Easy Photochemical Preparation of 2-Dimethylaminophenylfurans, -Pyrroles and -Thiophenes

2-(4-N,N-dimethylaminophenyl) heterocycles are smoothly obtained from the photolysis of 4-chloro-N,N-dimethylaniline in acetonitrile in the presence of furan, pyrrole, thiophene and some of their methyl derivatives bearing a free α-position. With 2,5-dimethyl heterocycles the arylation occurs with equal efficiency in the β position. In the case of furan, when the irradiation is carried out in methanol, cis/trans 2-aryl-5-methoxy-2,5-dihydro adducts are obtained. The reaction is rationalized as involving heterolytic cleavage of the C–Cl bond in the triplet state of the aniline. The intermediacy of the thus formed triplet aryl cation explains the observed high regio- and chemoselectivity of the process.