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Synthesis 2001(12): 1861-1865
DOI: 10.1055/s-2001-17522
PAPER
© Georg Thieme Verlag Stuttgart · New York

Chemistry of 2-Arylhydrazonopropanals: Novel Synthesis of 1,6-Dihydropyridazines and 5-Heteroaryl Substituted Pyrazolo[1,5-a]Pyrimidines and Pyrazolo[3,4-b]Pyridines

Mervat Mohammed Abdel-Khalika, Samia Michel Agamya, Mohammed Hilmy Elnagdi*b
a Department of Chemistry, Girls College for Arts, Science and Education, Ain Shams University, P.O. Box 11757 Heliopolis, Cairo, A.R. Egypt
b Department of Chemistry, Faculty of Science, Cairo University, Giza, A.R. Egypt
e-Mail: shelmy@access.com.eg;
Further Information

Publication History

Received 10 April 2001
Publication Date:
11 August 2004 (online)

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Abstract

The reaction of 2-arylhydrazonopropanals 1a-d with dimethyl acetylenedicarboxylate in anhydrous dichloromethane in the presence of triphenylphosphine afforded 1,6-dihydropyridazines 2a-d. Compound 1a reacted with dimethyl acetylenedicarboxylate in refluxing acetic acid yielding the corresponding Michael adduct 4. Whereas compound 1d failed to react in acetic acid with diphenylacetylene, its reaction with the same reagent in anhydrous dichloromethane in the presence of triphenylphosphine afforded the Michael adduct 3. Compounds 2b-d reacted with hydrazine hydrate affording the corresponding pyridazino[3,4-d]pyr-idazines 6b-d. 2-Arylhydrazonopropanals 1a,b reacted with 5-methyl-1H-pyrazol-3-amine in ethanol yielding the corresponding condensation products 8a,b, which cyclized to the 7-substituted 2-methyl-6-phenylazopyrazolo[1,5-a]pyrimidines 9a,b and 4-substituted 3-methyl-5-phenylazopyrazolo[3,4-b]pyridines 10a,b on refluxing in acetic acid. 2-Phenylhydrazonopropanal 1a reacted with p-benzoquinone yielding the resorcinol derivative 12.

Key words

heterocycles - Michael addition - cyclization

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