Recent advances in metal-free functionalization of 1,4-benzoxazin-2-one scaffolds.

Transition metal free methodologies have emerged as sustainable alternatives for the functionalization of biologically important heterocylic scaffolds. Among the heterocycles 1,4-benzoxazin-2-one has attracted considerable interest owing to its diverse pharmaceutical and agrochemical applications. In this review, we summarize the recent advances in the transition metal-free functionalization of 1,4-benzoxazin-2-one, highlighting the organocatalytic transformations, main group Lewis acid/base promoted reactions, visible-light mediated and ultrasound assisted multicomponent reactions. Special emphasis is given to methodologies that enable the efficient synthesis of biologically active 1,4-benzoxazin-2-one derivatives. The reaction scope, mechanistic aspect, regio and stereoselectivity, and synthetic applications of these methodologies are critically discussed to provide a comprehensive overview of this rapidly developing area.