abstract We report two new organic green‐absorbing singlet oxygen (1O2) photosensitizers: Quinoidal naphthyl thioamide (QDM) andbis‐iodol‐dipyrrolonaphthyridine‐dione (I2–DPND), with triplet energies of 40.8 and 47.5 kcal mol−1(at 77 K in a glassy matrix) , respectively. The UV–vis absorption and emission characteristics ofQDMandI2–DPNDare similar to other commercially available organic1O2photosensitizers such as Rose Bengal, which was used as standard/reference to estimate the1O2quantum yield (Φ∆) of the chromophores under study. Using 9,10‐diphenylanthracene (DPA) as an1O2quencher, we estimated the Φ∆≈ 67–85% forQDMand Φ∆≈ 25–32% forI2–DPND. The discrepancy in the Φ∆values could be explained by the apparent photo‐decomposition of the later dye. Nevertheless, the high Φ∆value forQDMis unprecedented, as this chromophore exhibits relatively low structural complexity and could further be derivatized to create novel photodynamic agents.
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- Award ID(s):
- 2211296
- PAR ID:
- 10448140
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Photochemistry and Photobiology
- Volume:
- 98
- Issue:
- 1
- ISSN:
- 0031-8655
- Page Range / eLocation ID:
- p. 57-61
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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