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

Bei direkter und sensibilisierter (Aceton, Benzophenon) Anregung werden die 5‐Benzhydryliden‐ bzw. 5‐Benzylidentetracyclo[4.3.0.02,4.03,7]non‐8‐en‐ester 11a–f bzw. 22, 24 in guten bis sehr guten Ausbeuten zu den 5‐Benzhydryliden‐ bzw. 5‐Benzylidentricyclo[4.3.0.02,9]‐nona‐3,7‐dien‐estern 13a–f bzw. 23, 25 isomerisiert. Die 5‐Isopropylidenverbindungen 27a–d liefern bei direkter Anregung ein Gemisch der entsprechenden Tricyclen 28a–d und der 9‐Isopropylidenbicyclo[4.2.1]nona‐2,4,7‐trien‐ester 29a–d. Letztere werden bei der Sensibilisierung mit Aceton ausschließlich gebildet. Die Umlagerung Tetracyclo [4.3.0.02,4.03,7]‐non‐8‐en → Tricyclo[4.3.0.02,9]nona‐3,7‐dien kommt bei der direkten Belichtung des Spiro‐Analogen 34 neben Lösungsmitteladdition nur in bescheidenem Umfang zum Zuge. In keinem Fall wurde eine [2π + 2σ]‐Cycloaddition in nachweisbarem Ausmaß realisiert. Die spektroskopischen Daten sowie einige Umsetzungen der Photoprodukte (Thermolyse, Cycloadditionen) werden beschrieben.

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Photochemische Isomerisierungen im 5‐Methylentetracyclo[4.3.0.0 ^2,4 .0 ^3,7 ]non‐8‐en‐System

Prinzbach

Auge

Basbudak

1973

Chem. Ber.

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Die Photoreaktivität von geometrisch fixierten 1,5‐Dienen: Das exo ‐Tricyclo[4.2.1.0 ^2,5 ]nonadien‐System

Eberbach

1974

Chem. Ber.

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SystemThe preparation and photochemical behavior of the tricyclic 1,Sdienes 12a, b-15 are described. The main pathway in the photoreactions involvps formation of the respective isomers 25a, b, 35, 43 and 49 which -preferentially on sensitized irradiation or thermal activation -are converted to the bicyclic trienes 27a, b, 36,46 (only thermally) and 50. Additionally, photolysis of 12a.b-14 leads to dimeric products to which the structures 26a,b 34 and 44/45 -the result of head to head cycloaddition between the cyclobutene C=C-double bonds -are tentatively assigned on the basis of spectroscopic data and soma chemical evidence obtained in the case of 34. Irradiation of the diphenyl-tetraester 15 produces 49 as the major compound and the endo-diene 51 as a second primary photoisomer which subsequently undergoes cyclization to the homocubane 52. However, 52 is photochemically instable, too, and decomposes in a novel fragmentation reaction affording 1,2,3,4-tetramethoxycarbonylbenzene (53) and the -not directly observed -1,2-diphenylcyclopropene (74) which reacts to the actually isolated 1,2,4,5-tetraphenylbenzene (54). The phototransformations obtained with the 1,5-dienes 12a,b--15 proceed much faster in the sensitized runs than on direct excitation andwith the exception of 15 -give rise to a more favorable mass balance. No definite conclusions

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Synthese, Thermolyse und Photolyse substituierter 3,4‐Epoxy‐cycloalkene

Eberbach

Carré

1981

Chem. Ber.

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Synthesis, Thermolysis, and Photolysis of Substituted 3,4-Epoxy-cycloalkenes1)The substituted epoxy-cycloalkenes 5-7 are transformed thermally at 200-250'C into the benzene derivatives 10, 15, and 18 after initial C/O-bond cleavage of the oxirane ring. At temperatures higher than 300°C (short time pyrolysis) 6 and 7 give, in addition to the aromatic compounds 15/18, the furans 16 and 19, respectively. On photochemical excitation 5 -7 react with C/C-ring opening to the annelated 2,3-dihydrofurans 11, 17, and 20, respectively. The epoxycycloheptene 8 undergoes analogous ring expansion leading to 21 on electronic as well as thermal activation (ca. 80% yield). Whereas 21 does not form any defined product up to 380°C. and the monosubstituted bicyclus 11 suffers fragmentation affording methyl 3-furancarboxylate (12) and ethylene, both dihydrofurans 17 and 20 are quantitatively converted back into the epoxy-cycloalkenes 6 and 7, respectively, at temperatures below 200°C; the cycloreversion reaction affording 16/19 competes only above 300°C. The cyclic dipoles of type IV, assumed to occur as intermediates during !he 2,3-dihydrofuran-vinyloxirane isomerisations 17 .6/20 .7, can be trapped with dimethyl acetylenedicarboxylate or N-phenylmaleimide at significantly lower temperature (15O/12O0C) to give the 1 : 1-cycloadducts 38-40. However, because no such products could be obtained in case of the photoreactions of 5 -8, a concerted [ I ,3]-C-migration has to be considered as a mechanistic alternative of the light-induced formation of 11, 17, 20, and 21.

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

Cited by 9 publications

References 46 publications

Photochemische Isomerisierungen im 5‐Methylentetracyclo[4.3.0.0 ^2,4 .0 ^3,7 ]non‐8‐en‐System

Photochemische Isomerisierungen im 5‐Methylentetracyclo[4.3.0.0 ^2,4 .0 ^3,7 ]non‐8‐en‐System

Die Photoreaktivität von geometrisch fixierten 1,5‐Dienen: Das exo ‐Tricyclo[4.2.1.0 ^2,5 ]nonadien‐System

Synthese, Thermolyse und Photolyse substituierter 3,4‐Epoxy‐cycloalkene

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

Cited by 9 publications

References 46 publications

Photochemische Isomerisierungen im 5‐Methylentetracyclo[4.3.0.0 2,4 .0 3,7 ]non‐8‐en‐System

Photochemische Isomerisierungen im 5‐Methylentetracyclo[4.3.0.0 2,4 .0 3,7 ]non‐8‐en‐System

Die Photoreaktivität von geometrisch fixierten 1,5‐Dienen: Das exo ‐Tricyclo[4.2.1.0 2,5 ]nonadien‐System

Synthese, Thermolyse und Photolyse substituierter 3,4‐Epoxy‐cycloalkene

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Product

Resources

About

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

Photochemische Isomerisierungen im 5‐Methylentetracyclo[4.3.0.0 ^2,4 .0 ^3,7 ]non‐8‐en‐System

Photochemische Isomerisierungen im 5‐Methylentetracyclo[4.3.0.0 ^2,4 .0 ^3,7 ]non‐8‐en‐System

Die Photoreaktivität von geometrisch fixierten 1,5‐Dienen: Das exo ‐Tricyclo[4.2.1.0 ^2,5 ]nonadien‐System