Diverse Functionalization of 2-Pyridinones via Rh(II)-Catalyzed X–H Insertion and Subsequent Transformations Using Heterocyclic Diazo Reagents

Herein, we report a straightforward and diastereoselective synthetic approach to densely substituted 3-RX-dihydropyridin-2(1<i>H</i>)-ones. The method is based on the Rh(II)-catalyzed X-H insertion reaction of previously unreported 3-diazo-3,6-dihydropyridin-2(1<i>H</i>)-ones into a diverse range of X-H substrates (X = N, O, S), followed by base-promoted epimerization. The reaction exhibits broad functional group tolerance in both reaction partners and generally affords the target products in high yields. Furthermore, the resulting 3-allyloxy-substituted dihydropyridin-2-ones were shown to undergo a smooth [3,3]-sigmatropic Claisen rearrangement, providing efficient access to polysubstituted 3-oxopiperidin-2-ones with high diastereoselectivity. The observed stereochemical outcome was further rationalized by DFT calculations.