Synthesis of 2-, 3- and 4-(Phenylseleno)benzonitrile by Electrochemically Induced Aromatic Nucleophilic Substitution in Acetonitrile

Article abstract of DOI:10.1021/jo00384a008

2-, 3- and 4-bromobenzonitrile have been electrolyzed in acetonitrile with sonication in the presence of an equivalent amount of benzeneselenate initially prepared by electrochemical reduction of diphenyl diselenide.Thus 2-, 3-, and 4-(phenylseleno)benzonitrile have been isolated in 36percent, 42percent, and 59percent yields, respectively.The electrochemically generated aryl radical NCC6H4* which is involved in the S_RN1 mechanism is deactivated partially by its further reduction to the corresponding anion and so the yields remain moderate.These yields can be improved by electrolysis of chlorobenzonitrile.A yield of 70percent has been thus achieved in the case of 4-(phenylseleno)benzonitrile.The two-electron cathodic reduction of the seleno derivatives is accompanied by the formation of cyanobenzeneselenate.Electrochemical reduction of 4-(phenylseleno)benzonitrile followed by chemical oxidation by air has given a mixture of 4,4'-dicyanodiphenyl diselenide and diphenyl diselenide, which have been isolated in 76percent and 24percent relative yields, respectively.