To generalize oxidative radical cyclizations of malonate enolates induced by recyclable single electron transfer (SET) oxidant ferrocenium hexafluorophosphate 1, the reactivity of a series of enolates 3 that differ only in their counterions was studied. Only lithium enolates were oxidized by 1, irrespective of their generation method. The presence of amines in stoichiometric or substoichiometric amounts is necessary for SET oxidationâbicyclization of Na, K, Mg, Zn, Si, or Ti enolates 3. The nucleophilicity of 3, the amine, and the presence of halide ions determine the bicyclization yield of lactone 7.
为了推广可循环型单电子转移(
SET)氧化剂
六氟磷酸铁 1 诱导的
丙二酸烯醇酯的氧化自由基环化,我们研究了一系列烯醇酯 3 的反应性,这些烯醇酯 3 的不同之处仅在于它们的反离子。只有
锂烯醇盐才能被 1 氧化,而与它们的生成方法无关。Na、K、Mg、Zn、Si 或 Ti 烯醇 3 的
SET 氧化双环化过程中,必须有一定量或亚一定量的胺存在。3 的亲核性、胺和卤化物离子的存在决定了内酯 7 的双环化产率。