Abstract
A highly efficient and versatile method for the synthesis of 2-aryl-1H-imidazo[4,5-c]pyridines 3 was achieved in one step via reductive cyclization of 4-amino-3-nitro-pyridines 4 with aromatic aldehydes in the presence of Na2S2O4. Treatment of 3 with benzyl chloride in nonaqueous media under phase-transfer conditions to afford N-benzylated derivatives 10. Compounds 3 and 10 could also be prepared by other routes: dehydrogenative cyclization of monoanil 4-amino-3-arylideneaminopyridine 11 with different oxidizing reagents resulted in the formation of 3, and reduction of 11 with NaBH4, followed by cyclization with aromatic acids using POCl3, gave the N-benzyl-2-aryl-imidazo[4,5-c]pyridines 10. Compound 11 could be synthesized from 3,4-diamino pyridine 1. The structures of all the compounds obtained in the present work are supported by spectral and analytical data.
ACKNOWLEDGMENTS
We thank Azakem Laboratories Pvt. Ltd. management for encouragement and the staff of the analytical laboratories of our research center for spectral analyses.