Departamento de Química Orgánica, Universidad de Valencia, Dr. Moliner 50, E-46100 Burjassot, Valencia, Spain.
Org Biomol Chem. 2010 Nov 7;8(21):4884-91. doi: 10.1039/c0ob00088d. Epub 2010 Aug 26.
The N-heterocyclic carbene (NHC) catalyzed addition of enals to enones to yield trans-cyclopentenes has been investigated using DFT methods at B3LYP/6-31G** computational level. This NHC catalyzed reaction comprises several steps. The first one is the formation of a Breslow intermediate, which nucleophilically attacks to the conjugated position of the enone to yield an enol-enolate. This second step is responsible for the trans relationship at the final cyclopentene. An intramolecular aldolic condensation allows for the formation of the alkoxy cyclopentane intermediate, that by intramolecular nucleophilic attack on the carbonyl group yields a bicyclic ether. The extrusion of the NHC catalyst affords a bicyclic lactone, yielding by CO(2) elimination, the final trans-cyclopentene.
使用 B3LYP/6-31G**计算水平的密度泛函理论（DFT）方法研究了 N-杂环卡宾（NHC）催化的烯醛与烯酮加成反应生成反式环戊烯。该 NHC 催化反应包括几个步骤。第一步是 Breslow 中间体的形成，它亲核攻击烯酮的共轭位置，生成烯醇-烯醇化物。第二步负责最终环戊烯的反式关系。分子内羟醛缩合允许形成烷氧基环戊烷中间体，该中间体通过对羰基的分子内亲核进攻生成双环醚。NHC 催化剂的脱除得到双环内酯，通过 CO(2)消除生成最终的反式环戊烯。
