Photochemical nucleophile olefin NOCAS reaction

The photochemical nucleophile-olefin combination aromatic substitution (photo-NOCAS) reaction received considerable attention from many groups not only because of its synthetic value because the yields of nucleophile-olefm-arene (1 1 1) adducts can be high but also because of interesting mechanistic details (Scheme 48). 

The photochemical nucleophile olefin combination, aromatic substitution (photo-NOCAS) reaction, formulated below for 2,3-dimethylbutene-methanol-p-dicyano-benzene, has some synthetic utility. The final step, loss of cyanide ion, is not shown. 

There has been a study of photo-induced intramolecular cyclization of some o-haloarylheterylamines which may lead to pyridof 1,2-a]benzimidazole derivatives.51 Several studies have been reported of photochemical nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reactions with fluoride,52 cyanide,53 or acetonitrile54 acting as the nucleophile, hi the example illustrated in Scheme 3,... 

In some cases the nucleophilic capture of a radical cation is followed by coupling with the radical anion (or possibly with the neutral acceptor), resulting ultimately in an aromatic substitution reaction. Thus, irradiation of 1,4-dicyanobenzene in acetonitrile-methanol (3 1) solution containing 2,3-dimethylbutene or several other olefins leads to capture of the olefin radical cation by methanol, followed by coupling of the resulting radical with the sensitizer radical anion. Loss of cyanide ion completes the net substitution reaction [144]. This photochemical nucleophile olefin combination, aromatic substitution (photo-NOCAS) reaction has shown synthetic utility (in spite of its awkward acronym). 

The photochemical Nucleophile-Olefin Combination, Aromatic Substitution (Photo-NOCAS) reaction, in Handbook of Organic Photochemistry and Photobiology, 2nd edn (eds W. Horspool and F. Lenci), CRC Press, Boca Raton, pp. 40-1-40-17. 

Arnold, D. R., Chan, M. S. W., McManus, K. A., Photochemical Nucleophile Olefin Combination, Aromatic Substitution (Photo NOCAS) Reaction. 12. Factors Controlling the Regiochemistry of the Reaction with Alcohol as the Nucleophile, Can. J. Chem. 1996, 74, 2143 2166. 

The scope of the photochemical nucleophile-olefin combination, aromatic substitution (photo-NOCAS) reaction has been extended to include cyanide. 

Some interesting photo-NOCAS-type reaction (photochemical nucleophile-olefin combination, aromatic substitution) have been reported by three groups. Arnold has developed the photo-NOCAS reaction as three components photoaddition.Xu et al., reported the intramolecular photocyclization of A-(co-hydroxyalkyl)-tetrachlorophthalimide (138, 141) with alkenes to give medium- and large-ring heterocycles (140,143). These photoreactions proceeded via 1, n-biradicals generated from the nucleophilic attack of alcohols to alkenes between the radical anions of phthalimides and the radical cations of alkenes. 

Arnold, D.R., McManus, K.A., and Du, X., Photochemical nucleophile- olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 6 methanol-nonconjugated dienes and 1,4-dicyanobenzene, Can. J. Chem., 72,415,1994. 

Mangion, D., Arnold, D.R., Cameron, T.S., and Robertson, K.N., The electron transfer photochemistry of allenes with cyanoarenes. Photochemical nucleophile—olefin combination, aromatic substitution (photo-NOCAS) and related reactions, /. Chem. Soc., Perkin Trans. 2, 48, 2001. 

The Photochemical Nucleophile-Olefin Combination, Aromatic Substitution (Photo-NOCAS) Reaction... 

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