Synthetic Strategy for Pyrazolo15-apyridineand Pyrido12-bindazoleDerivatives through AcOH and O2-Promoted Cross-dehydrogenativeCoupling Reactions between 13-Dicarbonyl Compounds and N-Amino-2-iminopyridines

摘要

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.