New Polycyclic Compounds from Photochemical Rearrangements of Some Substituted 2-Azatricyclo[5.2.2.01,5]undeca-4,8,10-trien-3-ones

The products formed on UV irradiation of several tricyclic compounds (i.e. 3 , 6 , 8 , 15 , and 17 , Schemes 2-4) were studied in detail. A marked dependence of the reaction course on the type and site of substitution was found. Among the several light-induced transformations, a novel rearrangement, i.e. 11 to 9 (Scheme 3) was identified. The formation of the polycyclic compound 13 on irradiation of 8a (Scheme 3) resulted from an unexpected skeletal rearrangement with dearomatization of one benzene ring. The structures of compounds 10 , 11 , and 13 were established by X-ray crystallography (Figs. 1-3). An attempt was made to give a general mechanistic picture of all observed photochemical results (Schemes 4-6).     

A Photochemical Route to 2-Substituted Benzo[b]furans

2-Substituted benzo[b]furans were synthesized by a one-step metal-free photochemical reaction between 2-chlorophenol derivatives and terminal alkynes by tandem formation of an aryl-C and a C-O bond via an aryl cation intermediate. The mild conditions and the application to chlorophenols rather of the more expensive bromo or iodo analogues makes this procedure environmentally convenient.     

Regiospecific Photochemical Synthesis of Methylchrysenes

Methylated polycyclic aromatic hydrocarbons (PAHs) are suspected to be some of the toxic compounds in crude oil towards marine life and are needed as single compounds for environmental studies. 1-, 3- and 6-methylchrysene (3a,b,c) were prepared as single isomers by photochemical cyclization of the corresponding stilbenoids in the Mallory reaction using stoichiometric amounts of iodine in 82-88% yield. 2-methylchrysene (3d) was prepared by photochemical cyclization where the regioselectivity was controlled by elimination of an ortho-methoxy group under acidic oxygen free conditions in 72% yield. These conditions failed to form 4-methylchrysene from the corresponding stilbenoid. All stilbenoids were made from a common naphthyl Wittig salt and suitably substituted benzaldehydes. We have also demonstrated that methylchrysenes can be oxidized to the corresponding chrysenecarboxylic acids by KMnO₄ in modest yields.     

Synthesis of Tricyclo [6.2.1.01,5]undecadiones via Intramolecular Photoaddition of 5-(1-Cyclopentenylmethyl)-3-alkoxy-2-cyclopentenones

Irradiation of the dienone methyl ether 3a furnished the unstable regioisomeric photoadducts 4a and 5a which on Lewis acid-catalyzed fragmentation afforded the tricyclic diketones 6,7 and 8 . The same mixture was obtained from the isobutyl ether 3b (Scheme 2).     

Rearrangement of 2,2′-dipropionylazoxybenzenes to 3-[1-alkoxy-1-(2-propionylarylamino)ethyl]benzo[c]isoxazoles

2,2-Dipropionylazoxybenzenes undergo rearrangement to the corresponding 3-[1-alkoxy-1-(2-propionylarylamino)ethyl]benzo[c]isoxazoles in the case of base catalysis; this transformation is realized only in the case of ortho,ortho' orientation of the propionyl groups in the substrate molecule and with the participation of the solvent as a reagent. A mechanism for the rearrangement that assumed the participation of one of the propionyl groups in intramolecular reduction of the azoxy group to an azo group is proposed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 743–748, June, 1983.     

Photochemical [3 + 2] cycloaddition of 2-cyanochromone to olefins

Irradiation of 2-cyanochromone in the presence of olefins gave rise to [3 + 2] cycloadducts together with the formation of normal [2 + 2] cycloadducts with the product ratio being temperature-dependent. The mechanism involving a vinyl nitrene intermediate was proposed.     

Photochemical Rearrangement of a Steroidal α, β-Epoxylactam. Photochemical reactions,XII [1]

The UV. irradiation of 17β-hydroxy-4α, 5α-epoxy-2-azaandrostan-3-one ( 1 ) yields 17β-hydroxy-2-aza-10 (5 → 4-abeo)-4ζ (H)-androsta-3,5-dione ( 3 ).     

聚苯乙烯基吡啶甲基氧乙烯醚的光化学性质

通过亲核取代反应将苯乙烯基吡啶功能基引入到聚氯甲基氧乙烯醚侧链上,制备出具有聚氧乙烯醚骨架的含有苯乙烯基吡啶盐功能基的线形光功能聚合物,该聚合物具有良好的水溶性.系统研究了上述光功能聚合物以及小分子参比物一氯化-N-丁基苯乙烯基吡啶盐的水溶液在不同紫外光照射下的光化学性质,发现参比物在长波紫外光(波长以365 nm为主)照射下只发生反-顺异构化,而所合成的光功能聚合物在同样紫外光照射下不仅能够发生反-顺异构化,而且能够发生功能基之间的光环加成反应.研究还发现,已经过照射发生光环加成反应的产物,在短波紫外光(波长为254 nm)照射下还可以发生快速光解开环反应.     

