A New and Efficient Approach to Cyclic β-Enamino Esters and β-Enamino Ketones by Iodine-Promoted Cyclization

摘要

The development of new methods for preparing nitrogen five-membered rings, such as pyrrolidine and pyrrole derivatives, continues to be an active research area, since they are useful intermediates for the synthesis of many natural products. Cyclic β-enamino esters and ketones are the subject of continuous synthetic studies, as attested by a number of recent papers dealing with reactivity and synthetic applications of these compounds. In particular, the exocyclic β-enamino ester of general formula 1 has found widespread application in the synthesis of several alkaloids, such as pyrroloindoloquinones, anatoxin-a, camptothecin analogues, and other pyrrolizidine and indolizidine systems.