Diketene a Privileged Synthon in the Synthesis of Heterocycles. Part 2: Six-Membered Ring Heterocycles

Diketene is an ideal molecule for use in many organic transformations, since it possesses electrophilic and nucleophilic sites which react with numerous functional groups. Diketene is mostly used as the common starting material for structurally diverse mono-, spiro-, and fused six-membered heterocycles such as lactones, pyrans, pyridines, quinolines, isoquinolines, oxazine, quinoxalines, benzothiazinone, 1,4-thiazidines, and oxazinonethione.