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New heteroaryl‐substituted o‐divinylbenzenes, 2,2′‐(1,2‐phenylenedivinylene)difuran (9), 2,2′‐(1,2‐phenylenedivinylene)bisbenzo[b]furan (10), and 2,2′‐(1,2‐phenylenedivinylene)bisnaphtho[2,1‐b]furan (11), were prepared and irradiated at various concentrations; intramolecular photocycloaddition and intermolecular [2+2] twofold photoaddition reactions took place to give bicyclo[3.2.1]octadiene derivatives 12–14and cyclophane derivatives 15–17, respectively. Compound 11was the most selective of these o‐divinylbenzenes, which, owing to π–π intra‐ or intermolecular complexation, gave only the exo‐bicyclo[3.2.1]octadiene derivative 14at low concentrations, and only the cyclophane derivative 17at high concentrations.

The photochemistry of 2,2′-(1,2-phenylenedivinylene)dipyrroles (4a,b) has been investigated under various conditions. After excitation of the starting material, an electron transfer followed by hydrogen transfer and radical combination occurs giving 2-{[1-(2H-pyrrol-2-ylidene)methinyl]-2-indanyl}pyrrole (14) as the intermediate. The intermediate could not be isolated, but trapped by nucleophiles, like methanol and diethylamine, giving as addition products, new functionalised indanylpyrroles (9). Irradiation of 4ain the presence of triethylamine afforded the indanylidene-pyrroles 8.

Ramber-Bäcklund rearrangement of disulfone 2leads to the ring-contracted 4,6:11,13-di(1,3-adamantano)cyclotetradeca- trans, trans-1,8-diene ( 3a) along with 4,6:11,13-di(1,3-adamantano)cyclotetradeca- cis, trans-1,8-diene ( 3b) and 4,6:12,14-di(1,3-adamantano)-8,10-dehydro-9,9-dichlorocyclopentadeca-1-diene ( 4) as a minor products. The ring inversion of 3acan most reasonably be interpreted in terms of equilibrium process between two conformers with effective C 2hsymmetry.

AbstractOne of the major product from the photodimerization of 2-[2-(2-methyl-phenyl)ethenyl)]naphtho[2. 1-b]furan (1) is a new fused cyclobutane-naphthofuran derivative, 6-(2-methylphenyl)-1-[2-(2-methylphenyl)ethenyl]-7-(2-naphtho-[2,1-b]furyl)-3-[2,1]naphtho-2-oxabicyclo[3.2.0]hept-3-ene (2). Its 1H and 13C NMR spectra were fully assigned by the application of COSY, LR COSY, NOESY, APT and HETCOR experiments in deuterated chloroform, acetone and benzene solutions.

New photochemically induced intramolecular cycloaddition and double cycloaddition of 5,5′-dimethyl-2,2′-(o-phenylenedivinylene)dipyrrole (4b) led to the formation of 2-{[2-(5-methyl-2-pyrrolyl)indan-1-ylidene]methinyl}-5-methylpyrrole (8) and 2-methyl-9-(5-methyl-2-pyrrolyl)-3b,4,8b,9-tetrahydro-4,5-benzopentaleno[1,2-b]pyrrole (9), respectively, in a 1:1 ratio. The compounds were characterized spectroscopically. Under the same conditions 5-methyl-2-(2-vinylphenylethenyl)pyrrole (1c) undergoes only cis–transisomerization and decomposition.