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

Abstract

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.

Competition between Two Modes of 6π‐Photocyclization: A Case Study for 3‐(1,2‐Diarylvinyl)‐2‐arylimidazo[1,2‐a]pyridines

“…In toluene solutions this process is very efficient and gives the products in up to 92 % yields. The explored reaction adequately complements the previously reported approaches towards fluorescent naphtho[1′,2′:4,5]imidazo[1,2‐ a ]pyridine derivatives based on Rh‐, [32,44–46] Cu‐, [42] Pd‐ [31,33] catalyzed annulations of 2‐phenylimidazo[1,2‐ a ]pyridines.…”

“…The main indication of this is a downfieldshifted doublet of H-1 at 9.41 ppm proving the formation of a planar naphtho[1',2':4,5]imidazo[1,2-a]pyridine skeleton. [30][31][32] An electronic spectroscopy study also revealed the irreversible phototransformation of 1 a (Figure 2). Initially, the spectrum of 1 a featured the maximum at ca.…”

“…Based on the NMR data, we could assume that compound 1 a was converted almost quantitatively to product 3 a rather than 2 a . The main indication of this is a downfield‐shifted doublet of H‐1 at 9.41 ppm proving the formation of a planar naphtho[1′,2′:4,5]imidazo[1,2‐ a ]pyridine skeleton [30–32] …”

Sustainable photocatalytic C–H annulation of heteroarenes with sulfoxonium ylides: synthesis and photophysical properties of fused imidazo[1,2-a]pyridine-based molecules

“…6 Among these, a few examples of direct sp 3 C–H functionalization with nucleophiles, like haloalkanes and hydrogen-evolution cross-couplings, including alkoxylation, have been realized by the regioselective C3 C–H activation of imidazo[1,2- a ]pyridines. 7…”