SELECTIVE ARYLATION OF EXOCYCLIC N-POSITION OF 2-PYRIMIDYLNITRENIUM ION PHOTOLYTICALLY GENERATED FROM TETRAZOLO[1,5-A]PYRIMIDINE IN THE PRESENCE OF TRIFLUOROACETIC-ACID

Photo-reactions of tetrazolo[1,5-a]pyrimidine (1) with benzene (2a) an d substituted benzenes (2b-f) in the presence of trifluoroacetic acid (TFA) gave 2-(2-, 3- and 4-substituted anilino)pyrimidines (3-5) toget her with 2-aminopyridine (6) and biphenyl (7) or diarylmethanes (8b, 8 c and 8e). From the effect of heavy-atom solvent on the reactions, it is reasonable to assume that 3-5 are formed via a singlet species, but 6-8 via a triplet species. The intermediacy of 2-pyrimidylnitrenium i on is consistent with the evidence derived by the above effect, by a H ammett plot with rho = -2.9 and by effects of solvent nucleophilicity and counter-anions. The selective exocyclic N-arylation giving 3-5 is discussed. (C) 1998 John Wiley & Sons, Ltd.