tailieunhanh - Synthesis of imidazo[1,2-a]-pyridine derivatives

The synthesis of imidazo[1,2-a]-pyridine derivatives was carried out by subsequential reactions: condensation, substitution and reduction, using the commercially available 2- aminopyridine as starting material. | Journal of Chemistry Vol. 45 6 P. 781 - 784 2007 SyNTHESIS OF IMIDAZO 1 2-a -PyRIDINE DERIVATIVES Received 2 April 2007 TRAN VAN CHIEN DAO Duc THIEN TRAN VAN Loc TRAN VAN SUNG Department of organic synthesis Institute of Chemistry Vietnamese Academy of Science and Technology SUMMARY The synthesis of imidazo 1 2-a -pyridine derivatives was carried out by subsequential reactions condensation substitution and reduction using the commercially available 2-aminopyridine as starting material. Keywords 2-aminopyridine 2-chloroimidazo 1 2-a -pyridine 1 1 -carbonyldiimidazole. I - INTRODUCTION Alkaloids one of the most naturally abundant organic compound classes are well known for their bioactivities. The total or semisynthesis of alkaloids has been focused due to the pharmacological interest. Imidazo 1 2-a -pyridine and its derivatives are interesting compounds because of their gastric antisecretory 1 2 local anesthetic 3 antiviral antibacterial 4 hypnotic and antianxiety 5 antimicrobial antiulcer 6 cytoprotective activity and against respiratory of syncytial virus 7 . The nature and position of the substituents on the imidazole or pyridine moiety also affect much to their activities 4 . In this paper we present the preparation of some new imidazo 1 2-a -pyridine derivatives. The structures of synthesized compounds were determined by IR 1H- 13C-NMR and mass spectra analysis. II - EXPERIMENTAL 1. Preparation of 2-chloroimidazo 1 2-a -pyridine 3 A mixture of monochloroacetic acid 106 mmol and Na2CO3 128 mmol was dissolved in 60 ml H2O. 2-aminopyridine 100 mmol was added slowly into the mixture. The mixture was then refluxed for 5 hours. The white solid was precipitated filtered and dissolved again in 25 aqueous NaOH 50 ml . The solution was refluxed for further 5 min cooled in an ice bath. The salt was then filtered washed with isopropanol and dried at 50oC in vacuo. The salt obtained above was refluxed in POCl3 20 ml for h. The mixture was extracted with CH2Cl2 3x 250 ml