Photochemical Rearrangement of a Steroidal α,β-Epoxylactone. Photochemical reactions,XI [1]

The UV. irradiation of 17β-acetoxy-4α, 5α-epoxy-2-oxaandrostan-3-one ( 7 ) yields 17β-acetoxy-2-oxa-10(5 → 4)abeo-4ζ (H)-androsta-3,5-dione ( 11 ). A non-photochemical synthesis of 11 , proceeding in lower yield, is also described.     

A Photochemical Macrocyclization Route to Asymmetric Strained [3.2] Paracyclophanes

The intricate frameworks of paracyclophanes are an important target for synthesis since they are found in various chiral auxiliaries, solar cells, high-performance plastics, pharmaceuticals, and molecular machines. Whereas numerous methods exist for the preparation of symmetric paracyclophanes, protocols for the efficient synthesis of strained asymmetric scaffolds are limited. Here we report a remarkably simple photochemical route to strained [3.2]paracyclophanes starting from readily available educts. By way of NMR and X-ray analyses, we discovered that UV-irradiation of an aromatic carboxylic ester tethered to a toluene moiety leads to the intramolecular formation of a new C−C bond, with loss of an alcohol. A systematic evaluation of the reaction conditions and substituents, as well as radical starter and triplet quenching experiments, point to a reaction mechanism involving an excited triplet state and hydrogen atom transfer. The new method proved to be robust and versatile enabling the synthesis of a range of cyclophanes with different substitutions, including an unusual diastereoisomer with two planar chiral centers, and thus proved to be a valuable addition to the synthetic toolbox.     

4,4’-[1,n-亚烷基双[(E)-2-(4-氧苯基)乙烯基]]双吡啶的光化学性质(英文)

通过E-[4-[2-（4-羟基苯基）乙烯基]吡啶与1,n-二溴烷烃亲核取代反应合成了4,4’-[1,n-亚烷基双[（E）-2-（4-氧苯基）乙烯基]]双吡啶[n=2（Ia）,3（Ib）,4（Ic）,6（Id）].用元素分析、红外、紫外和质子核磁共振谱鉴定了Ia-Id的结构.将Ia-Id的稀溶液用中压汞灯和低压汞灯交替照射,发现其分子内光环加成反应的存在,并且随着亚烷基碳链的延长,反应速度加快.研究还发现锌离子可以与毗陡环上氮原子发生螯合作用使分子内光环加成反应加快.本文化合物荧光很弱,在较高浓度下有较强分子间激基缔合物荧光.     

A Rational Approach to Crosslinking of Coordination Polymers Using the Photochemical [2+2] Cycloaddition Reaction

Summary: Polymerization as a result of photocrosslinking is one of the most versatile technologies for producing organic polymers. This article highlights the formation of crosslinking in metal coordination polymers in the solid‐state using a photochemical approach and its importance in material science. Past and current developments of solid‐state photochemical [2+2] cycloaddition in organic and inorganic systems relevant to the topic are reviewed. The challenges for the coordination chemist in utilising this rational approach to orient the coordination polymers and the scope of this work are delineated.

The CC‐containing molecules can be aligned by metal coordination bonds in such a way as to promote crosslinking by a photochemical [2+2] cycloaddition reaction.     

Novel Photochemical Rearrangement of Styrylfurans

A conrotatory photocyclization , a novel [1,9] hydrogen shift, and a lateral ring opening are involved in the rearrangement of a series of 2-(4-alkylstyryl)furans 1 to 5-(3-alkylbutadienyl)benzo[b]furans 2 in dichloromethane. These novel photochemical rearrangements occur with good yields of isolated products.     

The Adamantane Rearrangement of Tricyclo[4.2.2.01,5]decane to Tricyclo[5.3.0.04,8]decane

Regioselective generation of the C(2)-carbocation a of tricyclo[4.2.2.0^1,5]decane ( 1 ) by treatment of both corresponding epimeric alcohols 5 and 6 with BF₃ and trapping the rearranged tricyclo[5.3.0.0^4,8]decan-7-yl carbocation b with Et₃SiH as hydride-ion donor (ionic hydrogenation) gives the corresponding hydrocarbon 3 as sole product in almost quantitative yield. The latter is a known intermediate in the Lewis-acid-catalyzed rearrangement of 1 to adamantane ( 4 ).     

Sequential [2+2] Photocycloaddition and Rearrangement to Substituted Cyclopentanone. A formal Synthesis of Planococcyl Acetate

An extremely short synthesis of 2,2-dimethyl-3-hydroxymethyl cyclopentanone 2 (R¹ = R² = Me), an advanced intermediate in the synthesis of the pheromone planococcyl acetate 3, is described.     

Rearrangement of 2-[1(3h)-oxodihydrobenzo[c]furan-3-yl] quinuclidin-3-ones to tetrahydrobenzo[b]quinolizines. A novel synthesis of benzo[b]quinolizine ring systems.

A new two step synthesis of benzo[b]quinolizine ring systems via the rearrangement of 2-[1(3H)-oxodihydrobenzo[c]furan-3-yl] quinuclidin-3-ones is described.