Synthesis of Spiro-lactams and Polysubstituted Pyrroles via Ceric Ammonium Nitrate-Mediated Oxidative Cyclization of N‑Furan-2-ylmethyl‑β-Enaminones

Spiro-lactams and polysubstituted pyrroles were synthesized by reactions of furfurylamines with ynones followed by oxidation. Specifically, the protocol involved in situ generation of N-furan-2-ylmethyl-β-enaminones and their subsequent oxidation by ceric ammonium nitrate (6 equiv for spiro-lactam formation, 3 equiv for pyrrole formation). This useful dearomatizing oxidation, which likely proceeds via a free-radical pathway, can be expected to extend the synthetic applications of furan and pyrrole derivatives.