Cu(OTf)2-catalyzed synthesis of imidazo[1,2-a]pyridines from α-diazoketones and 2-aminopyridines

One‐Pot Synthesis of N‐(Imidazo[1,2‐a]pyridin‐3‐yl)‐ and N‐(Imidazo[2,1‐b][1,3]thiazol‐5‐yl)sulfonamides

“…Multi‐component reactions16 of 2‐aminopyridine with aldehydes and isocyanides, nitrile, thiocyanates, imidazoline‐2,4,5‐trione or acetylene, cascade synthesis,17 and palladium catalyzed C–C bond cross‐coupling reactions18 are very promising for the preparation of imidazo[1,2‐ a ]pyridine derivatives. Synthetic approaches based on benzotriazoles,19 pyridinium fluorides,20 diazoketones,21 oxothioamide,22 and vicinal diols23 are also known. A simple method is coupling of 2‐aminopyridine with acetophenones in the presence of acids 24…”

O-Benzenedisulfonimide as a Reusable Brønsted Acid Catalyst for Hetero-Michael Reactions

“…[6] The main disadvantages of many of these methods are the harsh reaction conditions, the relatively long reaction times, the low selectivity and often the use of toxic, corrosive and expensive catalysts in high loading. Moreover their recovery and reuse is often impossible.…”

Microwave‐Assisted, One‐Pot Three Component Synthesis of 2‐Phenyl H‐imidazo[1,2‐α]pyridine

“…15 2-substituted-imidazo[1,2-α] pyridines have been synthesized by cyclocondensation of alkynyl(phenyl)iodonium salts with 2-aminopyridine easily in CHCl 3 under reflux in the presence of K 2 CO 3 . 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.…”