bis(trifluoroacetate) (PIFA) and 2,2,6,6‐tetramethyl piperidin‐1‐oxyl (TEMPO) has been described. This unprecedented transformation features mild reaction conditions, simple execution, high chemo‐ and regio‐selectivity, and thereby provides a facile and efficient protocol for the synthesis of polysubstituted 3,7‐dihydro‐ oxazolo[4,5‐c]pyridine‐2,4,6‐(5H)‐triones.
苯基碘(III)双(三氟乙酸)(PIFA)和2,2,6,6-四甲基哌啶-1-氧基(TEMPO)介导的α -[[(β-氨基)丙烯酰基]-烷基酰胺的新型氧化级联环化已经描述过了。这种前所未有的转化具有温和的反应条件,简单的操作,较高的化学和区域选择性,从而为合成多取代的3,7-二氢恶唑[4,5 - c ]吡啶-2提供了简便而有效的方案, 4,6-(5 H)-三酮。
Phenyliodine(III) Diacetate Mediated Oxidative Cyclization of 1-Alkenoyl-1-carbamoyl Cycloalkanes: Access to Spiro-Fused Dihydrofuran-3(2<i>H</i>)-ones
Facile and efficient synthesis of spiro-fused dihydrofuran-3(2H)-ones was developed via phenyliodine(III) diacetate (PIDA) mediated oxidative cyclization of 1-alkenoyl-1-carbamoyl cycloalkanes under very mild conditions.
A convenient and efficient synthesis of spiro-fused pyrazolin-5-one N-oxides starting from readily available 1-carbamoyl-1-oximylcycloalkanes is developed. This general protocol features a novel and facile way for access to the five-membered azaheterocycles by formation of a new N-N single bond. The key cyclization step utilizes the formation of an N-oxonitrenium intermediate, mediated by the hypervalent iodine reagent PIFA, and its subsequent intramolecular trapping by the amide moiety under rather mild experimental conditions.