Abstract
Triazoles and triazolines are important classes of heterocyclic compounds known to exhibit biological activity. Significant focus has been given to the development of synthetic approaches for the preparation of triazoles, and they are today easily obtainable through a large variety of protocols. The number of synthetic procedures for the formation of triazolines, on the other hand, is limited and further research in this field is required. The protocol presented here gives access to a broad scope of 1,4,5-substituted 1,2,3-triazolines through a one-pot transformation of carboxamides. The two-step procedure involves a Mo(CO)6-catalyzed reduction of tertiary amides to afford the corresponding enamines, followed by in situ cycloaddition of organic azides to form triazolines. The amide reduction is chemoselective and allows for a wide variety of functional groups such as esters, ketones, aldehydes, and imines to be tolerated. Furthermore, a modification of this one-pot procedure gives access to the corresponding triazoles. The chemically stable amide functionality is demonstrated to be an efficient synthetic handle for the formation of highly substituted triazolines or triazoles.