The enantioselective oxidative cyclizations of γ-alkenyl arylsulfonamides and a δ-alkenyl arylsulfonamide for the synthesis of nitrogen heterocycles are presented. The reactions are catalyzed by chiral copper(II) complexes, and MnO2 is used as the inexpensive stoichiometric oxidant. A variety of five-membered heterocycles and a tetrahydroisoquinoline have been synthesized in good to excellent yields with good to excellent levels of enantioselectivity. This is the first reported copper-catalyzed enantioselective carboamination of alkenes.
The de novo synthesis of small organic heterocyclic molecules has benefited from recent protocols for copper-facilitated additions of heteroatoms to alkenes, alkynes and arenes. This tutorial review summarizes a number of these recent contributions. Copper salts can facilitate bond formations due to their ability to serve as Lewis acids, oxidizing agents and transition metal catalysts. The current understanding of the mechanisms of these reactions is presented. This review should be of interest to chemists involved in the synthesis of heterocycles and those investigating transition metal facilitated reactions.
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