A method for the construction of pyrroles bearing a 2-keto or formyl group through the intramolecular oxidative aza-annulation of enynyl azides is reported for the first time. It involves a sequential carbon-nitrogen/carbon-oxygen bond formations, and the combination of AuCl with AgSbF was identified as a suitable reagent system to promote the present reaction. The required enynyl azides are readily prepared from Morita-Baylis-Hillman (MBH) acetates of acetylenic aldehydes.

Synthesis of substituted pyridines through a novel aza-annulation of 2-en-4-ynyl azides, derived from MBH-acetates of acetylenic aldehydes, is described. A variety of enynyl azides having aryl, heteroaryl, and alkyl groups on the alkyne functionality successfully participated in the Ag-mediated annulation reaction to provide the corresponding 3,6-disubstituted pyridines. I2-mediated cyclization was found to be controlled by the substituent on the alkyne functionality, which offered the 5-iodo-3,6-disubstituted pyridines from enynyl azides having an electron-rich substituent on the alkyne functionality.

Aza-Annulation of Enynyl Azides: A New Approach to Substituted Pyridines. -A novel aza-annulation of 2-en-4-ynyl azides, derived from MBH-acetates of acetylenic aldehydes, to synthesized substituted pyridines is developed. A broad range of enynyl azides bearing aryl, heteroaryl, and alkyl groups on the alkyne moiety are successfully employed in this reaction. The outcome of the I 2-mediated annulation strongly depends on the substituent giving either iodopyridine or acyl-pyrrole. This method provides a new access to structurally diverse nicotinate. -(RAJI REDDY*, C.; PANDA, S. A.; REDDY, M. D.; Org. Lett. 17 (2015) 4, 896-899,