Synthesis of Piperazinones, Piperazines, Tetrahydropyrazines, and Dihydropyrazinones from Polymer-Supported Acyclic Intermediates via N-Alkyl- and N-Acyliminiums
作者:Barbora Vaňková、Lucie Brulíková、Boyuan Wu、Viktor Krchňák
DOI:10.1002/ejoc.201200591
日期:2012.9
procedure from easily accessible polymer-supported acyclic precursors containing either a masked aldehyde or ketone group. Acid-mediated unmasking of the aldehyde triggered cyclic iminium formation followed by reduction with triethylsilane present in the cleavage cocktail. The effect of the substituent at the iminium-forming nitrogen was evaluated: whereas complete conversion to the target compounds was
三取代的哌嗪酮、哌嗪、四氢吡嗪和二氢吡嗪酮通过一步法从含有掩蔽醛或酮基团的聚合物支撑的无环前体中制备。酸介导的醛的暴露引发了环状亚胺的形成,然后用裂解混合物中存在的三乙基硅烷进行还原。评估了亚胺形成氮上取代基的影响:虽然观察到 N-烷基、芳基和苯磺酰胺衍生物完全转化为目标化合物,但 N-酰基化合物的醛部分还原为醇. 类似地,酮容易为环状亚胺提供 N-烷基化合物,而它们与 N-酰基前体的环化则不情愿地进行。有趣的是,在三乙基硅烷的存在下,在 60 °C 下树脂结合的无环前体的裂解导致酰胺键分解并形成内酯。类似的合成路线也成功地用于制备哌嗪,并作为合成二氮杂卓的替代路线进行了测试。