Synthesis of spirocyclic azacycles from the cyclization of furan tethered N-acyliminium ions
作者:Sudhir R. Shengule、Anthony Willis、Stephen G. Pyne
DOI:10.1016/j.tet.2011.11.055
日期:2012.1
intermolecular reaction between 2a or 2b, via the nucleophilic C5 furan carbon, and their corresponding N-acyliminium ion intermediates. When the furan C5 position of 2b was blocked by substitution with bromine then TFA or Sc(OTf)3 catalysed cyclization reactions gave a spirotricyclic product (a 5-6-6-tricycle) in a highly diastereoselective manner. Cyclization of the analogous C5-Br-furan-pyrrolidone 29 with
质子酸和路易斯酸通过相应的N促进了拴系的呋喃-4,5-二羟基哌啶-2-酮,呋喃-4,5-二乙酰氧基哌啶-2-酮和呋喃-3,4-二乙酰氧基吡咯烷-2-酮的环化反应。-酰基酰亚胺离子中间体,已经被研究。在呋喃-4,5-二羟基哌啶-2-酮2a及其二乙酸酯衍生物2b的情况下,大环产物是由2a或2b之间的初始分子间反应,通过亲核C5呋喃碳及其相应的N-酰基亚胺鎓盐形成的。离子中间体。当2b的呋喃C5位置被溴取代时被TFA或Sc(OTf)3取代催化的环化反应以高度非对映选择性的方式产生了螺三环产物(5-6-6三环)。用TFA对类似的C5-Br-呋喃-吡咯烷酮29进行环化,产生了相关的螺三环(5-6-5三环)产物。尝试制备类似的氮杂环戊烷系统(5-7-5三轮车)的尝试并未成功。29的C5-PhS-呋喃-或C5-苯基磺酰基-吡咯烷酮类似物与TFA的环化反应也不成功。