Easy photochemical preparation of 2-dimethylaminophenylfurans, -pyrroles and -thiophenes

2-(4-N,N-dimethylaminophenyl) heterocycles are smoothly obtained from the p hotolysis of 4-chloro-N,N-dimethylaniline in acetonitrile in the presence o f furan, pyrrole, thiophene and some of their methyl derivatives bearing a free or-position. With 2,5-dimethyl heterocycles the arylation occurs with equal efficiency in the beta position. In the case of furan, when the irrad iation is carried out in methanol, cis/trans 2-aryl-5-methoxy-2,5-dihydro a dducts are obtained. The reaction is rationalized as involving heterolytic cleavage of the C-Cl bond in the triplet state of the aniline. The intermed iacy of the thus formed triplet aryl cation explains the observed high regi o- and chemoselectivity of the process. (C) 2000 Elsevier Science Ltd. All rights reserved.