A Novel Method for the Synthesisof Oxazolocoumarin Derivatives

Abstract

Anodic oxidation of 7-hydroxycoumarin derivatives 1af in anhyd acetonitrile-lithium perchlorate at constant potential between 1.70-1.80 V (vs. Ag/10 -2 M Ag + ) using an undivided cell and platinium gauze electrodes leads to the formation of the corresponding oxazolocoumarin derivatives 2 and/or 3 according to the position of the second OH group in the benzene ring of the coumarin derivatives 1e,f. The formation of these oxidation products is discussed.

One-pot Synthesis of 2-Substituted 4H-Chromeno[3,4-d]oxazol-4-ones from 4-Hydroxy-3-nitrocoumarin and Acids in the Presence of Triphenylphosphine and Phosphorus Pentoxide under Microwave Irradiation

“…27 Heating a mixture of 6-hydroxy-4-methyl-5-nitrocoumarin acetate with iron powder, CH 3 COONa, and (CH 3 CO) 2 O in CH 3 COOH leads to the corresponding oxazolocoumarin. 28 The formation of oxazolocoumarins has likewise been reported by the anodic oxidation 29 of 7-hydroxycoumarin in a solution of MeCN and LiClO 4 and by condensation of 7methoxyimino-4-methylchromen-2,8-dione with methylarenes, or arylacetic esters. 30 Very recently, we have synthesized oxazolocoumarins by one-pot tandem reactions of ohydroxynitrocoumarins with benzyl alcohol in toluene under catalysis with gold nanoparticles supported on TiO 2 , by FeCl 3 or by silver nanoparticles supported on TiO 2 .…”

Synthesis of Fused Oxazolocoumarins from o‐Hydroxynitrocoumarins and Benzyl Alcohol Under Gold Nanoparticles or FeCl3 Catalysis

“…The condensations of 7‐methoxyimino‐4‐methylchromen‐2,8‐dione with methylarenes, arylacetic esters, benzylchloride, or phosphorus ylides gave the corresponding title compounds . Another procedure was by anodic oxidation of 7‐hydroxycoumarin in a solution of MeCN and LiClO 4 .…”