Stereochemistry and Mechanistic Insight in the [2<sup>k</sup>+2<sup>i</sup>+2<sup>i</sup>] Annulations of Ketenes and Imines
作者:Zhanhui Yang、Wei He、Baoxiang Cheng、Jiaxi Xu
DOI:10.1021/acs.joc.6b00279
日期:2016.6.3
products due to the occurrence of the stepwise nucleophilic annulation. However, in the [2k+2i+2i] annulations of seven-membered cyclic imine dibenzo[b,f][1,4]oxazepine, the zwitterionic aza-butadiene-type intermediates exclusively undergo exo hetero-Diels–Alder cycloadditions with another molecule of imine to yield (2,4)-trans-(4,5)-trans-[2k+2i+2i] annuladducts stereospecifically, regardless of the ketene
以六元3,4-二氢异喹啉为亚胺探针,研究了一个烯酮分子与两个亚胺分子的环化反应[[2 k +2 i +2 i ]的环化反应中的立体化学和机理。提出了一种协同的杂Diels-Alder环加成机理来解释立体化学结果。在大多数情况下,从烯酮和亚胺生成的两性离子2-氮杂-1,3-丁二烯型中间体会与第二个亚胺分子发生内杂-Diels -Alder环加成反应。对于带有给电子取代基的烯酮,(2,4)-顺式-(4,5)-顺式-[2 k +2 i +2 i]年环化合物是立体定向形成的,而对于带有电子接受取代基的烯酮,(2,4)-顺式-(4,5)-反式-[2 k +2 i +2 i ]年环化合物是立体定向生成的。芳氧基烯酮和3,4-二氢异喹啉的[2 k +2 i +2 i ]环由于逐步的亲核环化而产生立体发散产物。然而,在[2 ķ 2我2我] 7元环亚胺二苯并annulations [ b,˚F] [1,4]