A Simple Transformation of 1‐(Isoxazol‐3‐yl)ureas to 5‐(2‐oxoalkyl)‐2,4‐dihydro‐3H‐1,2,4‐triazol‐3‐ones through Base‐Promoted Boulton‐Katritzky Rearrangement.

2,4‐Dihydro‐3H‐1,2,4‐triazol‐3‐ones are a class of biologically important heterocycles. A novel and simple synthesis of such structures is developed. The method is through a base‐promoted Boulton‐Katritzky‐type rearrangement of 1‐(isoxazol‐3‐yl)ureas and is highly efficient for the formation of 2,4‐dihydro‐3H‐1,2,4‐triazol‐3‐ones. [ABSTRACT FROM AUTHOR]