ピラツォロン誘導体の合成研究 (第8報)

4,5,6,7-Tetrahydro-3H-pyrazolo [4,3-c] pyridineおよび3H-Pyrazolo [3,4-c] pyridine誘導体の合成

抄録

1-Methyl-2, 4-diphenyl-1, 2, 4, 5, 6, 7-hexahydro-3H-pyrazolo [4, 3-c] pyridin-3-one, prepared from 1-phenyl-2-methyl-3-(2-aminoethyl)-3-pyrazolin-5-one and benzaldehyde by the Pictet-Spengler reaction, was catalytically reduced in the presence of formaldehyde and Raney nickel, and a compound N-methylated in 5-position was obtained. The reduction with formic acid and formaldehyde solution resulted in cleavage of the pyridine ring and the decomposition products, 1-phenyl-2-methyl-3-(2-dimethylaminoethyl)-3-pyrazolin-5-one (m. p. 73°) and benzaldehyde, were obtained. Similar Pictet-Spengler reaction with acetaldehyde also afforded the cyclized product.