Photochemische Umwandlungen. XV [1] Photochemische Isomerisierung des exo-Tricyclo[4.2.1.02′5]nona-3,7-dien-Systems. Vorläufige Mitteilung

The acetone sensitized isomerization of two exo-tricyclo[4.2.1.0^2,5]nonadiene derivatives, of the corresponding tricyclo[4.3.0.0^2,5]nonadienes, and the photoisomerization of two bicyclo[4.3.0]nonatrienes by direct excitation are described.     

Photochemische Umwandlungen. XVIII Photochemische Isomerisierung annellierter Oxanorbornadiene Vorläufige Mitteilung

Photochemical cycloaddition reactions in anellated oxanorbornadiene derivatives have been investigated. In the case of 7a the tetracyclic isomer 8a can be isolated which adds dimethylacetylenedicarboxylate in the manner of a bis-homo-furan system. On thermal activation 8a yields the thiepino-oxepin derivative 9a. In contrast, on direct photoexcitation of the benzoxanorbornadiene the primary photoproduct cannot be identified, the reaction leading directly to the benz[d]oxepin.     

Photochemische Umwandlungen. XXVII [1]. Ein «stabiles» Benzoloxid Vorläufige Mitteilung

By thermal isomerization of the 3-oxa-6.7-diphenyl-tetracyclo [3.2.0.0^{2, 7}. 0^{4, 6}]-heptane-1. 5-dicarbomethoxylate (4) besides the oxanorbornadiene 3 and the hydroxy-fulvene 7, the ‘stable’ benzeneoxide 7-oxa-2.5-diphenyl-bicyclo [4.1.0] hepta-2.4-diene-3.4-dicarbomethoxylate (5) has been isolated. In the temperature range ?50 to 170°C no equilibration with the monocyclic oxepine 6 has been detected.     

Photochemische Umwandlungen, 41 [1] 3ω → 3 π-Isomerisierungen von Monohetero-trishomobenzol-derivaten. Vorläufige mitteilung

The all-cis-oxa- and azatrishomobenzene diesters 4a and 4b resp. undergo thermally a very clean 3ω → 3π isomerization reaction yielding the heterocyclonona-2, 5, 8-triene derivatives 6a and 6b resp. (E_a = 27.4 and 26.5 kcal/mole). In contrast, the cis, cis, trans-oxatrishomobenzene diester 9 is stable up to 170°. Some applications and limitations of this 3ω → 3π-route to iso- and heterocyclononatriene derivatives are discussed.     

Calicen Hochpolare Dicyan-diphenyl-derivate [1] [2]. Vorläufige Mitteilung

Three dicyano-diphenyl-calicenes have been synthesized. Judged by the dipole moments, the uv. and nmr. data, there is appreciable charge separation in the ground states.     

Thermisches Verhalten von Mesitylallenen; Beispiel einer aromatischen [1, 5s]-sigmatropischen H-Verschiebung. Vorläufige Mitteilung

Mesitylallene ( 6a ), 1-mesityl-3-methyl-allene ( 6b ) and 1-mesityl-3, 3-dimethylallene ( 6c ) were prepared via dienol-benzene-rearrangements. At 170° 6a isomerises to give 5, 7-dimethyl-1, 2-dihydronaphthalene ( 8 ). Under the same conditions 6b rearranges to give 2, 5, 7-trimethyl-1, 2-dihydronaphthalene ( 10 ; 60%) and cis-1-mesitylbuta-1, 3-diene ( 11 ; 40%) while 6c gives only cis-1-mesityl-3-methyl-buta-1, 3-diene ( 13 ). The allenes undergo first an aromatic [1, 5 s]-sigmatropic H-shift to the o-xylylene derivatives 7, 9 and 12 , which then exhibit disrotatory ring closure to the dihydronaphthalenes or aromatic [1, 7 a]-sigmatropic H-shift to the 1-mesitylbuta-1, 3-dienes.     

Photochemische Umwandlungen. XXXIV [1]. Photochemische Isomerisierung substituierter Benzonorbornadiene

The benzonorbornadiene derivatives 4 , 5 , 6 and 19 give upon direct photoexcitation the benzo-tricyclo [3.2.0.0^{2, 7}] heptenes 14 , 17 , 21 and 23 in yields up to 60%. Sensitization by acetone improves the yields considerably. The spectral data of the substrates 4 , 5 , 6 , 7 and 19 , of the photoproducts 14 , 17 , 21 and 23 , as well as of the dihydrobenzonorbornadienes 13 , 16 and 22 , are presented.     

Cycloaddition an das Tetracyclo[4.2.0.02, 8.05, 7]octan-System [1]. Vorläufige Mitteilung

The tetracyclo [4.2.0.0^{2, 8}.0^{5, 7}]octane derivative 2 adds dienophiles (tetracyanoethylene, dimethylacetylenedicarboxylate) stereospecifically to its bishomocyclobutadiene system, yielding the adducts 5 and 6 , resp.     

