A facile oxime–nitrone isomerization through the 1,2-hydrogenshift in 4-oxo-4H-pyrido[1,2-a]pyrimidine-3-carbaldehyde oximes is discussed. The resultant NH-nitrones are trapped by maleimides to afford intermolecular cycloadducts. The reaction of the oximes with electron-deficient acetylenes undergoes via another path initiated by a nucleophilic attack of the oxime to acetylene moiety.
讨论了一种通过4-氧代-4 H-吡啶并[1,2 - a ]嘧啶-3-甲醛肟的1,2-氢转移反应实现的肟-硝酮的异构化反应。所得的NH-硝酮被马来酰亚胺捕获,以提供分子间的环加合物。肟与缺电子乙炔的反应通过另一种途径进行,该途径由肟对乙炔部分的亲核攻击而引发。
Generation of NH-azomethine imine intermediates through the 1,2-hydrogen shift of hydrazones and their intermolecular cycloaddition reaction with olefinic dipolarophiles
The thermal 1,2-hydrogenshift of the hydrazone generates the NH-azomethine imine intermediate in the 4-oxo-4H-pyrido[1,2-a]pyrimidine-3-carbaldehyde system under mild conditions. Therein, the resulting NH-azomethine imine should be stabilized by forming an internal hydrogen bond with the carbonyl oxygen at the 4-position. Its smooth stereoselective intermolecular cycloaddition reaction with olefinic
mild的热1,2-氢转移在温和条件下在4-氧代-4 H-吡啶并[1,2 - a ]嘧啶-3-甲醛体系中生成NH-偶氮甲亚胺亚胺中间体。其中,应通过在4-位与羰基氧形成内部氢键来稳定所得的NH-偶氮甲亚胺。讨论了其与烯烃双极性亲和剂的平滑的立体选择性分子间环加成反应,得到吡唑烷衍生物。