ピラツォロン誘導体の合成研究 (第7報)

Pyrazolo [4,3-c] pyridine誘導体の合成

抄録

Bischler-Napieralsky reaction of 3-(2-homoveratramidoethyl)- and 1-phenyl-2-methyl-3-[2-(2-phenylacetamido) ethyl]-3-pyrazolin-5-one was carried out and its reaction product was examined. When phosphoryl chloride was used as the reagent, the cyclized product, 1-methyl-2-phenyl-4-veratryl-1, 2, 6, 7-tetrahydro-3H-pyrazolo-[4, 3-c]pyridin-3-one (A) was not obtained and a compound in which the bridged side-chain CH₂ had been oxidized to CO, i.e. 1-methyl-2-phenyl-4-veratroyl-1, 2-dihydro-3H-pyrazolo [4, 3-c] pyridin-3-one (B), and its 4-benzoyl compound (C) were obtained. In the case of phosphorus pentachloride, majority of the product was (B) or (C), but (A) was also formed to some extent. By the use of pyridine and phosphorus pentoxide, a cyclization reagent used in the modified Sugasawa method, (A) was obtained in a low yield. A few other cyclized compounds were also prepared.