(CF₃CO)₂O/CF₃SO₃H-mediated Synthesis Of γ-Pyrones From Aromatic Ketones/Heteroarenes And Carboxylic Acids

γ-Pyrones are found in some natural chemical compounds such as chromone,maltol and kojic acid.γ-Pyrone derivatives have good pharmaceutical and pharmacological properties.They could be used as anticancer,antitumor,and antibacterial agents.In organic synthesis,γ-pyrones are also used as the intermediates to prepare pyridinones,3-O-methylfuranone,1-amino-3-hydroxypyridin-4-one and 1,4-dihydropyridine derivatives that present relevant pharmaceutical activity.Through structure modification,γ-pyrone derivatives exhibit attractive optical activity in the field of fluorescent probes,photochromic materials,organic light-emitting diodes(OLEDs),and organic sensitized solar cell.Because of the above wide scope of applications,many researchers devoted much effort to develop the synthetic methods of γ-pyrones.Herein,we demonstrated a(CF3CO)2O/CF3SO3H-mediated ‘one-pot’ synthesis for the preparation of γ-pyrones from commercial aromatic ketones and carboxylic acids under the mild reaction conditions(Scheme 1).1.An efficient and simple synthesis method without metal participation is proposed.The optimal conditions of the reaction were selected through the investigation of reaction dosage and reaction time.Under these conditions,the system showed good selectivity and a series of pyranone compounds were obtained in medium to high yields.The structures of products were identified by HR-MS,NMR,and X-ray single crystal diffraction.2.Based on the previous reports and density functional theory(DFT)calculations,a possible mechanism is proposed in Scheme 2.