Convenient preparation of synthetically useful chiral quaternary carbon-containing bicyclic compounds with organocatalysts
作者:Yuichiro Kawamoto、Naoki Noguchi、Daiki Ozone、Toyoharu Kobayashi、Hisanaka Ito
DOI:10.1016/j.tetlet.2021.153495
日期:2021.11
Chiral quaternary carbon-containing bicyclic compounds possessing carbonyl functionalities were efficiently synthesized through asymmetric intramolecular aldol reactions with organocatalysts. Bicyclo [3.3.0] and [3.4.0] systems were constructed with a diamine catalyst, while bicyclo [4.3.0] and [4.4.0] skeletons were prepared by an acylsulfonamide type catalyst.
Enantioselective Synthesis of α,α-Disubstituted Cyclopentenes by an <i>N</i>-Heterocyclic Carbene-Catalyzed Desymmetrization of 1,3-Diketones
作者:Manabu Wadamoto、Eric M. Phillips、Troy E. Reynolds、Karl A. Scheidt
DOI:10.1021/ja073987e
日期:2007.8.1
The enantioselective synthesis of α,α-disubstituted cyclopentenes using N-heterocyclic carbene catalysis is reported. This desymmetrization reaction proceeds via a chiral enol generated in situ from the combination of an enantiopure azolium salt and α,β-unsaturated aldehyde. This reactive enol undergoes addition to one of two enantiotopic ketones to afford an optically active β-lactone after the intermediate
报道了使用 N-杂环卡宾催化对映选择性合成 α,α-二取代环戊烯。这种去对称化反应是通过对映纯的唑鎓盐和 α,β-不饱和醛的组合原位产生的手性烯醇进行的。在中间体甲醇参与内部酰化事件以释放卡宾催化剂后,该反应性烯醇与两种对映体酮之一发生加成以提供光学活性 β-内酯。在 R = 芳基的底物中,在内酯形成后立即发生脱羧作用,以产生高达 96% ee 的含季中心环戊烯产物。当 R 基团是烷基时,β-内酯以中等产率和高非对映选择性和对映选择性分离。
Organocatalytic enantioselective desymmetrization of enal-tethered cyclohexane-1,3-diones
作者:Lakshmi Revati Magham、Abdus Samad、Satish B. Thopate、Jagadeesh Babu Nanubolu、Rambabu Chegondi
DOI:10.1039/d4cc00487f
日期:——
Organocatalytic asymmetric desymmetrization of prochiral cyclohexane-1,3-diones has been demonstrated through the merging of iminium and enamine activation. The tandem annulation reaction proceeds through a sequential oxa-Michael addition/intramolecular aldol reaction/[1,3]-amino oxetane rearrangement pathway. Mechanistic study using an 18O-water experiment suggests oxetane rearrangement instead of