One‐Pot Synthesis of Naphtho[1′,2′:4,5]imidazo[1,2‐ a ]pyridin‐5‐yl(aryl)methanones through Sequential Sonogashira Coupling/Alkyne–Carbonyl Metathesis

An efficient one‐pot route for the construction of naphtho[1′,2′:4,5]imidazo[1,2‐ a ]pyridin‐5‐yl(aryl)methanones and 5‐phenylnaphtho[1′,2′:4,5]imidazo[1,2‐ a ]pyridines by sequential Sonogashira coupling reaction followed by trifluoroacetic acid promoted alkyne‐carbonyl metathesis (ACM) has been developed. 2‐(2‐Bromophenyl)imidazo[1,2‐ a ]pyridine‐3‐carbaldehyde preferentially underwent ACM with phenyl acetylenes, whereas intramolecular hydroarylation reaction was the common pathway in the absence of a carbonyl moiety at the C‐3 position under similar conditions. This protocol is compatible with a wide variety of functional groups and delivered corresponding naphtho[1′,2′:4,5]imidazo[1,2‐ a ]pyridines in good to excellent yields.