Rhenium-Catalyzed Regioselective Synthesis of Multisubstituted Pyridines from β-Enamino Ketones and Alkynes via C-C Bond Cleavage

A new method is described for the regioselective synthesis of multisubstituted pyridine derivatives. Treatment of N-acetyl beta-enamino ketones with alkynes in the presence of the rhenium catalyst, Re-2(CO)(10), gives multisubstituted pyridines regioselectively. In this reaction, the N-acetyl moieties are important for the selective formation of the multisubstituted pyridines. This reaction proceeds via insertion of alkynes into a carbon carbon single bond of beta-enamino ketones, intramolecular nucleophilic cyclization, and elimination of acetic acid.