92756-84-8Relevant academic research and scientific papers
THE PHOTOCHEMICAL NUCLEOPHILE-OLEFIN COMBINATION, AROMATIC SUBSTITUTION REACTION (PART 2): METHANOL-CYCLIC OLEFINS, 1,4-DICYANOBENZENE
Arnold, Donald R.,Snow, Miles S.
, p. 3012 - 3026 (2007/10/02)
Direct irradiation of acetonitrile-methanol (3:1) 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 1:1:1 (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 1-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 1H and 13C 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.
Radical ions in photochemistry, 15. The photosubstitution reaction between dicyanobenzenes and alkyl olefins
Borg, Robert M.,Arnold, Donald R.,Cameron, T. Stanley
, p. 1785 - 1802 (2007/10/02)
The photosubstitution (electron transfer) reaction between 1,4-dicyanobenzene (1) and 2,3-dimethyl-2-butene (2), which gives 1-(4-cyanophenyl)-2,3-dimethyl-2-butene (3) and 3-(4-cyanophenyl)-2,3-dimethyl-1-butene (4), has been extended to other dicyanobenzene-olefin mixtures.Substitution of cyano group occurs when both 1 or 1,2-dicyanobenzene (5) are irradiated in acetonitrile solution, in the presence of 2 or cyclohexane (16).Under comparable conditions 1,3-dicyanobenzene (6) failed to react.Little or no substitution was observed in any case when the olefin was methylpropene (19).The results for 1 and 5 are in agreement with empirical free energy calculations (Weller equation) for the electron transfer process which, howover, fail to explain the general lack of reactivity of 1,3-dicyanobenzene.Phenanthrene (11) has been shown to photosensitize the photosubstitution reaction between dicyanobenzenes and 2.Under these conditions the olefin reacts with 6 predominantly at the 4-position, resulting in overall substitution of a hydrogen atom.This reaction occurs regiospecifically, resulting in the formation of only one of the two possible isomeric side chains.The mechanistic details of these reactions have been substantiated by means of deuterium labelling studies.The aromatic nitriles also undergo photosubstitution by 2, in acetonitrile-methanol solution, resulting in methanol-incorporated products.Whereas reaction with 1 or 5 results in substitution of a cyano group, 6 was observed to give isomeric dicyanocyclohexenes, resulting from initial reaction at the 4-position, followed by reduction.A detailed mechanism for this secondary photoreduction has been substantiated by deuterium labelling studies.The anomalous behaviour of 1,3-dicyanobenzene has been attributed to a difference in the reactivity of the radical anion.
