Pd–Cu catalyzed heterocyclization during Sonogashira coupling: synthesis of 2-benzylimidazo[1,2-a]pyridine

Synthesis of 2‐Carbonylimidazo[1,2‐a]pyridines via Iodine–mediated Intramolecular Cyclization of 2‐Amino‐N‐propargylpyridinium Bromides

“…Peak for methyl carbon was observed at 34.1 ppm in the 13 C NMR spectrum and HMRS analysis showed peak at m/z 133.0763 corresponding to molecular formula C 8 H 9 N 2 confirming structure of 3 a . The spectral data of 3 a were in agreement with the reported data …”

Structure–Activity Relationship of Imidazopyridinium Analogues as Antagonists of Neuropeptide S Receptor

“…While the desmethyl compound 10a was commercially available, 2-methylimidazo[1,2-a]pyridine 10b could be accessed via a known palladium catalyzed internal cyclization of the amino group on the pendant alkyne in the 2-amino-1-(propargyl)pyridinium salt 9 . 25 The Tolmachev protocol allowed for the electrophilic aromatic substitution at the 3-position for the introduction of the diphenyl phosphino group. 26 While 10a could be reacted with chlorodiphenylphosphine the 2-methyl counterpart 10b required use of the more reactive iododiphenylphosphine which was generated from chlorodiphenyl phosphine and trimethylsilyliodide.…”

Microwave-Assisted, One-Pot Three Component Synthesis of 2-PhenylH-imidazo[1,2-α]pyridine

“…16 Other methodologies included treating 2-aminopyridines with α-tosyloxyketones, 17 a polymer supported [hydroxy(sulfonyloxy)iodo]benzene with ketones or alcohols, 18 α-diazoketones, 19 and propargyl bromide. 20 Although these methods are suitable for certain synthetic conditions sometimes, however, some of these procedures are associated with one or more disadvantages such as high cost, use of stoichiometric and even excess amounts of reagents or catalysts, long reaction time, hazardous organic solvents, low yield, special apparatus and drastic reaction conditions, which leaves scope for further development of new environmentally clean syntheses. Thus, there is an increasing need for improved and newer methods of synthesis of imidazo [1,2-α] In this Letter, we report a novel and efficient method for the synthesis of 2-phenylHimidazo[1,2-α] pyridine 4 via the coupling of pyridine 1, phenacylbromide 2 and guanidine (urea or thiourea) 3 under microwave irradiation 21 (Scheme 2).…”