RESUMO
An alternative highly regioselective synthetic method for the preparation of 3,5-disubstituted 4-formyl-N-arylpyrazoles in a one-pot procedure is reported. The methodology developed was based on the regiochemical control of the cyclocondensation reaction of ß-enamino diketones with arylhydrazines. Structural modifications in the ß-enamino diketone system allied to the Lewis acid carbonyl activator BF3 were strategically employed for this control. Also a one-pot method for the preparation of 3,5-disubstituted 4-hydroxymethyl-N-arylpyrazole derivatives from the ß-enamino diketone and arylhydrazine substrates is described.
RESUMO
An efficient one-pot method is described for the highly regioselective synthesis of α-ketoamide N-arylpyrazoles from secondary ß-enamino diketones. For this, the key intermediate, 4-acyl 3,5-dihydroxypyrrolone, was generated in situ and underwent bimolecular nucleophilic substitution at C-5 by arylhydrazine, with subsequent heterocyclization at the carbonyl carbon of the acyl group. This strategy allowed for regiochemical control of α-ketoamide N-arylpyrazoles from ß-enamino diketones and arylhydrazines.