4‐Oxo‐2‐cyclopentenyl Acetate—A Synthetic Intermediate

Abstract

Abstract The present day importance of cyclopentenone derivatives in preparative organic chemistry and especially in natural product chemistry is demonstrated by the stereoselective synthesis of substituted and annelated cyclopentanone derivatives. It has been found that 4‐oxo‐2‐cyclopentenyl acetate (“4‐acetoxy‐2‐cyclopenten‐1‐one”) can be used in many reactions as a substitute for cyclopentadienone, which is itself too unstable to be isolated. A large variety of polyfunctionalized cyclopentanone derivatives, as well as carbocyclic and heterocyclic annelation products, can thus be obtained in a simple way. Various stereoselective transformations of the adducts so formed are presented, using the total synthesis of brefeldin A—a typical natural product of this series—as example. Several methods for the synthesis of 4‐oxo‐2‐cyclopentenyl acetate are outlined and, in addition, the more important methods for the enantioselective synthesis of other 4‐substituted 2‐cyclopenten‐1‐ones are discussed.