Photochemische Umwandlungen,XXXVII [1]. Synthese von Methylen-tetracyclo[3.2.0.02,7.04,6]heptan-Derivaten

Several isopropylidene-, benzylidene- and benzhydrylidene-norbornadiene derivatives ( 11 , 16 ) have been synthesized. The [2π+2π] cycloadditions leading to the tetracyclic isomers 12 and 17 resp. upon direct photoexcitation proceed practically quantitatively in the case of the trienes 11 , much less specifically, however, with 16 . Sensitization by acetone or fluorenone allows the isolation of the quadricyclanes 17 in 20–90% yields.     

Photochemische Cycloadditionen von 3-Phenyl-2H-azirinen mit kumulierten Doppelbindungen. Vorläufige Mitteilung

Irradiation of 2-methyl- ( 1c ) and 2,2-dimethyl-3-phenyl-2H-azirine ( 1d ) in benzene solution in the presence of carbon dioxide yields 2-methyl-4-phenyl- ( 3c ) and 2,2-dimethyl-4-phenyl-3-oxazolin-5-one ( 3d ), respectively. Similar cycloadducts are observed (see table) when 2,3-diphenyl-2H-azirine ( 1b ) and 1d are irradiated in the presence of phenylisocyanate, o-tolylisocyanate, phenylisothiocyanate or di-o-tolyl-carbodiimide.     

Photochemische Cycloadditionen von 3-Phenyl-2H-azirinen mit aktivierten Doppelbindungen. Vorläufige Mitteilung

Irradiation of 2-methyl- ( 1a ), 2,2-dimethyl- ( 1b ) and 2,3-diphenyl-2H-azirine ( 1c ) in the presence of diethyl mesoxalate yields the corresponding 4-phenyl-5,5-diethoxycarbonyl-3- oxazolines 3a–c . Similar cycloadducts are observed (cf. 6 ) by irradiation of 1b and 1c in the presence of trifluoroacetophenone. When ethyl cyanoformate is used as trapping agent photolysis of 1b or 1c leads to cycloadducts with the carbonyl and nitrile group, respectively which are present in the cyanoformate.     

1, 6-Addition von Chlorsulfonylisocyanat. Vorläufige Mitteilung

A 1, 6-addition of sulfonyl chloride isocyanate to 5, 7-dimethyl-8-methylidene-tricyclo[3.2.1.0^2,7]oct-3-en-6-one ( 1 ) produced the new tricyclic skeleton of 4a, 6-dimethyl-2, 5-dioxo-2, 3, 4a, 5, 6, 8a-hexahydro-1H-6, 4-methenoquinoline-1-sulfonyl chloride ( 2 ). The structure of the new aza-tricyclic species has been elucidated by X-ray analysis.     

Thermisches Verhalten von o-Dipropenylbenzol,Beispiel einer aromatischen [1,7]-sigmatropischen H-Verschiebung. Vorläufige Mitteilung

cis, cis-, cis, trans- and trans, trans-o-Dipropenylbenzene (cis, cis-, cis, trans- and trans, trans- 1 ) were prepared. At 225° cis, cis- 1 isomerises to give cis, trans- 1 and vice versa. The isomerisation follows 1. order kinetics. At equilibrium 89% cis, trans- and 11% cis, cis- 1 are present. It is shown by deuterium labelling that the isomerisation is due to aromatic [1, 7 a] sigmatropic H-shifts. trans, trans- 1 rearranges at 225° to yield 2, 3-dimethyl-1, 2-dihydronaphthalene ( 3 ). This can be visualized by disrotatory ring closure of trans, trans- 1 followed by an aromatic [1, 5 s] H-shift. When cis, cis- or cis, trans- 1 are heated for 153 hrs at 225° a small amount (3%) of 1-ethyl-1,2-dihydronaphthalene ( 5 ) is formed.     

Photochemische Umwandlungen. XXXVIII [1]. Synthese und Eigenschaften Methoxycarbonyl-substituierter «Quadricyclanone»

The three methoxycarbonyl-substituted quadricyclanones 7a , 7b and 7c have been synthesized in good to excellent yields. Some of their physical (UV., NMR.) and chemical properties (e.g. condensation and pyrolysis reactions) are discussed.     

Photoelektronspektroskopische Bestimmung der Wechselwirkung zwischen nicht-konjugierten Doppelbindungen [1]. Vorläufige Mitteilung

The interaction between the two non-conjugated π-bonds in 1, 4-cyclohexadiene, norbornadiene and bicyclo[2.2.2]octadiene has been determined by photoelectron spectroscopy to be 1.0, 0.8₅ and 0.6 eV respectively.     

Synthese von 1α-Hydroxycholecalciferol. Vorläufige Mitteilung

1α-hydroxycholesterol ( 4a ) was synthesized from cholesterol and transformed via its diacetyl derivative 4b into 1α, 3β-diacetoxycholesta-5, 7-diene ( 6b ). Irradiation of the ring-B-diene 6b followed by thermal isomerization and saponification gave 1α-hydroxycholecalciferol ( 7 ).