Synthetic Strategy for Pyrazolo[1,5- a]pyridine and Pyrido[1,2- b]indazole Derivatives through AcOH and O2-Promoted Cross-dehydrogenative Coupling Reactions between 1,3-Dicarbonyl Compounds and N-Amino-2-iminopyridines

Haider Behbehani; Hamada Mohamed Ibrahim

doi:10.1021/acsomega.9b02430

Synthetic Strategy for Pyrazolo[1,5- a]pyridine and Pyrido[1,2- b]indazole Derivatives through AcOH and O₂-Promoted Cross-dehydrogenative Coupling Reactions between 1,3-Dicarbonyl Compounds and N-Amino-2-iminopyridines

ACS Omega. 2019 Sep 4;4(12):15289-15303. doi: 10.1021/acsomega.9b02430. eCollection 2019 Sep 17.

Authors

Haider Behbehani¹, Hamada Mohamed Ibrahim^{1

2}

Affiliations

¹ Chemistry Department, Faculty of Science, Kuwait University, P.O. Box 5969, Safat 13060, Kuwait.
² Chemistry Department, Faculty of Science, Fayoum University, P.O. Box 63514, Fayoum, Egypt.

Abstract

An efficient method has been developed for the synthesis of uniquely substituted pyrazolo[1,5-a]pyridine and pyrido[1,2-b]indazole derivatives, which involves acetic acid and molecular oxygen promoted cross-dehydrogenative coupling reactions of respective β-ketoesters and β-diketones (like ethyl acetoacetate, ethyl benzoylacetate, methyl propionylacetate, acetylacetone, dimedone, 1,3-cyclohexanedione, and 1,3-cyclopentanedione) with N-amino-2-iminopyridines. The proposed tentative mechanism involves formal acetic acid-promoted oxidative C(sp³)-C(sp²) dehydrogenative coupling followed by dehydrative cyclization under a catalyst-free condition within high atom economy processes.