Mercury photosensitized extrusion reactions for the preparation of heterocycles

Arnold, Donald R.; Abraitys, V. Y.

doi:10.1016/s0040-4039(01)98395-9

Cited by 4 publications

(2 citation statements)

References 19 publications

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“…Irradiation of 2,3,5,5-Tetratner/lyI-5,6-dihj~dropyrazi?1e (16) at Low Tetnperatrrres A 1.0 g sample of the dlhydropyrazine dissolved in 10 ml of methylcyclohexane:isopentane,4:l,in a Pyrex tube, was purged with nitrogen, sealed, and cooled in liquid nitrogen in a Pyrex dewar to form a glass. This sample was irradiated at liquid nitrogen temperatures with a I kW high-pressure, mercury vapor lamp (General Electric AH6).…”

Section: 2-dimethyl-45-diphenylisoitnin'arole (Ioa)mentioning

confidence: 99%

Electronic Excited States of the Cyclic 1,4-Diaza-1,3-diene (Cyclic α-Diimine) System. Photochemical Reactions of 2H-Isoimidazole, 5,6-Dihydropyrazine, and 1,4-Diazepine Derivatives

Arnold¹,

Abraitys²,

McLeod³

1971

Can. J. Chem.

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The five-, six-, and seven-membered cyclic 1,4-diaza-l,3-dienes have been irradiated under a variety of conditions. The six-membered ring (dihydropyrazine) opens in a 6ne valence isomerization reaction. The resulting enediimine is stable at low temperatures and has been characterized (i.r.). Irradiation of 2,3,5,5-tetramethyl-5,6-dihydropyrazine (lb) results in formation of the enediimine 26 which reacts further to give the rearranged monomer 12 and/or dimers 13 depending upon the temperature. The fiveand seven-membered systems are stable to irradiation in inert solvents. However, irradiation of 2,2-dimethyl-4,5-diphenylisoimidazole (10h) in isopropyl alcohol gives the dihydroderivative 19 and in tetramethylethylene the one-to-one adduct 25.The U.V. spectrum of the six-membered ring (5,6-dihydropyrazine) is very different from that of the five-and seven-membered rings. The long wavelength maximum (ca. 350 nm) of the six-membered ring is attributed to a transition directly into an excited state common to the enediimine 2 (i.e., the excited state has a node between C-5 and -6 of the dihydropyrazine).

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Section: 2-dimethyl-45-diphenylisoitnin'arole (Ioa)mentioning

confidence: 99%

Electronic Excited States of the Cyclic 1,4-Diaza-1,3-diene (Cyclic α-Diimine) System. Photochemical Reactions of 2H-Isoimidazole, 5,6-Dihydropyrazine, and 1,4-Diazepine Derivatives

Arnold¹,

Abraitys²,

McLeod³

1971

Can. J. Chem.

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“…Breaking of CC single bonds in the rings, yielding biradicals, can be excluded for the compounds considered here because of the low T 1 energies (between 50 and 60 kcal/mol for styrene derivatives compared to >80 kcal/mol dissociation energy for CC single bonds , ). Because of the central role of the double bond in the process, several reaction pathways which concentrate on this basic chromophore have been proposed: (i) the double bond twist coordinate, ,,, (ii) syn pyramidalization at the double bond, ,, (iii) anti pyramidalization at the double bond, (iv) the CC bond stretching coordinate 4 and (v) a benzene-like 1,6-biradicaloid intermediate structure . Our previous investigation of the potential energy surface for the double bond twist path (i) in the bicyclic alkene norbornene 19 has shown that the surface of the T 1 state is very flat and that the molecule in this state is more flexible than previously thought.…”

Section: Introductionmentioning

confidence: 99%

A Theoretical Study of the Radiationless Decay Mechanism of Cyclic Alkenes in the Lowest Triplet State

Woeller¹,

Peyerimhoff²,

Danovich³

et al. 2000

J. Phys. Chem. A

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The radiationless decay mechanisms of cyclic alkenes C n H 2n-2 (n ) 4, 5, 6), norbornene, their phenyl derivatives, and styrene in their lowest triplet state have been investigated by unrestricted density functional, ab initio CASSCF, and MRD-CI calculations. The potential energy surfaces of the ground (S 0 ) and lowest triplet state (T 1 ) have been explored along double bond twisting and anti pyramidalization reaction pathways to explain the experimentally observed inverse proportionality between ring size and triplet-state lifetime. The calculations for the transition probabilities between T 1 and S 0 states are based on Fermi's golden rule including spin-orbit coupling (SOC) constants. According to the older "free-rotor model", the hindered twist around the double bond in small ring alkenes has been assumed so far to be the main factor determining the T 1 -state lifetimes. All computational results show, however, that only a combined reaction coordinate of anti pyramidalization and twisting at the double bond provides a low-energy pathway which reproduces the experimentally observed transition probabilities. For the relative transition rates, the different Franck-Condon (FC) factors in the series of compounds are found to be much more important than the SOC constants (FCcontrolled mechanism). On the basis of the theoretical model, the effect of substitution of vinylic hydrogen atoms by phenyl groups is discussed.

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ChemInform Abstract: PHOTOSENSIBILISIERTE SPALTUNGSRK. ZUR HERST. VON HETEROCYCLEN

Arnold¹,

Abraitys²

1970

Chemischer Informationsdienst. Organische Chemie

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Mercury photosensitized extrusion reactions for the preparation of heterocycles

Cited by 4 publications

References 19 publications

Electronic Excited States of the Cyclic 1,4-Diaza-1,3-diene (Cyclic α-Diimine) System. Photochemical Reactions of 2H-Isoimidazole, 5,6-Dihydropyrazine, and 1,4-Diazepine Derivatives

Electronic Excited States of the Cyclic 1,4-Diaza-1,3-diene (Cyclic α-Diimine) System. Photochemical Reactions of 2H-Isoimidazole, 5,6-Dihydropyrazine, and 1,4-Diazepine Derivatives

A Theoretical Study of the Radiationless Decay Mechanism of Cyclic Alkenes in the Lowest Triplet State

ChemInform Abstract: PHOTOSENSIBILISIERTE SPALTUNGSRK. ZUR HERST. VON HETEROCYCLEN

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