Aryl cations from aromatic halides. Photogeneration and reactivity of 4-hydroxy(methoxy)phenyl cation.

摘要: The photochemistry of 4-chlorophenol (1) and 4-chloroanisole (2) has been examined in a range solvents found to lead mainly reductive dehalogenation, through homolytic path cyclohexane heterolytic alcohols. Heterolysis 1 2 methanol 2,2,2-trifluoroethanol offers convenient access triplet 4-hydroxy- 4-methoxyphenyl cations. These add π nucleophiles, viz., 2,3-dimethyl-2-butene, cyclohexene, benzene, giving the arylated products medium good yields. Wagner−Meerwein hydride alkyl migration are evidence for cationic mechanism addition alkenes. Arylation (with no rearrangement) was obtained some extent also nonprotic polar such as MeCN ethyl acetate, reasonably via an exciplex with efficiency proportional nucleophilicity trap (2,3-dimethyl-2-butene > cyclohexene ≫ benzene).