General and Efficient α-Oxygenation of Carbonyl Compounds by TEMPO Induced by Single-Electron-Transfer Oxidation of Their Enolates
作者:Emanuela Dinca、Philip Hartmann、Jakub Smrček、Ina Dix、Peter G. Jones、Ullrich Jahn
DOI:10.1002/ejoc.201200736
日期:2012.8
for the synthesis of protected α-oxygenated carbonyl compounds is reported. It is based on the single-electron-transfer oxidation of easily generated enolates to the corresponding α-carbonyl radicals. Coupling with the stable free radical TEMPO provides α-(piperidinyloxy) ketones, esters, amides, acids or nitriles in moderate-to-excellent yields. Enolate aggregates influence the outcome of the oxygenation
报道了一种普遍适用的合成受保护的 α-氧化羰基化合物的方法。它基于将容易生成的烯醇化物单电子转移氧化为相应的 α-羰基自由基。与稳定的自由基 TEMPO 结合以中等至优异的产率提供 α-(哌啶基氧基) 酮、酯、酰胺、酸或腈。烯醇化物聚集体显着影响氧化反应的结果。对竞争反应进行了分析,并提出了将其最小化的条件。产物的化学选择性还原导致 N-O 键裂解为 α-羟基羰基化合物或羰基官能团还原为单保护的 1,2-二醇或 O-保护的氨基醇。