The irradiation of 1, 4-dicyanobenzene (DCB) in the presence of 2, 3-dimethyl-2-butene (DMB) leads to allylation of the aromatic. In the presence of nucleophiles (MeOH, H2O, CF3CH2OH) this reaction is substituted by the nucleophile olefin combination-aromatic substitution (NOCAS) process. The quantum yield increases from 0.006 in the absence to a limiting value of ca 0.02 in the presence of the nucleophiles. The reaction involves ...