Selective arylation of exocyclic N-position of 2-pyrimidylnitrenium ion photolytically generated from tetrazolo-[1,5-a]pyrimidine in the presence of trifluoroacetic acid
✍ Scribed by Hiroshi Takeuchi; Keiichi Watanabe
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 141 KB
- Volume
- 11
- Category
- Article
- ISSN
- 0894-3230
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✦ Synopsis
Photo-reactions of tetrazolo [1,5-a]pyrimidine (1) with benzene (2a) and substituted benzenes (2b-f) in the presence of trifluoroacetic acid (TFA) gave 2-(2-, 3-and 4-substituted anilino)pyrimidines (3-5) together with 2aminopyridine (6) and biphenyl (7) or diarylmethanes (8b, 8c 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 ion is consistent with the evidence derived by the above effect, by a Hammett plot with r = À2.9 and by effects of solvent nucleophilicity and counter-anions. The selective exocyclic N-arylation giving 3-5 is discussed.