Electron Transfer Photochemistry of Sabinene: Nucleophilic Capture of a Stereorigid Vinylcyclopropane Radical Cation

Weng, Hengxin; Sethuraman, Venkat; Roth, Heinz D.

doi:10.1021/ja00095a003

Cited by 34 publications

(20 citation statements)

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“…This is shown most clearly by the fact that β-phellandrene (3), the main product formed with DCB as sensitizer, [27] is not observed at all in the TPT-sensitized reaction. This is shown most clearly by the fact that β-phellandrene (3), the main product formed with DCB as sensitizer, [27] is not observed at all in the TPT-sensitized reaction.…”

Section: Discussionmentioning

confidence: 99%

“…[23][24][25][26][27] As a result, appropriate donor molecules may undergo a net conversion amounting to ''substitution'' of an activated H atom by a p-cyanophenyl group. With DCB as sensitizer, the geminate radical anion is a poor base as well as a poor hydrogen-atom acceptor; however, it readily undergoes aromatic substitution with loss of cyanide ion.…”

Section: Discussionmentioning

confidence: 99%

“…vinylcyclopropane systems [sabinene (1), [27] α-(2) and βthujene, [28] 2-carene], [29] and vinylcyclobutane species (αand β-pinene). [25,26,30] In a few cases, the intramolecular capture of terpene radical cations by tethered nucleophiles (OH functions) was probed.…”

Section: Introductionmentioning

confidence: 99%

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Triphenylpyrylium Tetrafluoroborate-Sensitized Photochemistry of the Terpenes Sabinene, α-Phellandrene, and α- and γ-Terpinene

Climent

Miranda²,

Roth³

2000

Eur. J. Org. Chem.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Triphenylpyrylium Tetrafluoroborate-Sensitized Photochemistry of the Terpenes Sabinene, α-Phellandrene, and α- and γ-Terpinene

Climent

Miranda²,

Roth³

2000

Eur. J. Org. Chem.

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“…This reaction typically results in ring-opened products bearing either an alkoxy group (e.g., 6, R ϭ CH 3 ) or an alkoxy and a pcyanophenyl group (e.g., 7); these products are formed by the well-established nucleophilic capture of the corresponding radical cation by the alcohol with ring-opening. [8,9,22,23] In the reaction of trans-1, no isomerization products were observed; apparently nucleophilic capture is faster than isomerization.…”

Section: Solution Photochemistry Of Trans-1mentioning

confidence: 94%

Oxidation of Aryl- and Diarylcyclopropanes in a Pentasil Zeolite: Ring Opening with Deprotonation or Net Hydrogen Migration

Herbertz

Lakkaraju²,

Blume

et al. 2000

Eur. J. Org. Chem.

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“…The attack occurs at a cyclopropane carbon, forms an ally1 free radical, and relieves ring strain (ref. 6,8,9). pThujene, 3, is attacked at the tertiary carbon, whereas 1,2 and 4 are attacked at the quaternary center.…”

Section: Reactions Of Terpenes Containing a Vinylcyclopropane Systemmentioning

confidence: 99%

Electron transfer photochemistry of bifunctional strained-ring and unsaturated systems

Roth¹,

Weng²,

Zhou³

et al. 1997

Pure and Applied Chemistry

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Abstract:Organic radical cations, generated by electron transfer from bi-or trifunctional donor terpenes to photo-excited acceptors, undergo a variety of intra-and intermolecular reactions, including nucleophilic capture and sigmatropic shifts, deprotonation, intramolecular nucleophilic capture, and various cyclizations.The structures and reactions of organic radical cations have been the focus of much interest for the past two decades (ref. 1,2). A rich variety of substrates have been investigated by physical and chemical techniques to delineate changes in geometry upon oxidation, to assess the spin density distribution in the radical cations, and to elucidate parameters affecting their structures (ref. 2,3). Particularly the interactions between adjacent functions, conjugated or nonconjugated, pairs of olefinic a-systems or strained rings, or of strained ring moieties with olefinic fragments has attracted considerable interest (ref. 3).We discuss attempts to utilize light-induced radical cation reactions for synthetidpreparative purposes. We have studied photosensitized reactions of various donors with two or three functional groups, including unsaturated and strained ring moieties as well as an alcohol function as an intramolecular nucleophile. The sensitizers were chosen to give the putative electron transfer reaction either a marginal (-AG -0.1 eV) or a more substantial driving force (-AG > 0.5 eV). The driving force for radical ion formation can be further varied by using a variety of solvents with different polarities; the rates of back electron transfer can be varied by conducting the reactions with or without a co-sensitizer. One significant question in radical cation chemistry concerns the relationship between structure and reactivity. Since, the reactivity depends largely on I the distribution of unpaired spin and positive charge in the intermediate, we will discuss structural features of some radical cations derived from bicyclic vinylcyclopropanes. Structures of Vinylcyclopropane Radical CationsThe structures of vinylcyclopropane radical cations can be assigned by considering the frontier molecular orbital (FMO) of the cyclopropane unit and the interaction between the two moieties. Cyclopropane has a degenerate pair of in-plane e' orbitals (s, a); ionization results in a doubly degenerate 2E' state; first-order Jahn-Teller distortion leads to two non-degenerate electronic states, 2A1 and 2B2 (C2v symmetry) (ref. 4). The 2A1 component (orbital s singly occupied) relaxes to a "one-electron-bonded trimethylene" structure (type A) with one lengthened C-C bond. The alternative 2B2 component has the antisymmetrical molecular orbital a singly occupied; it gives rise to a structure with two lengthened C-C bonds resembling a "acomplex" (type B) (ref. 5).Radical cations of substrates containing strained rings and alkene groups may be stabilized by delocalization of spin and charge. We discuss the structures of four vinylcyclopropane radical cations in which the two functionalities are locked in either the ant...

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Electron Transfer Photochemistry of Sabinene: Nucleophilic Capture of a Stereorigid Vinylcyclopropane Radical Cation

Cited by 34 publications

References 0 publications

Triphenylpyrylium Tetrafluoroborate-Sensitized Photochemistry of the Terpenes Sabinene, α-Phellandrene, and α- and γ-Terpinene

Triphenylpyrylium Tetrafluoroborate-Sensitized Photochemistry of the Terpenes Sabinene, α-Phellandrene, and α- and γ-Terpinene

Oxidation of Aryl- and Diarylcyclopropanes in a Pentasil Zeolite: Ring Opening with Deprotonation or Net Hydrogen Migration

Electron transfer photochemistry of bifunctional strained-ring and unsaturated systems

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