A catalyst-controlled selective synthesis of pyridines and pyrroles

Abstract

We have developed a dual reaction manifold that enables the selective synthesis of both pyridines and pyrroles from the common substrates α-diazo oxime ethers. The strong propensity of 1,3-dienyl nitrenes for 4π-electrocyclization to give pyrroles could be diverted to 6π-electrocyclization via a 1,6-hydride shift or prototropic isomerization, leading to the exclusive formation of pyridines by employing metal nitrene complexes derived from α-diazo oxime ethers under Rh(II) catalysis. Furthermore, an orthogonal catalytic system has been identified that promotes the selective formation of 1H-pyrroles from the same substrates by redirecting the reactivity of vinyl 2H-azirine intermediates.