Efficient, microwave-assisted intramolecular 1,3-dipolar cycloadditions of oximes and <i>N</i>-methylnitrones derived from <i>o</i>-alkenylmethoxy-acetophenones
作者:Surinderjit Singh、M PS Ishar、Gajendra Singh、Rajinder Singh
DOI:10.1139/v05-049
日期:2005.3.1
stereoselective intramolecular 1,3-dipolar cycloadditions, both on microwave heating under solvent free conditions and refluxing in toluene, to afford novel cycloadducts (5a, 5b); the oxazepine-N-oxide (3a) reported to be formed in 98% yield was obtained only as a minor product (~10%). However, o-cinnamyloxy-acetophenone-oxime (2c) under similar conditions undergoes intramolecular N-alkylation to afford
与文献报道相反,邻烯丙氧基和巴豆氧基苯乙酮肟(2a,2b)转化为硝酮,在无溶剂条件下微波加热和回流下,硝酮进行区域和立体选择性分子内 1,3-偶极环加成在甲苯中,得到新的环加合物 (5a, 5b);据报道,以 98% 的产率形成的氧氮杂-N-氧化物 (3a) 仅作为次要产物 (~10%) 获得。然而,邻肉桂氧基-苯乙酮-肟 (2c) 在类似条件下进行分子内 N-烷基化以提供硝酮 (3c)。在微波辐射下进行的反应更清洁,反应时间更短,产率更高。N-甲基硝酮 (B) 的相应分子内 1,3-偶极环加成,