Reaction of singlet oxygen with 4-methyl-2,3-dihydro-.gamma.-pyrans

Frimer, Aryeh A.; Bartlett, Paul D.; Boschung, André F.; Jewett, John G.

doi:10.1021/ja00466a033

Cited by 63 publications

(18 citation statements)

References 6 publications

(10 reference statements)

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“…-The present results resemble those obtained from molecules sharing similar structural features such as 3,4-dihydro-2H-pyrans [3] and enol ethers [9][ lo], in that the product composition is a reflection of solvent polarity. However, there are important differences (vide infra) .…”

supporting

confidence: 82%

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Mechanistic and Synthetic Studies on the Formation of 1,2,4‐Trioxanes Related to Arteannuin. Photooxygenation of a bicyclic dihydropyran

Jefford

Wang

Bérnardinelli

1988

Helvetica Chimica Acta

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supporting

confidence: 82%

“…An apt example is provided by 3,4-dihydro-2H-pyran (1) [3]. Polar solvents favor the formation of the formyl formate 3, arising from the cleavage of the nonisolated intermediate dioxetane 2, whereas in nonpolar solvents, hydroperoxide 4 prevails, ultimately undergoing dehydration to the a$ -unsaturated ketone 5.…”

mentioning

confidence: 99%

Mechanistic and Synthetic Studies on the Formation of 1,2,4‐Trioxanes Related to Arteannuin. Photooxygenation of a bicyclic dihydropyran

Jefford

Wang

Bérnardinelli

1988

Helvetica Chimica Acta

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“…Solvent polarity effects have led some researchers to postulate the intervention either of more or less loosely structured exciplexes, or of peroxiranes, not only for the ene mode, but also for the [π2+π2] and the [π4+π2] reactions 11, 16, 18, 23–25. Evidence for the intervention of a peroxirane species in [π2+π2] cycloadditions is somewhat less persuasive than for the ene reaction,15, 28–31 although the ene pathway seems to be less polar than the pathway for dioxetane formation (this has been inferred from the observation that dioxetane formation can be enhanced by an increase in solvent polarity, and can become the preferential pathway, or even the only one) 15, 18–20. In fact, some indications for the involvement of open‐chain zwitterion intermediates are also given in the literature 26, 27…”

Section: Introductionmentioning

confidence: 99%

The ¹Δ_g Dioxygen Ene Reaction with Propene: A Density Functional and Multireference Perturbation Theory Mechanistic Study

Maranzana¹,

Ghigo²,

Tonachini³

2003

Chemistry A European J

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This study aims to determine whether a balance between concerted and non-concerted pathways exists, and in particular to ascertain the possible role of diradical/zwitterion or peroxirane intermediates. Three non-concerted pathways, via 1) diradical or 2) peroxirane intermediates, and 3) by means of hydrogen-abstraction/radical recoupling, plus one concerted pathway (4), are explored. The intermediates and transition structures (TS) are optimized at the DFT(MPW1K), DFT(B3LYP) and CASSCF levels of theory. The latter optimizations are followed by multireference perturbative CASPT2 energy calculations. (1) The polar diradical forms from the separate reactants by surmounting a barrier (deltaE(++)(MPW1K)=12, deltaE++(B3LYP)=14, and deltaE(++)(CASPT2)=16 kcal mol(-1) and can back-dissociate through the same TS, with barriers of 11 (MPW1K) and 8 kcal mol(-1) (B3LYP and CASPT2). The diradical to hydroperoxide transformation is easy at all levels (deltaE(++)(MPW1K)<4, deltaE(++)(B3LYP)=1 and deltaE(++)(CASPT2)=1 kcal mol(-1)). (2) Peroxirane is attainable only by passing through the diradical intermediate, and not directly, due to the nature of the critical points involved. It is located higher in energy than the diradical by 12 kcal mol(-1), at all theory levels. The energy barrier for the diradical to cis-peroxirane transformation (deltaE(++)=14-16 kcal mol(-1)) is much higher than that for the diradical transformation to the hydroperoxide. In addition, peroxirane can very easily back-transform to the diradical (deltaE(++)<3 kcal mol(-1)). Not only the energetics, but also the qualitative features of the energy hypersurface, prevent a pathway connecting the peroxirane to the hydroperoxide at all levels of theory. (3) The last two-step pathway (hydrogen-abstraction by (1)O(2), followed by HOO-allyl radical coupling) is not competitive with the diradical mechanism. (4) A concerted pathway is carefully investigated, and deemed an artifact of restricted DFT calculations. Finally, the possible ene/[pi2+pi2] competition is discussed.

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“…Notable examples are furnished by 2,5-dimethy1-2,4-hexadiene [ 3 ] , dihydropyran [4], methyl-2,3-dihydro-y-pyran [5], methoxymethylidenecyclohexane [6]. 1 -ethylthio-2-ethyl-l -hexene, and its 1-ethoxy analogue [7].…”

mentioning

confidence: 99%

The Effect of Solvent on Competing Hydroperoxide and Dioxetane Formation on Photo‐Sensitized Oxygenation of Olefins

Jefford¹,

Kohmoto²

1982

Helvetica Chimica Acta

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SummaryThe rates of the competitive photo-sensitized oxygenation of 2-isobutylideneadamantane (1) and 2-propylidene-adamantane (2) with 1, I-di-t-butyl-2-methoxyethane (3) in various solvents were determined. The rates for 1 and 2 were independent of solvent, whereas that for 3 varied markedly with solvent polarity, Compounds 1 and 2 gave only hydroperoxides while 3 gave dioxetane. These results are interpreted in terms of two competing processes involving little and much charge separation leading to hydroperoxide and dioxetane, respectively.Although information is sparse, it appears that the nature of the solvent has a negligible effect on the rates of photo-oxygenation of those olefins which give exclusively either allylic hydroperoxides

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Reaction of singlet oxygen with 4-methyl-2,3-dihydro-.gamma.-pyrans

Cited by 63 publications

References 6 publications

Mechanistic and Synthetic Studies on the Formation of 1,2,4‐Trioxanes Related to Arteannuin. Photooxygenation of a bicyclic dihydropyran

Mechanistic and Synthetic Studies on the Formation of 1,2,4‐Trioxanes Related to Arteannuin. Photooxygenation of a bicyclic dihydropyran

The ¹Δ_g Dioxygen Ene Reaction with Propene: A Density Functional and Multireference Perturbation Theory Mechanistic Study

The Effect of Solvent on Competing Hydroperoxide and Dioxetane Formation on Photo‐Sensitized Oxygenation of Olefins

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Reaction of singlet oxygen with 4-methyl-2,3-dihydro-.gamma.-pyrans

Cited by 63 publications

References 6 publications

Mechanistic and Synthetic Studies on the Formation of 1,2,4‐Trioxanes Related to Arteannuin. Photooxygenation of a bicyclic dihydropyran

Mechanistic and Synthetic Studies on the Formation of 1,2,4‐Trioxanes Related to Arteannuin. Photooxygenation of a bicyclic dihydropyran

The 1Δg Dioxygen Ene Reaction with Propene: A Density Functional and Multireference Perturbation Theory Mechanistic Study

The Effect of Solvent on Competing Hydroperoxide and Dioxetane Formation on Photo‐Sensitized Oxygenation of Olefins

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The ¹Δ_g Dioxygen Ene Reaction with Propene: A Density Functional and Multireference Perturbation Theory Mechanistic Study