A novel [4+1] spiroannulation of o‐ & p‐bromophenols with α,β‐unsaturated imines has been developed for the direct synthesis of a new family of azaspirocyclic molecules. Notably, several other halophenols (X=Cl, I) were also applicable for this transformation. Moreover, a catalytic asymmetric version of the reaction was realized with 1‐bromo‐2‐naphthols by using a chiral ScIII/Py‐Box catalyst. Mechanistic
已经开发了一种新颖的[4 + 1]邻和对溴苯酚与α,β-不饱和亚胺螺环合成的方法,用于直接合成新的氮杂螺环分子家族。值得注意的是,其他几种卤代酚(X = Cl,I)也适用于该转化。此外,通过使用手性Sc III / Py-Box催化剂,使用1-溴-2-萘酚实现了反应的催化不对称形式。机理研究表明,该多米诺反应是通过苯酚衍生物在其卤代位置的亲电触发的脱芳香化作用进行的,然后通过基于自由基的S RN 1机理用N-亲核试剂进行卤素置换。
PPh<sub>3</sub>-Catalyzed Reactions of Alkyl Propiolates with<i>N</i>-Tosylimines: A Facile Synthesis of Alkyl 2-[aryl(tosylimino)methyl]acrylate and an Insight into the Reaction Mechanism
A new PPh3‐catalyzed synthesis of alkyl2‐[aryl(tosylimino)methyl]acrylates from propiolate and N‐tosylimine has been developed. Deuterium‐labelling experiments show that the reaction mechanism involves several hydrogen‐transfer processes, which are not the turnover‐limiting step and strongly rely on the nature of the reaction media. The stable phosphonium–enamine zwitterion, which was proven to play
Bifunctional Organocatalytic Strategy for Inverse-Electron-Demand Diels-Alder Reactions: Highly Efficient In Situ Substrate Generation and Activation to Construct Azaspirocyclic Skeletons
作者:Xianxing Jiang、Xiaomei Shi、Shoulei Wang、Tao Sun、Yiming Cao、Rui Wang
DOI:10.1002/anie.201107716
日期:2012.2.27
highly enantioselective organocatalytic version of the title reactionusing an in situ substrate generation/activation catalytic mode is described (see scheme). The reaction provides an efficient enantioselective construction of functionalized azaspirocyclic skeletons. The in situgeneration of the enolate provides a new way in which to use this important nucleophile in organic synthesis.
We developed novel shackled P-chiral ligands based on 1-phosphanorbornenes and oxazolines. They were subsequently evaluated in palladium-catalyzed (4+2) annulations, producing enantioenriched tetrahydropyran scaffolds in good yields with high site selectivity and enantioselectivity. Moreover, chemoselective (4+4) products were also achieved by using acyclic imines. In addition, density functional theory