ALPHA-OXOKETENES - PREPARATION AND CHEMISTRY

This review describes the methods of generation of alpha-oxoketenes an d their use in synthesis. While the ketenes are often generated in sit u without direct proof for their existence, methods used for their dir ect observation are also emphasized. The most important classes of pre cursor molecules are 2-diazo-1,3-diketones, 1,3-dioxin-4-ones, 2,3-dih ydrofuran-2,3-diones, and beta-ketoacid derivatives. Synthetically use ful reactions are nucleophilic additions to give carboxylic acid deriv atives which can be subjected to further functional group manipulation , [2 + 2] cycloadditions to give four-membered rings, and [2 + 4] cycl oaddition chemistry with a wide variety of double-and triple-bonded di enophiles, resulting in numerous six-membered heterocyclic ring system s.