Pd-catalyzed regiocontrolled Sonogashira and Suzuki cross-coupling reaction of 3,6-dihalogenoimidazo[1,2-a]pyridines: one-pot double-coupling approach

Domino Benzylic‐Amination–Sonogashira–Heterocyclisation Reaction: Direct Access to Dipyrido[1,2‐a:3′,4′‐d]imidazole Salts

“…For example, an ester group in this position reduced the reactivity towards Sonogashira coupling, so that such a cross‐coupling was only achieved by coupling with phenylacetylene 15,16. More recent papers have reported the reaction of 3‐haloimidazo[1,2‐ a ]pyridines substituted by a hydrogen, a phenyl group,17 or a cyano group18 at the 2‐position. However, to the best of our knowledge, such cross‐coupling reactions have never been reported with 2‐chloromethyl or 2‐aminomethyl‐3‐haloimidazo[1,2‐ a ]pyridines.…”

Selective Palladium‐Catalyzed Suzuki–Miyaura Reactions of Polyhalogenated Heteroarenes

“…Bertana‐Raboin et al. have found that the Suzuki–Miyaura reaction of 3‐bromo‐6‐iodo‐2‐phenylimidazo[1,2‐ a ]pyridine with (hetero)arylboronic acids occurs with excellent chemoselectivity at the CI bond using a Pd(OAc) 2 /PPh 3 catalyst system 209. However, a catalyst system consisting of a mixture of Pd 2 (dba) 3 ⋅CHCl 3 and AsPh 3 was used for the C‐3 arylation of 6‐bromo‐3‐iodo‐2‐phenylimidazo[1,2‐ a ]pyridine 209…”

Functionalization of Imidazo[1,2‐a]pyridines by Means of Metal‐Catalyzed Cross‐Coupling Reactions

“…Very recently, some of us developed two efficient methods based on either microwave‐assisted one‐pot bis‐Sonogashira or microwave‐assisted one‐pot bis‐Suzuki reactions of 3,6‐dihaloimidazo[1,2‐ a ]pyridines. For the first study, alkynes were used as coupling partners, leading to the synthesis of various 2,3,6‐trisubstituted imidazo[1,2‐ a ]pyridine derivatives 98. 3‐Bromo‐6‐iodo‐2‐phenylimidazo[1,2‐ a ]pyridine ( 169 ) or 6‐bromo‐3‐iodo‐2‐phenylimidazo[1,2‐ a ]pyridine ( 170 ) were treated successively with the first alkyne (1.1 equiv.)…”

“…was added and the reaction mixture was irradiated again for 2 h at 140 °C (second coupling). These sequences afforded the desired polysubstituted imidazo[1,2‐ a ]pyridine 173 in good overall yield (69–71 %)98 (Scheme ).…”