Anodic Reaction of 2-Furoic Acids. II. Electrolysis of Methyl 5-Acetyl-2-furoate and Its Homologous in Protic Solvents

Abstract Anodic oxidation of methyl 5-acetyl-2-furoate 4 in methanol leads to ring-opened diesters 8 and 9, and lactone 10 in addition to methyl 5-acetyl-2,5-dimethoxy-2,5-dihydro-2-furoates 7. Formation of 8, 9, and 10 can be rationalized as arising from 7. On the other hand, oxidation of methyl 5-methoxy- and 5-bromo-2-furoates, 5 and 6, also give 9 and 10. The reactions involve initial production of cationic intermediates 13 and 15, which are readily solvolized to give 8, 9, and 10. A mechanism of the formation of the intermediates 13 from 5, 6, and 7 is discussed.