Brønsted-Acid-Catalyzed In Situ Formation of Acyclic Tertiary Enamides and Its Application to the Preparation of Diverse Nitrogen-Containing Heterocyclic Compounds

A Brønsted acid-catalyzed cascade process, involving
in situ
formation of acyclic tertiary enamides and intramolecular Michael
reaction, is developed for the synthesis of functionalized cyclic
tertiary enamides. Based on the dual reactivities of the enamide moiety,
several reaction sequences were realized by using rationally designed
substrates, leading to biologically relevant nitrogen-containing heterocyclic
compounds with diverse structural skeletons in a concise and diastereocontrolled
manner.