Abstract
The styryl ketonic Mannich base 2 has been used as a precursor in the synthesis of 2‐pyrazolines having a basic side chain at C‐3 and a phenolic Mannich base at C‐5. Treatment of the bis(styryl ketonic bases) 6a and 8a with phenylhydrazine affords the bis(3‐functionalized 2‐pyrazolines) 7 and 9. The transamination between the styryl keto base 10 and 4‐aminoantipyrine leads to 12, which reacts with piperazine to give 13. N‐Nitrosation of the sec‐Mannich bases 15a–d followed by reductive cyclization affords 2‐pyrazolines 17a–d. The keto base 14b has been used for the synthesis of 2‐pyrazolines having a phenolic Mannich base at C‐3 and its reaction with 3,5‐dimethyl‐1H‐pyrazole affords 23. The alkylation of 3‐methyl‐1‐phenyl‐2‐pyrazolin‐5‐one with the bis(Mannich base) 25 was investigated.
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