Studies on Pyrazolo[3, 4-d]pyrimidne Derivatives. XVII. : Reactions of 5-Benzoyl-4, 5-dihydro-6-methyl-1-phenyl-1H-pyrazolo[3, 4-d]pyrimidine-4-carbonitrile

Acid hydrolysis of the 6-methylpyrazolopyrimidine Reissert compound (6) gave the ring-opened product (12) and the oxazole (13). Alkaline hydrolysis of 6 afforded the 6-methylpyrazolopyrimidine (7) and benzoic acid (15). The anion (1) of 6 mainly underwent both aromatization and rearrangement, resulting in the formation of the 6-methylpyrazolopyrimidinecarbonitrile (20) and the 4-benzoyl-6-methylpyrazolopyrimidine (21) together with by-products such as 7, the dimer (22), the benzoate (23a), and O-benzoylbenzoin (24a). The anion I added to the carbonyl carbon of aromatic aldehydes (8a-c), giving the benzoates (23a-c) together with 7, the O-benzoylaroins (24a-c), and the O-benzoylcyanohydrins (27a, c).