Synthesis of novel bicyclic nitrogen heterocycles by the intramolecular dipolar cycloaddition reaction of nitrones with allenes and alkynes
作者:Albert Padwa、Michael Meske、Zhijie Ni
DOI:10.1016/0040-4020(94)00966-x
日期:1995.1
formed was identified as 4-methyl-2,5-endo-oxo-2,3,4,5-tetrahydro[1,4]benzoxazepin. The formation of this novel rearranged product involves an initial dipolar cycloaddition across the acetylenic π-bond to give the expected 4-isoxazoline as a transient intermediate. The next step proceeds by homolysis of the O-N linkage and this is followed by ring closure to produce an aziridine which undergoes further
一系列烯丙基和炔基硝酮的分子内偶极环加成反应的研究已经进行。苯羟胺容易与邻-(1,2-丙二烯氧基)苯甲醛反应生成二氧杂氮杂双环[3.2.1]辛烯。还研究了2-(1,2-丙炔氧基)苯甲醛与N-甲基羟胺的分子内3 + 2-环加成反应。在这种情况下,形成的主要环加合物被鉴定为4-甲基-2,5-内-oxo-2,3,4,5-四氢[1,4]苯并x庚因。这种新颖的重排产物的形成涉及跨越乙炔π键的初始偶极环加成,以产生预期的4-异恶唑啉作为过渡中间体。下一步通过ON键的均质化进行,然后进行环闭合以产生氮丙啶,该氮丙啶经历进一步的CC键裂解。借助于邻-醌甲基化物中间体将所得的甲亚胺叶立德转化为最终的重排产物。还发现苯磺酰基活化的烯与烷基羟胺反应得到硝酮,该硝酮与相邻的π键进行环加成反应,得到所得的双环氮杂环。