Palladium-Catalyzed Cascade Carbonylative Synthesis of 1,2,4-Triazol-3-ones from Hydrazonoyl Chlorides and NaN3.

A palladium-catalyzed three-component carbonylative reaction for the synthesis of 3H-1,2,4-triazol-3-ones from hydrazonoyl chlorides and NaN3 has been achieved. The reaction presumably proceeds through a cascade carbonylation, acyl azide formation, Curtius rearrangement, and intramolecular nucleophilic addition sequence. A wide variety of structurally diverse 3H-1,2,4-triazol-3-ones were constructed in moderate to excellent yields. Benzene-1,3,5-triyl triformate (TFBen) was applied as a solid and convenient CO surrogate.