Cu(ii)-catalyzed annulation of α,β-unsaturated ketoxime acetates with 3-formylchromones for the synthesis of functionalized 2,4-diarylpyridines

Abstract

A novel synthesis method has been developed for the construction of functionalized 2,4-diarylpyridines. The reaction involves several key processes, including a reduction reaction, Michael reaction, decarboxylation, intramolecular cyclization, oxidation, ring-opening and aromatization reaction. All of these processes are facilitated by heating a mixture of the starting materials in an environmentally benign solvent, propylene carbonate (PC), with the oxidant (air) and the catalyst Cu(OAc)₂. This cascade reaction not only forms two new bonds but also cleaves three existing bonds in a single pot. The protocol presented in this study is a valuable tool for synthesizing functionalized unsymmetrical 2,4-diarylpyridines.