Radical ions in photochemistry. 12. The photoaddition of olefins to cyano aromatic compounds in polar solvents
The photochemical reactions of 1,L_dicyanobenzene (1) and dicyanonaphthalene (2) with 2,3-dimethyl-2-butene (L) in acetonitrile solution have been studied. Irradiation of 1 and gives the photosubstitution products , 2 ,3-dimethyl-l-(4-cyanopienyl)2-butene (J)+) and 2 ,3dimethyl-3-(4-cyanophenyl)-l-butene (15). Irradiation of 2 and 4, on the other hand, gives l,4—dicyano-5,6 ,6-trimethyl-2 ,3-benzotricyclo[3.3.l.O'7]nonane (), l,4-dicyano-5,9,9-trimethyl-2,3-benzotricyclo-[3.3.1.0'7]nonane Q;Z) ' and 1,5-dicyano-2,2,3-trimethyl-6 ,7-benzotricyclo[3.2.2,O3'8]nonane (). The structures of 16, 17 arid 18 have been established by X-ray crystallographic analysis. It is proposed that both reactions initially involve radical ion intermediates. Generalizations, useful for predicting the result of irradiating cyano aromatic compounds in the presence of olefins are formulated.