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。
Chemoselective Oxidative Spiroetherification and Spiroamination of Arenols Using I<sup>+</sup>/Oxone Catalysis
We developed a chemoselective oxidative dearomative spiroetherification and spiroamination of arenols using I+/oxone catalysis. The intramolecular dearomative C-O and C-N couplings proceeded much more efficiently under slightly acidic conditions to give the corresponding spiro adducts in higher yields compared with previous methods using transition metal or hypervalent iodine catalysts. Control experiments
Direct halogenative dearomatization of 2-naphthols by NXS (X = Cl, Br) in water
作者:Zhenbei Zhang、Qiangsheng Sun、Daqian Xu、Chungu Xia、Wei Sun
DOI:10.1039/c6gc01673a
日期:——
A direct halogenative dearomatization of substituted 2-naphthols was achieved by NXS (X = Cl, Br) in environmentally friendly water at room temperature.
reported. Furthermore, several other halophenols (X = Cl, I) were also tolerated in this process. Control experiments reveal a dearomative Michael addition of phenols at their halogenated positions to methylenemalonates, followed by intramolecular radical-based SRN1 dehalogenative cyclopropanation. However, according to the density functional theory (DFT) calculations, an SN2 dehalogenative cyclopropanation
报道了对溴苯酚与活化烯烃(亚甲基丙二酸酯)的碱辅助脱芳[2 + 1]螺环化,以构建各种环丙基螺环己二烯酮骨架。此外,在此过程中还可以耐受其他几种卤代酚(X = Cl,I)。对照实验揭示了苯酚在其卤化位置上发生脱芳香迈克尔加成反应,形成亚甲基丙二酸酯,然后进行基于分子内自由基的 S RN 1 脱卤环丙烷化。然而,根据密度泛函理论(DFT)计算,不应排除具有相同低活化能势垒的S N 2 脱卤环丙烷化。该方法的实用性通过脱芳构化产物的克级合成和转化来展示。
Ammonium Hypoiodite-Catalyzed Peroxidative Dearomatization of Phenols
Here, we report the first transition metal-free peroxidative dearomatization of phenols using hypoiodite catalysis with TBHP. Hypoiodite salts are generated in situ from the corresponding quaternary ammonium iodides in the presence of TBHP, and the oxidative coupling reaction proceeds efficiently under mild conditions. The dearomatized products are versatile synthetic intermediates for further synthetic transformations to various complex structures including heterocycles. As a demonstration, the further oxidation of the unsaturated peroxide with TBHP afforded the corresponding peroxy epoxide in good yield.