Synthesis of Pyridine Derivatives from Acetophenone and Ammonium Acetate by Releasing CH₄

Abstract

An efficient copper-catalyzed cyclization of acetophenone and ammonium acetate with release of methane has been developed for the synthesis of polysubstituted pyridines. A series of 2,4,6-triphenyl-pyridines has been produced in good yields. This synthetic method is sustainable, simple, and environment-friendly.

One-Pot Synthesis of 1,5-Diketones under a Transition-Metal-Free Condition: Application in the Synthesis of 2,4,6-Triaryl Pyridine Derivatives

“…Our finding reveals that 1,5-diones with weak electron-donating groups, such as methyl and chloro groups, on the aromatic ring could provide relatively higher yields of the corresponding 2,4,6-triaryl-substituted pyridines ( 5a–d ) than those substrates with strong electron-donating groups, such as the methoxy group ( 5e ). These results are in accordance with those reported by Chen et al., who synthesized numerous polysubstituted pyridines using a one-pot protocol with Cu­(OTf) 2 as the catalyst. − …”

“…Functionalized pyridines are among the most common heterocyclic compounds that have been used in therapeutic drugs, , chemosensors, photosensitizers, as ligands for catalysis, and as starting materials in the synthesis of agricultural chemicals such as insecticides, herbicides, and surfactants . Thus, several synthetic methods have been established to produce 2,4,6-triaryl pyridine derivatives. − The most common approach for the synthesis of substituted pyridine is ammonium acetate (NH 4 OAc)-mediated cyclization of 1,5-diketones. ,− Accordingly, the treatment of 1,5-diketones 3 and 4 with NH 4 OAc as a nitrogen source successfully produced good yields of the reported pyridine-based molecules 5a–e ,,, within a moderate reaction time under a catalyst-free system (Table ). Our finding reveals that 1,5-diones with weak electron-donating groups, such as methyl and chloro groups, on the aromatic ring could provide relatively higher yields of the corresponding 2,4,6-triaryl-substituted pyridines ( 5a–d ) than those substrates with strong electron-donating groups, such as the methoxy group ( 5e ).…”