Synthesis of Imidazo[1,2‐a]pyridines: C‐H Functionalization in the Direction of C‐S Bond Formation

Abstract

Imidazo[1,2-a]pyridines play an important role in medicinal chemistry. In spite of very drastic developments on syntheses and functionalization in this area, the use of inexpensive catalysts and mild reaction conditions constitutes an important role in pharmaceutical applications. This account describes our recent efforts on the development of new methods for the synthesis of imidazo[1,2-a]pyridines using readily available starting substrates and catalysts under very mild reaction conditions. In the direction of enhancement of biological activity, we also described the synthesis of functionalized imidazo [1,2-a]pyridine derivatives.

Multicomponent Synthesis of Structurally Diverse Imidazoles Featuring Azirines, Amines and Aldehydes

“…The tetrasubstituted imidazoles 4 obtained by this method are structurally diverse scaffolds that can be readily manipulated to improve the chemical complexity. To further demonstrate the synthetic potential of imidazoles 4 as useful building blocks, we designed an intramolecular palladium‐catalyzed Heck reaction for the synthesis of an analogue of zolpidem, a sedative used for the treatment of sleep disturbances. Accordingly, starting from imidazole 4c , the microwave‐assisted intramolecular coupling was successfully achieved in a short time to give the expected fused tricycle 15 in good isolated yield (Scheme ).…”

Thiosulfonates as Emerging Reactants: Synthesis and Applications

“…[175] TheM aes group used S-methyl methanethiosulfonate (9)a sa n electrophile to quench magnesiated pyridazin-3(2H)-Scheme 71. Synthesis of dithioketal (179,181)derivatives. Scheme 72.…”

“…Adimurthy et al developed ac atalyst-free route for the C À Hs ulfenylation of av ariety of imidazo[1,2a]pyridines (219)a nd imidazothiazoles (Scheme 81). [181] This protocolh as ab road functional group tolerance andc ould easily be extended to the C-3 sulfenylationo fi ndoles ( 220). Interestingly,t he reactiond oes not proceed via ar adical pathway, but rather via an electrophilic sulfenylation of the C-3 po-sition of the nitrogen-heteroarene.T he authors argue that water as solvent facilitates an initial dissociation of thiosulfonates (7)into asulfinate anion and asulfenyl cation, and the latter is trapped by the electronrich heteroarenes.…”

Photoinduced, Direct C(sp2)−H Bond Azo Coupling of Imidazoheteroarenes and Imidazoanilines with Aryl Diazonium Salts Catalyzed by Eosin Y

“…Their structure is present in many pharmaceuticals and also has applications in material sciences . Therefore, it is not surprising that the synthesis and functionalization of imidazoheteroarenes have received considerable attention in different areas of scientific research . Analogously, arylazo compounds are widely used in several areas, including the chemical industry, pharmaceuticals, chemosensors, electronics, and liquid crystals ( 1 a – d , Figure ) .…”