Although organometallic mediated conjugate addition of alkyl or aryl ligands to 4-pyridones could provide a rapid entry to the highly versatile 2,3-dihydropyridones, the addition of an allyllithium reagent appears to be the only reported example of such a reaction. While copper and rhodium mediated conjugate additions to 2,3-dihydropyridones are well established, the addition of nucleophiles to pyridinium salts is employed as a synthetic alternative to a 4-pyridone conjugate addition strategy. We now report that a variety of organometallic reagents do in fact undergo conjugate addition reactions with N-carbamoyl-4-pyridones. Lithium diphenyl- and dialkylcuprates, as well as the corresponding cyanocuprate reagents, readily add to N-carbamoyl-4-pyridones when the reaction is conducted in THF in the presence of trimethylsilylchloride (TMSCl). In the interest of developing an asymmetric variation of the reaction, a series of procedures catalytic in copper were examined.

The fully unsaturated 2-pyrones possess aromatic character, and display reactivity patterns characteristic of lactones, 1,3-dienes, and heteroaromatic rings. Although organocopper mediated conjugate addition reactions to 2- and 4-pyrones have not been reported, cuprate reagents could be successfully added by conversion of the pyrones to pyrilium salts with added triflic anhydride. These reactions proceeded with addition of the ligand to the 4-position of the pyrone ring. We now report that organocuprate reagents do indeed undergo 1,4-conjugate addition reactions with 2- and 4-pyrones.