The reactions of 2-pyridones with benzyne were investigated in order to gain some insight into the structure–reactivity–chemoselectivity relationship involved in the tautomeric systems. All reactions examined have resulted in the formation of Diels-Alder and Michael-type adducts. It has been shown that the Diels-Alder reactivities were well correlated with the HOMO energy levels of the 2-pyridone form and the yields of the Michael-type adduct were closely associated with the tautomeric equilibria. In summary, the chemoselectivities of 2-pyridones in the reaction with benzyne were largely affected by the tautomeric properties.
The reactions of 1-unsubstituted 2-pyridones with benzyne afforded the Diels-Alder adduct, 5, 6-benzo-2-azabarrelen-3 (2H)-ones, together with a large amount of the Michael-type adduct, 2-phenoxypyridines.