α,β-Unsaturated oximes underwent electrophilicepoxidation with in-situ-generated dimethyldioxirane to give the corresponding epoxides in good yields. This reaction is an example of “carbonyl umpolung” by transformation of α,β-unsaturated ketones to their oximes. Nucleophilic ring-opening reactions of the epoxides afforded α-substituted products. Shi asymmetric epoxidation of the oximes proceeded with
α,β不饱和肟经历亲电环氧化与在-原位-生成二甲基二以得到良好的产率相应的环氧化物。该反应是通过将 α,β-不饱和酮转化为其肟的“羰基聚合”的一个例子。环氧化物的亲核开环反应得到α-取代的产物。肟的 Shi 不对称环氧化反应具有中等的对映选择性。 全尺寸图像
Synthesis of chiral isoxazolidin-5-ones and their applications to the synthesis of β-amino-alanines and β-(N-hydroxyamino)-alanines
作者:Jack E. Baldwin、Robert M. Adlington、Lisa C. Mellor
DOI:10.1016/s0040-4020(01)90416-8
日期:1994.4
Herein we report a high-yielding synthesis of isoxazolidin-5-ones and their use to synthesise both β-amino-alanines and β-(N-hydroxyamino)-alanines.
Cycloaddition of nitrones with [small alpha],[small beta]-unsaturated carbonyl compounds (enones) afforded predominantly 4-acylisoxazolidines, whereas cycloaddition of the corresponding oximes afforded 5-iminoisoxazolidines. This inverse regioselection is due to HOMO activation by the oxime...
A dramatic effect of double bond configuration in N-oxy-3-aza Cope rearrangements—a simple synthesis of functionalised allenes
作者:Luis F.V. Pinto、Paulo M.C. Glória、Mário J.S. Gomes、Henry S. Rzepa、Sundaresan Prabhakar、Ana M. Lobo
DOI:10.1016/j.tetlet.2009.02.228
日期:2009.7
The first examples of low temperature N-oxy-3-aza Cope rearrangements, leading to functionalised allenes are described, where the Z-configuration of the enaminic double bond in the rearranging system proves critical.
thiyl radical to the alkynyl group followed by radical cyclization of the corresponding vinyl radical onto the O-silyloxime moiety to give cyclic O-silylhydroxylamines in good yields. The reactivity of O-silyloximes in radical cyclization was similar to or even higher than that of O-benzyloximes. Facile removal of the silyl group of the cyclization products leading to hydroxylamines and nitrone formation