Construction of 2-Pyridones and Pyridines via Ring-Closing Metathesis

Significance

Reported here is a ring-closing metathesis (RCM)-based synthetic route for substituted dihydro 2-pyridones and pyridine derivatives, the latter being derived from the intermediate dihydropyridone via base-induced elimination. The required starting materials are readily obtained from the corresponding amines by allylation of oximes followed by N-alkylation with α,β-unsaturated acid chlorides. The formation of the C3-C4 bond of 2-pyridone was achieved by RCM employing the Hoveyda-Grubbs second-generation catalyst. Best results for the elimination to 2-pyridones was achieved using DBU; triflation of the latter by the useful Comins method gave pyridine triflates which are potential cross-coupling partners.