Mechanism of 1,2-cycloaddition of singlet oxygen to alkenes.  Trapping a perepoxide intermediate

Schaap, A. Paul; Faler, Gary R.

doi:10.1021/ja00791a051

Cited by 70 publications

(23 citation statements)

References 2 publications

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“…Contrary to the earlier report [3], scarcely any epoxide is formed in pinacolone. Moreover, no trace of t-butyl acetate was detected').…”

contrasting

confidence: 99%

“…8 (1977) Ad singlet oxygen, produced photochemically using tetraphenylporphin as sensitizer in pinacolone, gave the dioxetane 2 and the epoxide 3 (Scheme 2). Particularly intriguing was the conclusion that the epoxide derived from the hypothetical perepoxide 4 through the intervention of pinacolone which was allegedly oxidized to t-butyl acetate (Scheme 3) [3]. It was later discovered that expoxide 3 was formed in substantial amounts even in inert solvents [4].…”

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confidence: 99%

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The Reaction of Biadamantylidene with Singlet Oxygen in the Presence of Dyes [1]

Jefford¹,

Boschung²

1977

Helvetica Chimica Acta

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SummarySinglet oxygen, generated chemically or photogenetically, reacts with biadamantylidene to give the corresponding dioxetane and epoxide only. When methylene blue (MB) or meso-tetraphenylporphin (m-TPP) is used as sensitizer the normal reaction course occurs giving dioxetane as the preponderant product in 2-propanol, ethyl acetate, acetone, pinacolone, methylene chloride, chloroform, carbon tetrachloride and benzene, although in the last two solvents some 10-25% of epoxide is formed. When erythrosin and rose bengal (RB) are used, epoxide becomes the main product (70-95%). Epoxide does not derive from chemical reaction with the solvent. Pinacolone, for example, is not oxidized to t-butyl acetate.The rose bengal reaction involves both singlet oxygen and radicals, since diazabicyclooctane (DABCO) and di-t-butyl-p-cresol interfere with the oxidation. A mechanistic scheme is proposed in which sensitizer and oxygen combine to produce sensitizer radical cation and superoxide radical anion. Subsequently, hydroperoxy radical, deriving from superoxide, reacts with substrate to give epoxide and hydroxy radical. The latter adds to substrate to give a new radical which captures triplet oxygen. Epoxide is formed by loss of hydroperoxy .radical and the chain starts anew. The dioxetane is formed separately either by [2 + 21-cycloaddition or stepwise addition.

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“…Contrary to the earlier report [3], scarcely any epoxide is formed in pinacolone. Moreover, no trace of t-butyl acetate was detected').…”

contrasting

confidence: 99%

mentioning

confidence: 99%

The Reaction of Biadamantylidene with Singlet Oxygen in the Presence of Dyes [1]

Jefford¹,

Boschung²

1977

Helvetica Chimica Acta

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“…Photosensitized oxidation of adamantylideneadamantane in pinacolone produces a mixture of dioxetane and epoxide (6). It was proposed that the epoxide was formed from a perepoxide by transfer of an oxygen atom to pinacolone in a Bayer-Villiger type of reaction and that perepoxide not trapped in this way rearranged to the dioxetane.…”

Section: Discussionmentioning

confidence: 99%

Perepoxide intermediates in the conversion of some β-halohydroperoxides to allylic hydroperoxides by base

Kopecky¹,

Scott²,

Lockwood³

et al. 1978

Can. J. Chem.

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. Migration of the hydroperoxy group occurs during the reaction between base and several 0-halohydroperoxides to give allylic hydroperoxides. An 86: 14 ratio of 3-hydroperoxy-2-(4-methoxypheny1)-3-methyl-I-butene-3-hydroperoxy-3-(4-methoxyphenyl)-2-methyl-I-butene was formed in 90% yield from 2-bromo-3-hydroperoxy-3-(4-methoxyphenyl)-2-methylbutane. From I-chloro-, I-bromo-, and I -iodo-I-(I-hydroperoxy-I-methylethy1)cyclohexane there were obtained I-(I-hydroperoxy-1-methylethyl)cyclohexene and I-hydroperoxy-I-(2-propeny1)-cyclohexane in ratios of 93:7, 94:6, and 94:6, respectively, in 98-100% yield. Isopropylidenecyclohexane was converted with singlet oxygen t o these allylic hydroperoxides in a 10:90 ratio. Only the latter allylic hydroperoxide was formed in the reaction between the alkene and triphenyl phosphite ozonide at -70°C. The p-nitrobenzoate esters of I-hydroperoxy(1-chloro-, I-bromo-, and I-iodo-I-methylethyl)cyclopentane were converted quantitatively to I-(I-hydroperoxy-I-methylethyl)cyclopentene and I-hydroperoxy-I-(2-propeny1)-cyclopentane in 77:23, 73:27, and 70:30 ratios, respectively. Oxidation of isopropylidenecyclopentane with triphenyl phosphite ozonide at -70°C and singlet oxygen produced the allylic hydroperoxides in 62:38 and 58:42 ratios, respectively. The reactions of the p-halohydroperoxides proceed exclusively via perepoxide intermediates. T h e reactions between the alkenes and singlet oxygen or triphenyl phosphite ozonide do not involve perepoxide intermediates.

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“…[82]. A perepoxide intermediate was reported to be trapped in the epoxide form [83] in the reaction of adamantylideneadamantane with singlet oxygen affording dioxetane derivatives [84]. …”

Section: Quasi-intermediate Perepoxidementioning

confidence: 99%

A Mechanistic Spectrum of Chemical Reactions

Inagaki

2009

Orbitals in Chemistry

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The mechanism of chemical reactions between electron donors and acceptors continuously changes with the power of the donors and the acceptors. The interaction between the HOMO (d) of the donors and the LUMO (a*) of the acceptors or delocalization of electrons is important for the reactions. The electron d-to-a* transferred configuration mixes to a significant extent. As the donors and/or the acceptors are strong, their excited configurations appreciably mixes together with the transferred configuration. The d-a and d*-a* orbital interactions are important in addition to the d-a* interaction. Reactions have features characteristic of the excited-state reactions although the donor-acceptor system is not really excited, but in the ground state. This process is termed pseudoexcitation. The a-d-a*-d* interaction is important. For much stronger donors and acceptors, the electron transferred configuration is stable and predominant. Covalent bonds do not form but instead ionic pairs, and electron transfer results. A mechanistic spectrum of chemical reactions is composed of the delocalization, pseudoexcitation, and electron transfer bands.

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Mechanism of 1,2-cycloaddition of singlet oxygen to alkenes. Trapping a perepoxide intermediate

Abstract: 6 6 5 J = J = 9H,, 1 H }H .55, d of s e p t , ]H 9 H,, 1.2, 1 H 6 1.48, s, 6 H 6 1.83 a n d 1.72, e a c h a 3 H, d, J = 1.2 Hz 9 sion to aldehyde 3 and acetone on warming in CCI, solution (37 min half-life at 44"), and by the chemi-

Cited by 70 publications

References 2 publications

The Reaction of Biadamantylidene with Singlet Oxygen in the Presence of Dyes [1]

The Reaction of Biadamantylidene with Singlet Oxygen in the Presence of Dyes [1]

Perepoxide intermediates in the conversion of some β-halohydroperoxides to allylic hydroperoxides by base

A Mechanistic Spectrum of Chemical Reactions

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