Molecular Rearrangement of 2‐Substituted Indazolones: Unorthodox Access to 2‐Carboxylate‐2,3‐dihydroquinazolin‐4‐(1H)‐one Scaffold.

We disclose a practical and efficient strategy for the expedient synthesis of 2,3‐dihydroquinazolin‐4‐(1H)‐one derivatives by one carbon insertion into cyclic N−N bond. Spontaneous manipulations with operationally simple procedures furnishing pharmaceutically useful compounds are key features of the developed protocol. Mechanistic studies reveal that the predicted intramolecular rearrangement occurs via consecutive ring‐opening and cyclization sequences. A gram‐scale reaction and synthetic transformation of products to quinazolinone derivatives have also been demonstrated during the course of the study. [ABSTRACT FROM AUTHOR]