Nickel-catalyzed Cycloaddition of α,β-Unsaturated Oximes with Alkynes: Synthesis of Highly Substituted Pyridine Derivatives

A nickel-catalyzed cycloaddition of alpha,beta-unsaturated oximes with alkynes to afford 2,3,4,6-tetrasubstituted pyridine derivatives has been developed. The reaction involves oxidative addition of the N-O bond of alpha,beta-unsaturated oximes to Ni(0) and subsequent alkyne insertion to an N-Ni bond, followed by intramolecular cyclization. It was also found that beta,gamma-unsaturated oximes participate in the nickel-catalyzed reaction with alkynes to furnish pyridine derivatives.