Acylketenes as Reactive Intermediates in the Synthesis of Heterocyclic Compounds: An Overview

Abstract: Acyl ketenes (α-oxoketenes) are extremely versatile synthetic reagents that have been employed in many synthesis. Therefore, there are considerable interests in the chemistry of ketenes due to fact that these compounds are the building blocks of a wide variety of heterocyclic compounds. In organic chemistry, a ketene is an organic compound with carbon-carbon-oxygen cumulative double bonds, which they are known as a branch of cumulenes with replacement of one carbon with oxygen. Acyl ketenes are usually highly reactive molecules, which often prepare from ۲-diazo-۱, ۳-diketones, ۱,۳-dioxin-۴-ones, β-ketoacid and malonic acid derivatives, which cannot be isolated or observed under ordinary reaction conditions. Their synthetically useful reactions are nucleophilic additions, [۲+۲] and [۲+۴] cycloaddition reactions to give four, five or six-membered ring systems. So, the ketene carboxylic acid derivatives such as (chlorocarbonyl)aryl ketenes are extraordinary stable and known as ۱,۳-bielectrophiles, which react with a wide variety of nucleophiles under mild experimental conditions, and have been used mainly for the synthesis of five- and six- membered heterocycles functionalized with oxo and hydroxyl groups in ۱,۳-positions.

کلیدواژه ها:

Acyl ketenes ، α-Oxoketenes ، (Chlorocarbonyl)aryl ketenes ، Cycloaddition reactions ، Heterocyclic compounds