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Preparation of New Nitrogen-bridged Heterocycles. 11. A New Synthetic Method of Pyrazolo[1,5- a ]pyridines from the Alkaline Treatment of 1-[(Acylmethylthio)methyleneamino]pyridinium Salts

1985; Oxford University Press; Volume: 58; Issue: 5 Linguagem: Inglês

10.1246/bcsj.58.1432

1348-0634

Akikazu Kakehi, Suketaka Ito, Masayoshi Ito, Toshiaki Yotsuya, Kenji Nagata,

Synthesis and Biological Evaluation

Abstract Alkaline treatment of 1-[(acylmethylthio)methyleneamino]pyridinium halides gave unexpectedly 3-acyl- or 3-(acylthio)pyrazolo[1,5-a]pyridine derivatives in 35–87% yields. Some 4,4a-dihydropyrido[1,2-d][1,3,4]thiadiazine intermediates involved in these reactions could be detected by their nmr follows and three related 4a,8-dimethyl derivatives were isolated. Substituent effect and possible mechanisms are also discussed.