5‐Acetyl‐1,2,3,4,5‐pentamethyl‐bicyclo‐[2.1.0]penten

Of two very proximate syn‐periplanar bisdiazenes (1,2) mono‐, di‐, tri‐ and tetra‐N‐oxides were prepared, representing six combinations of the individual NN/NNO/ONNO chromophores. According to DFT calculations (B3LYP/6‐31G*), [2+2]photocycloaddition to the respective oxidized tetrazetidines is significantly to moderately endothermic. The metathesis isomerization of the oxidized tetrazetidines is generally highly exothermic and kinetically increasingly favorable with increasing oxidation state. In practice, four out of the six bichromophoric combinations undergo selectively, in competition with N2 elimination from a DBH unit (13) still partially, metathesis isomerization upon π → π* excitation (monochromatic 254 nm light). In the case of the syn‐NNO/NNO combinations (5/6, 14), the photoaddition is thermally reversed. For a ONNO/NN combination (30), internal electron transfer is responsible for a complex reaction pattern. The preparative value of the metathesis reactions, though, is limited: The metathesis‐derived bis[diazene mono(di)oxides] undergo relatively fast secondary photoreactions, while the tri(tetra)oxides undergo rapid thermal transformations. For the NN/NNO systems (12), of three potential pathways for its metathesis isomerization, the one that takes place via σ‐symmetric intermediates (63, 64) is excluded by virtue of the retention of optical purity in the photometathesis of a highly enriched enantiomer [(−)‐12]. Matrix irradiation experiments (12 K, IR control) with 12 result in the appearance of a kinetically highly labile transient. Supported by DFT calculations it is concluded that in the metathesis reactions, the respective tetrazetidine oxides (increasingly destabilized by interactions between oxygen lone pairs and NNσ* orbitals) function as vibrationally excited transients. That thermal reversion of these transients might be a general, nonproductive competition, is suggested by the experimental verification of a “reversed photometathesis” (51 → 15) and by the generally low rates in product formation upon irradiation. The question remains to be answered why in structurally analogous molecular skeletons, [2+2]photocycloaddition occurs in the CC/NN and variously oxidized NN/NN, and not, however, in the parent NN/NN combinations.

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Proximate,syn-Periplanar Diazene/Diazene(di)oxy, Diazeneoxy/Diazene(di)oxy, and Diazenedioxy/Diazenedioxy Skeletons: Syntheses, [2+2]Photocycloadditions, Metathesis

Exner

Fischer

Lugan

et al. 2000

Eur. J. Org. Chem.

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Zur Photochemie von 9‐Oxa‐tricyclo[4.2.1.0 ^2.5 ]nonadienen; Synthese von Derivaten des 9‐Oxa‐homokubans

Eberbach

Perroud‐Argüelles

1972

Chem. Ber.

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Oxepine, III. Ein neuer Syntheseweg ausgehend von 2,5‐Cyclohexadien‐1,4‐diolen

1975

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Die Dehydratisierung von 1-R-4-R-2,6-di-tert-butyl-2,5-cyclohexadien-l,4-diolen 9 fuhrt bei konsequenter Ausnutzung der Substituenteneffekte von R und R erstmals zu 2-R-5-R-3,7-di-tertbutyloxepinen 1. Einige chemische Reaktionen sowie die Umlagerung der Oxepine 1 iiber 2.4-Cyclohexadienone 7 in Phenole 15 und die damit verbundenen mechanistischen Konsequenzen (NlH-Shift) werden untersucht. Oxepins, III1.*)A New Synthesis from 2,5-Cyclohexadiene-l,4diolsThe dehydration of 1-R-4-R-2,6-di-tert-butyl-2,5-cyclohexadiene-1,4-diols 9 for the first time yields 2-R-5-R-3,7-di-tert-butyloxepins 1 if the substituents R and R' are properly chosen. Some chemical reactions including the rearrangements of the oxepins 1 via 2,4-cyclohexadienones 7 to the phenols 15 and their mechanistic consequences (NIH shift) are investigated. A. Bisherige Synthesen

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5‐Acetyl‐1,2,3,4,5‐pentamethyl‐bicyclo‐[2.1.0]penten

Cited by 6 publications

References 14 publications

Proximate,syn-Periplanar Diazene/Diazene(di)oxy, Diazeneoxy/Diazene(di)oxy, and Diazenedioxy/Diazenedioxy Skeletons: Syntheses, [2+2]Photocycloadditions, Metathesis

Proximate,syn-Periplanar Diazene/Diazene(di)oxy, Diazeneoxy/Diazene(di)oxy, and Diazenedioxy/Diazenedioxy Skeletons: Syntheses, [2+2]Photocycloadditions, Metathesis

Zur Photochemie von 9‐Oxa‐tricyclo[4.2.1.0 ^2.5 ]nonadienen; Synthese von Derivaten des 9‐Oxa‐homokubans

Oxepine, III. Ein neuer Syntheseweg ausgehend von 2,5‐Cyclohexadien‐1,4‐diolen

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5‐Acetyl‐1,2,3,4,5‐pentamethyl‐bicyclo‐[2.1.0]penten

Cited by 6 publications

References 14 publications

Proximate,syn-Periplanar Diazene/Diazene(di)oxy, Diazeneoxy/Diazene(di)oxy, and Diazenedioxy/Diazenedioxy Skeletons: Syntheses, [2+2]Photocycloadditions, Metathesis

Proximate,syn-Periplanar Diazene/Diazene(di)oxy, Diazeneoxy/Diazene(di)oxy, and Diazenedioxy/Diazenedioxy Skeletons: Syntheses, [2+2]Photocycloadditions, Metathesis

Zur Photochemie von 9‐Oxa‐tricyclo[4.2.1.0 2.5 ]nonadienen; Synthese von Derivaten des 9‐Oxa‐homokubans

Oxepine, III. Ein neuer Syntheseweg ausgehend von 2,5‐Cyclohexadien‐1,4‐diolen

Contact Info

Product

Resources

About

Zur Photochemie von 9‐Oxa‐tricyclo[4.2.1.0 ^2.5 ]nonadienen; Synthese von Derivaten des 9‐Oxa‐homokubans