[DO NOT ALTER/DELETE THIS TEXT]Irradiation of substituted 2-benzylidenecyclopentanone O-alkyl and O-acetyloximes in methanol provides a convenient synthesis of alkyl, alkoxy, hydroxy, acetoxy, amino, dimethylamino and benzo substituted annulated quinolines. paraSubstituents yield 6-substituted-2,3-dihydro-1H-cyclopenta[b]quinolines with 8-substituted products being obtained from ortho-substituted starting materials. Reactions of meta-substituted precursors are highly regioselective, with alkyl substituents leading to 5-substituted 2,3-dihydro-1H-cyclopenta [b]quinolines and more strongly electron-donating substituents generally resulting in 7-substituted products. 2-Furylmethylene and 2-thienylmethylene analogues yield annulated furo-and thieno-[2,3e]pyridines respectively. Sequential E-to Z-benzylidene group isomerisation and six π-electron cyclisation steps result in formation of a short-lived dihydroquinoline intermediate which spontaneously aromatises by elimination of an alcohol or acetic acid. For 2-benzylidenecyclopentanone Oallyloxime, singlet excited states are involved in both steps.

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The photochemical reactions of styrene, (E)-stilbene, phenylethyne, and diphenylethyne with pyrrole and N-methylpyrrole have been investigated. The pyrroles quench the fluorescence of the phenylethenes and phenylethynes efficiently and broad structureless emissions attributed to exciplexes are observed from the N-methylpyrrole systems. Substituted pyrroles (1:l and 2:l adducts) are formed from irradiation of the phenylethenes with pyrrole, and 2-styrylpyrroles result from the phenylethynes. Styrene, but none of the other arenes, undergoes photoaddition to N-methylpyrrole in the presence of 10 % acetic acid.

The Photoaddition of Pyrroles to Arylethenes and Arylethynes. -Pyrrole and N-methylpyrrole efficiently quenched the fluorescence of the arylethenes and arylethynes. Substituted pyrroles (1:1 and 2:1 adducts) are formed from irradiation of the phenylethenes with pyrrole, and 2-styrylpyrroles result from the phenylethynes. Data for the quenching of the fluorescence are presented. -(AUSTIN, M.; COVELL, C.; GILBERT, A.; HENDRICKX, R.; Liebigs Ann./Recl. (1997) 5, 943-946; Dep. Chem., Univ. Reading, Whiteknights, Reading, Berkshire RG6 2AD, UK; EN)

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