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Direct irradiation of acetonitrile-methanol (3:l) solutions of 1,4-dicyanobenzene and the cyclic olefins, cyclohexene, 1-methylcyclohexene, norbornene, and 2-methylnorbornene, leads to formation of regio-and stereoisomers of the 1:l:l (alcohol:olefin:aromatic) adducts. This reaction can be photosensitized by electron transfer; addition of electron donors, biphenyl or phenanthrene, to the irradiation mixture generally increases the efficiency and yield of adduct formation. The efficiency of the reaction and the ratio of isomeric adducts are also affected by the addition of salts, particularly magnesium perchlorate. All of the possible regio-and stereoisomers from cyclohexene and I -methylcyclohexene have been identified, two from cyclohexene and four from 1-methylcyclohexene. Three of the four possible isomers from norbornene were characterized; the endo,endo isomer was not detected. There are eight possible isomers from 2-methylnorbornene; six were detected and five have been isolated and identified. The two sterically hindered isomers, those having both the 4-cyanophenyl and the methoxy groups in the endo position, and exo-3-(4-cyanophenyl)-endo-2-methoxy-exo-2-methylnorbornane, were not characterized. The structures of the products were established largely on the basis of the 'H and I3C nuclear magnetic resonance spectra. The mechanism of the reaction is discussed, with emphasis on those factors that may affect the product ratio. The most striking observation is that the reaction is regioselective when magnesium perchlorate is added to the irradiation mixture.

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150 (1985). The electron spin resonance (esr) spectra of eighteen para-substituted cumyl radicals were analyzed. The relationship between the P-hyperfine coupling (P-hfc) constants of these cumyl radicals and the corresponding a-hfc constants of benzyl radicals was studied. Although there is a general trend for the a -and P-hfc values to vary in a similar manner, specific deviations from a linear correlation between these parameters were observed. These deviations were rationalized by considering charge effects on spin delocalization. The correlation coefficient for the linear regression analysis of these a -and P-hfc values was found to significantly improve when parameters reflecting charge effects on spin delocalization were included in an extended Hammett treatment of the spectral data. DONALD R. ARNOLD, A. MARTIN DE P. NICHOLAS et MILES S. SNOW. Can. J. Chem. 63, 1150Chem. 63, (1985. On a analysC les spectres de rCsonance paramagnktique Clectronique (rpe) de dix-huit radicaux cumyles substituCs en position para. On a ttudiC la relation existant entre la constante de couplage hyperfin-p (chf-P) de ces radicaux cumyles et les constantes chf-a correspondantes des radicaux benzyles. Les valeurs des chf-a et chf-P tendent gCnCralement a varier de la m&me faqon: cependant on observe des dkviations spkcifiques par rapport a la corrklation IinCaire entre ces paramktres. On rationalise ces Ccarts en considkrant les effets de la charge sur la dtlocalisation du spin. On a trouvC, que pour ces valeurs de chf-a et chf-P, le coefficient de corrklation de l'analyse de rCpression IinCaire est amCliorC d'une faqon significative lorsque les paramktres qui reflktent les effets de la charge sur la dtlocalisation de spin sout inclus dans un traitement de Hammett Clargi des donnCes spectrales.[Traduit par le journal]

Solutions of (I)‐(VIII) and the photosensitizer 1,4‐dicyanobenzene in MeOH‐MeCN (1:3) are degassed and then irradiated through a Pyrex filter using a medium‐pressure mercury lamp, usually at 10 and 80 °C. Only (I), (II), (VII), and (VIII) give Ph2CH2 + an ether or acetal such as Me‐O‐CH2‐O‐Me in the case of (VIII).