Photochemical Ring-Opening Reactions of Substituted Chromenes and Isochromenes

Padwa, Albert; Au, Andrew; Lee, George A.; Owens, William

doi:10.1021/jo964025l

Cited by 5 publications

(11 citation statements)

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“…Its short lifetime and the overlapping part of the 1 H spectrum between 7.2 and 7.9 ppm (which hides its resonances) did not allow 2D experiments to characterize it. Padwa et al observed previously an unstable photoproduct resulting from the 1,4 addition of methanol on an o-quinoneallide intermediate (29). This structure is not consistent with the X form because no aliphatic signals were detected in the 1 H NMR spectra.…”

Section: Resultsmentioning

confidence: 95%

NMR Structural and Kinetic Assignment of Fluoro-3H-naphthopyran Photomerocyanines¶

Delbaere

Micheau

Teral³

et al. 2001

Photochem Photobiol

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The kinetic and structural behavior of a photochromic compound, 3-(2-fluorophenyl)-3-phenyl-3H-naphtho[2,1-b]pyran (F-Py), was investigated using 1H and 19F nuclear magnetic resonance (NMR) spectroscopy. Upon irradiation, the four theoretically predicted photomerocyanines appear along with a fifth form X, whose final structure has not been elucidated. This last form and two of the photomerocyanines are thermally labile, whereas the other two do not show any signs of decay. The system has been analyzed by NMR spectroscopy. This led to the structural assignment of each photomerocyanine. The kinetics of the thermal bleaching were monitored by directly and separately measuring the concentrations of each species at regular time intervals using 19F NMR spectroscopy. We therefore propose a plausible reaction mechanism. On the basis of this mechanism, the mathematical treatment and the study of the effects of temperature led to the determination of the kinetic and thermodynamic parameters (rate coefficients, enthalpy and entropy of activation) of this photochromic system. The leading role of the labile intermediate X on the formation of trans-transoid-cis (TTC) and cis-transoid-cis (CTC) photomerocyanines is pointed out.

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Section: Resultsmentioning

confidence: 95%

NMR Structural and Kinetic Assignment of Fluoro-3H-naphthopyran Photomerocyanines¶

Delbaere

Micheau

Teral³

et al. 2001

Photochem Photobiol

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“…In the case of P. kelleyi, the increase in defensive compounds at greater elevation could be attributable to the relationship between increased UVB radiation at higher elevations and the photoactive properties of the prenylated benzoic acid, chromene, and dimeric chromane (Figs S4, S5; Table S1, S2; Krause et al, 1999;Ruhland et al, 2013;Virjamo et al, 2014). UV light is known to affect concentrations of phytochemicals through a variety of mechanisms (Becker & Michl, 1966;Zangerl & Berenbaum, 1987;Downum et al, 1991;Padwa et al, 1996), and plants at higher elevations are exposed to a greater intensity of UV light compared with plants at lower elevations. The association between elevation and P. kelleyi phytochemistry was mostly attributable to changes in the relative concentration of prenylated benzoic acid in the leaves.…”

Section: Discussionmentioning

confidence: 99%

Intraspecific phytochemical variation shapes community and population structure for specialist caterpillars

et al. 2016

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Summary Chemically mediated plant–herbivore interactions contribute to the diversity of terrestrial communities and the diversification of plants and insects. While our understanding of the processes affecting community structure and evolutionary diversification has grown, few studies have investigated how trait variation shapes genetic and species diversity simultaneously in a tropical ecosystem.We investigated secondary metabolite variation among subpopulations of a single plant species, Piper kelleyi (Piperaceae), using high‐performance liquid chromatography (HPLC), to understand associations between plant phytochemistry and host‐specialized caterpillars in the genus Eois (Geometridae: Larentiinae) and associated parasitoid wasps and flies. In addition, we used a genotyping‐by‐sequencing approach to examine the genetic structure of one abundant caterpillar species, Eois encina, in relation to host phytochemical variation.We found substantive concentration differences among three major secondary metabolites, and these differences in chemistry predicted caterpillar and parasitoid community structure among host plant populations. Furthermore, E. encina populations located at high elevations were genetically different from other populations. They fed on plants containing high concentrations of prenylated benzoic acid.Thus, phytochemistry potentially shapes caterpillar and wasp community composition and geographic variation in species interactions, both of which can contribute to diversification of plants and insects.

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“…The generated colored species are thermally unstable; the stability is increased by benzo-annelation in the 5,6-or 7,8-position and conjugative substituents in the 2-position and it is decreased by benzo-annelation in the 6,7-position and bulky substituents in the 4-position 18 . Kolc and Becker then reacted the colored photoproducts obtained from 2H-benzopyrans with lithium aluminum hydride at low temperatures and found the generation of phenol derivatives from infrared, NMR, and absorption spectro- 23 . They also showed that the adducts thermally revert back to the closed form.…”

Section: Photochromic Behavior Of 2h-benzopyransmentioning

confidence: 99%

“…Since both the constituent -electron systems do not interact significantly in the spiro form, the absorption spectrum of the spiropyran molecule is approximately reproduced by the superposition of the spectra of the two individual moieties 16,17 . It has been known that only 2H-benzopyrans (chromenes) and their analogues, which constitute the spiropyran molecules as the pyran moiety, also show photochromic behavior on UV irradiation ( Figure 2) 13,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] . Extensive conjugation of the -electron system in the open form leads to the appearance of the strong absorption in the visible region where the closed form does not absorb.…”

Section: Introductionmentioning

confidence: 99%

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Photochemistry of Photochromic Benzopyrans Studied by Time-Resolved Absorption Spectroscopy

Nakabayashi

Nishi

Sakuragi³

2001

Science Progress

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Photochemical Ring-Opening Reactions of Substituted Chromenes and Isochromenes

Cited by 5 publications

References 1 publication

NMR Structural and Kinetic Assignment of Fluoro-3H-naphthopyran Photomerocyanines¶

NMR Structural and Kinetic Assignment of Fluoro-3H-naphthopyran Photomerocyanines¶

Intraspecific phytochemical variation shapes community and population structure for specialist caterpillars

Photochemistry of Photochromic Benzopyrans Studied by Time-Resolved Absorption Spectroscopy

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