Efficient photolytic esterification of carboxylic acids with alcohols in perhalogenated methane

Condensation of carboxylic acids and alcohols to give esters was accomplished with selectivity under photolytic conditions in 66-99% yields by use of CCl₄ or BrCCl₃ at room temperature.     

Photodegradation of some 14,15-bisnorlabdene-13-ones, derived from larixol. Synthesis of drimanic dienes with functional groups at C-6

Valuable chiral drimanic dienic synthons have been prepared by a photolytic Norrish type II degradation of the corresponding 14,15-bisnorlabdene-13-ones. Minor by-products with unexpected bi- and tricyclic structures were formed and some of them were isolated and identified.     

Influence of the β-substitution on the photochemistry of α,2-diacetoxystyrenes. Irradiation of phenyl,vinyl, and benzyl derivatives

Summary -Substitution shows a pronounced influence on the photochemistry of ,2-diacetoxystyrenes. As in the case of the parent compound, intramolecular cyclization with participation of the neighbouring 2-acetoxy group takes place upon irradiation of the enol esters4a–c; however other processes are also observed, depending on the substrate. The phenyl derivative4a gives theE isomer7a and the phenanthrene9. The vinyl derivative4b also undergoescis-trans isomerization and/or photooxidation, to afford7b and10. Finally, a 1,4-acyl migration occurs in the benzyl derivative4c, whereby the 1,4-diketone12 is formed.

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Einfluß der -Substitution auf die Photochemie von ,2-Diacetoxystyrolen. Bestrahlung von Phenyl-, Vinyl- und Benzylderivaten

Zusammenfassung Bei ,2-Diacetoxystyrolen haben die -Substituenten einen deutlichen Einfluß auf das photochemische Verhalten. Wie im Fall der Stammverbindung erfolgt bei der Bestrahlung der Enolester4a–c intramoleukulare Cyclisierung unter Einbeziehung der benachbarten 2-Acetoxygruppe; jedoch werden je nach Substrat auch andere Reaktionen beobachtet. Das Phenylderivat4a liefert dasE-Isomer7a und das Phenanthren9. Das Vinylderivat4b erfährt ebenfallscis/trans-Isomerisierung zu7b und/oder Photooxidation zu10. Beim Benzylderivat4c tritt eine 1,4-Acylverschiebung zum 1,4-Diketon12 auf.

     

Pyrolysis and photolysis processes of pyran and thiopyran derivatives

Summary Pyrolysis and photolysis of 2-amino-3,5-dicyano-6-phenyl-4H-pyran (1) afford HNCO, acrylonitrile, cinnamonitrile, and 2-hydroxy-3,5-dicyano-6-phenylpyridine. Pyrolysis of 2-carboxyimino-3,5-dicyano-6-phenyl-4H-pyran (2) gives HCN, acrylonitrile, cinnamonitrile and 2-hydroxy-3,5-dicyano-6-phenylpyridine. Furthermore, both pyrolysis and photolysis of 2,6-diamino-3,5-dicyanothiopyran (3a) gives rise to HNCS, acrylonitrile and 6-amino-3,5-dicyano-6-mercaptopyridin. Moreover, comparative studies of pyrolysis and photolysis of 2,6-dicyano-4-arylthiopyran derivatives3b–d revealed similar results. The similarity of products obtained from pyrolysis and photolysis and the mechanistic implications of these data are discussed.

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Pyrolyse- und Photolyseprozesse von Pyran- und Thiopyranderivaten

Zusammenfassung Pyrolyse und Photolyse von 2-Amino-3,5-dicyano-6-phenyl-4H-pyran (1) ergeben HNCO, Acrylnitril, Zimtsäurenitril und 2-Hydroxy-3,5-dicyano-6-phenyl pyridin. Durch Pyrolyse von 2-Carboximino-3,5-dicyano-6-phenyl-4H-pyran (2) entstehen HCN, Acrylnitril, Zimtsäurenitril und 2-Hydroxy-3,5-dicyano-6-phenylpyridin. Weiters resultieren sowohl Photolyse als auch Pyrolyse von 2,6-Diamino-3,5-dicyanithiopyran (3a) in der Bildung von HNCS, Acrylnitril und 6-Amino-3,5-dicyano-6-mercaptopyridin. Vergleichende Untersuchungen zur Pyrolyse und Photolyse von 2,6-Dicyano-4-arylthiopyranderivaten (3b–d) lieferten vergleichbare Ergebnisse. Die Ähnlichkeit der Resultate von Pyrolyse und Photolyse sowie die sich daraus ergebenden mechanistischen Implikationen werden diskutiert.

