Abstract
The 1H-pyrazole-3-carboxylic acid 2 was converted in good yield (69%) into the corresponding 1H-pyrazole-3-carboxamide 5 via reaction of the acid chloride 3 with 2,3-diaminopyridine (4). A different product, the 3H-imidazo[4,5-b] pyridine derivative 6, was formed from the reaction of 3 with 4 and base in benzene for 5 hours. The structures of the synthesized compounds were determined spectroscopically. The mechanism of the reaction between 3 and 4 was examined theoretically.
Highlights
The cyclocondensation reaction of 1,3-dicarbonyl compounds with oxalyl chloride represents a convenient synthesis of furan-2,3-dione systems [1,2,3], which constitute an important group of oxygencontaining heterocyclic starting materials
The chemistry of pyrazole derivatives have been the subject of much interest due to their importance for various applications and their widespread potential and proven biological and pharmacological activities such as antiinflammatory, antipyretic, analgesic, antimicrobial, antiviral, antitumor, antifungal, pesticidal, anticonvulsant, antihistaminic, antibiotics, anti-depressant, and CNS regulant activities [24,25,26,27,28,29,30,31,32]. In view of these important properties, we decided both to prove the reproducibility of the reaction of 4-benzoyl1,5-diphenyl-1H-pyrazole-3-carboxylic acid (2) and acid chloride (3) with a diamine binucleophile 4 and to extend our investigations related to the preparation of new heterocycles, which include two pyrazole rings or 3H-imidazo[4,5-b] pyridine rings in their structure
Compound 5 was synthesized in good yield by refluxing 2,3diaminopyridine (4) and a two-fold molar excess of the pyrazole-3-carboxylic acid 2 or the pyrazole-3carboxylic acid chloride 3 in benzene, without opening of the pyrazole ring
Summary
The cyclocondensation reaction of 1,3-dicarbonyl compounds with oxalyl chloride represents a convenient synthesis of furan-2,3-dione systems [1,2,3], which constitute an important group of oxygencontaining heterocyclic starting materials. The chemistry of pyrazole derivatives have been the subject of much interest due to their importance for various applications and their widespread potential and proven biological and pharmacological activities such as antiinflammatory, antipyretic, analgesic, antimicrobial, antiviral, antitumor, antifungal, pesticidal, anticonvulsant, antihistaminic, antibiotics, anti-depressant, and CNS regulant activities [24,25,26,27,28,29,30,31,32] In view of these important properties, we decided both to prove the reproducibility of the reaction of 4-benzoyl1,5-diphenyl-1H-pyrazole-3-carboxylic acid (2) and acid chloride (3) with a diamine binucleophile 4 and to extend our investigations related to the preparation of new heterocycles, which include two pyrazole rings or 3H-imidazo[4,5-b] pyridine rings in their structure. We are reporting the reaction mechanism, synthesis and characterization of the 1H-pyrazole-3-carboxamide 5 and 3Himidazo[4,5-b]pyridine derivative 6 which were formed by the reaction of the pyrazole-3-carboxylic acid 2 or the pyrazole-3-carboxylic acid chloride 3 with 2,3-diaminopyridine (4) (see Scheme 1)
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