Selective 6π-Electrocyclization of N-Vinyl-α,β-Unsaturated Nitrones to Prepare Polysubstituted Pyridine Derivatives

Herein, we have developed a facile method for the synthesis of various polysubstituted pyridine derivatives through selective 6π-electrocyclization of N-vinyl-α,β-unsaturated nitrones. It was found that gold catalysts promoted carbon-6π-electrocyclization of N-vinyl-α,β-unsaturated nitrones to afford 6-alkenyl pyridine N-oxides in 43%—75% yields, whereas copper catalysts facilitated oxygen-6π-electrocyclization to give 6-epoxy pyridines in 41%—83% yields. The present method features broad substrate scope, good functional group tolerance, high cyclization selectivity, and diversity of polysubstituted pyridine scaffolds.