     

ClONO2及其异构体光解反应的从头算研究(Ⅱ)——ClONO2→ClO+NO2反应机理研究

用从头算方法讨论了大气臭氧层主要破坏物ClONO2在光照下分解反应途径:ClONO2→ClO+NO2的反应机理.该反应的2个过渡态ClO…NOO(TS2a)和OCI…NOO(TS2b)中TS2a能垒较高,始态难于越过如此高的势垒;TS2b势垒较低,而产物到过渡态TS2b的能垒也仅有1.20 eV,故预测该反应为一个可逆反应.     

Micelle formation induced by photolysis of a poly(<Emphasis Type="Italic">tert</Emphasis>-butoxystyrene)-<Emphasis Type="Italic">block</Emphasis>-polystyrene diblock copolymer

We found the novel photolysis-induced micellization of the poly(tert-butoxystyrene)-block-polystyrene diblock copolymer (PBSt-b-PSt). PBSt-b-PSt with a molecular weight of Mn(PBSt-b-PSt) = 15,000-b-97,000 showed no self-assembly in dichloromethane and existed as isolated copolymers with a hydrodynamic diameter of 16.6 nm. Dynamic light scattering demonstrated that the copolymer produced micelles with a 63.0 nm hydrodynamic diameter when the copolymer solution was irradiated with a high-pressure mercury lamp at room temperature in the presence of bis(alkylphenyl) iodonium hexafluorophosphate, a photoacid generator. The ¹H NMR analysis revealed that the micellization resulted from the photolysis of the PBSt blocks into insoluble poly(vinyl phenol) blocks based on the fact that the signal intensity of the tert-butyl protons decreased over time during the irradiation. It was found that the micellization rapidly proceeded as the degree of the photolysis reached over 50% and was completed at 90%.     

乙酰基的电子激发态

对乙酰基的基态（X12A′）和激发态进行了理论和实验研究。通过采用MRSDCI和MP2方法计算，获得了CH3CO自由基的四个电子激发态（A12A″，B22A′，C32A′，D22A″），其垂直激发能分别为250．8kJ·mol－1，472．3kJ·mol－1，645．8kJ·mol－1和674．7kJ·mol－1。运用时间分辨付里叶红外光谱仪（TR－FTIR）分别研究了CH3CO自由基的热解和光解反应，观察到初生产物CO（V）的红外发射光谱．势垒仅为75．2kJ·mol－1的基态CH3CO极易热解．532um的激光只能将CH3CO激发到束缚态A12A″，故未观察到CO信号；而248nm或266nm的激光可使CH3CO发生B22A′←X12A′跃迁，生成高振动激发的CO（V8）产物．     

Synthesis of pyrrolo[2,3-d]pyrimidine-2,4-diones by sunlight photolysis of N-(5-vinyluracil-6-yl)sulfilimines

Uracil derivatives having a vinyl group at the C-5 position and a sulfilimine moiety at the C-6 position were prepared and cyclized to 1,3,6-trisubstituted pyrrolo[2,3-d]pyrimidine-2,4-diones by sunlight photolysis in good yields.     

Mechanistic Studies on the Photogenerated Dienol with α-Phenyl-N-tert-Butylnitrones

The mechanism for the photochemical reactions of o-methyl-benzaldehyde ( 1 ), o-methyl-acetophenone ( 2 ) and o-methyl-benzophenone ( 3 ) in the presence of α-phenyl-N-tert-butylnitrone (PBN) to the formation of stable nitroxyl radicals 4–6 is studied. The nitroxyl radical product 6 can also be obtained by the thermolysis of benzocyclobutenol with PBN. Thus, the radical products were derived from a novel and regioselective 4+2 cycloaddition of the photogenerated dienol intermediate with PBN.     

Eine einfache Synthese von 11H-Indolo[3,2-c]chinolin-6-onen

11H-Indolo[3,2-c]quinolin-6-ones, which are containing the -carboline ring system, can be easily synthesized from 4-azido-3-phenyl-2(1H)-quinolones, which are obtained in a two step reaction from 4-hydroxy-3-phenyl-2(1H)-quinolones. Cyclization of the azides can be realized by irradiation or thermal reaction.