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.
甲醇中甲基5-乙酰基-2-
呋喃酸酯的阳极氧化反应形成了环开二酯8和9,以及内酯10和甲基5-乙酰基-2,5-二甲氧基-2,5-四氢-2-
呋喃酸酯7。8、9和10的形成可以合理化为源于7。另一方面,甲基5-甲氧基和5-
溴-2-
呋喃酸酯5和6的氧化反应也会生成9和10。这些反应涉及初步生成的阳离子中间体13和15,它们很容易发生溶剂化反应生成8、9和10。文中讨论了从5、6和7形成中间体13的机制。