Silver‐Mediated Cascade Synthesis of Functionalized 1,4‐Dihydro‐2H‐benzo‐1,3‐oxazin‐2‐ones from Carbon Dioxide.

A conceptually novel catalytic domino approach is presented for the synthesis of highly functional 1,4‐dihydro‐2H‐1,3‐benzoxazine‐2‐one derivatives. Key to the chemoselectivity is a proper design of the precursor to override thermodynamically favored parasitic cyclization processes and empower the formation of the desired product through Thorpe–Ingold effects. The synthetic diversity of these CO2‐based heterocycles is further demonstrated, and the isolation of a reaction intermediate supports an unusual ring‐expansion sequence from an α‐alkylidene, five‐membered cyclic carbonate to a six‐membered cyclic carbamate by N‐induced isomerization. [ABSTRACT FROM AUTHOR]