Tandem Conjugate Additions and 3-Aza-Cope Rearrangements of Tertiary Allyl Amines and Cyclic α-Vinylamines with Acetylenic Sulfones. Applications to Simple and Iterative Ring Expansions Leading to Medium and Large-Ring Nitrogen Heterocycles
作者:Mitchell H. Weston、Katsumasa Nakajima、Thomas G. Back
DOI:10.1021/jo800600a
日期:2008.6.1
Tertiary acyclic allyl amines and tertiary cyclic α-vinyl amines undergo conjugate additions to acetylenic sulfones to produce zwitterion intermediates, followed by 3-aza-Cope rearrangements. In the case of cyclic α-vinyl amines, the process results in ring-expansion, providing a novel route to 9- to 17-membered cyclic amines. The Hammett plot for the reaction of 8b with 2a−2f shows ρ = +1.19, which
叔无环烯丙基胺和叔环α-乙烯基胺经过共轭加成反应到炔属砜上,生成两性离子中间体,然后进行3-氮杂-Cope重排。在环状α-乙烯基胺的情况下,该过程导致扩环,为9至17元环状胺提供了新颖的途径。8b与2a - 2f反应的哈米特图显示ρ= +1.19,这与速率确定步骤中拟议的两性离子的形成是一致的,其中在芳基磺酰基部分的吸电子取代基稳定了负电荷并增强了反应速度。在11种情况下,在甲醇中观察到了其他途径,其中甲氧基取代基通过稳定的烯丙基阳离子促进相应两性离子的解离机理,而衍生自胺12的两性离子通过甲醇直接攻击应变的叠氮鎓部分而不是通过重排而经历开环。开发了一个迭代过程,其中一个扩环的产物转化为新的环状α-乙烯基胺,然后重复缀合物加成和[3,3]重排。该方案通过其在莫托帕明A和B的合成中的应用得到了说明。