Borane-Catalyzed Direct Asymmetric Vinylogous Mannich Reactions of Acyclic α,β-Unsaturated Ketones
作者:Jun-Jie Tian、Ning Liu、Qi-Fei Liu、Wei Sun、Xiao-Chen Wang
DOI:10.1021/jacs.1c00006
日期:2021.3.3
Herein, we report that, by using chiral bicyclic bisborane catalysts, we have achieved the first highly regio-, diastereo-, and enantioselective direct asymmetric vinylogous Mannich reactions of acyclic α,β-unsaturatedketones. The strong Lewis acidity and steric bulk of the bisborane catalysts were essential for the observed high yields and selectivities.
A catalytic asymmetric vinylogous Mannich-type reaction of γ-halo-α,β-unsaturated N-acylpyrazoles and N-Boc-aldimines was disclosed, which afforded an array of halogenated (F-, Cl-, and Br-) allylic stereogenic carbon centers in high yields with good to high regio-, diastereo-, and enantioselectivities. The brominated product served as a suitable electrophile for common SN2 nucleophilic substitution
Strategy for Stereoselective Metal-free α-Functionalization of 2-Azaaryl Acetates with <i>N</i>
-Boc Imines
作者:Iñaki Bastida、Marcos San Segundo、Rosa López、Claudio Palomo
DOI:10.1002/chem.201703748
日期:2017.9.27
We report the first diastereo‐ and enantioselective formal Mannich reaction of 2‐pyridyl acetates which gives rise to α‐ and β‐functionalized 2‐substituted pyridines. Key for success is the previous azaarene N‐oxide formation enabling α‐carbon deprotonation by a mild bifunctional Brønsted base and subsequent reaction with N‐Boc imines under almost perfect stereocontrol.
Organocatalytic Nucleophilic Addition of Hydrazones to Imines: Synthesis of Enantioenriched Vicinal Diamines
作者:Yang Wang、Qian Wang、Jieping Zhu
DOI:10.1002/anie.201702295
日期:2017.5.8
catalytic amount of chiral phosphoric acid, nucleophilicaddition of N‐monosubstituted hydrazones to N‐Boc imines affords differentially protected vicinal diamines in the form of β‐amino N,N′‐dialkyldiazenes in excellent yields with high chemo‐, diastereo‐, and enantioselectivity. This catalytic asymmetric aza‐Mannich reaction represents the first example in which N‐alkyl hydrazones serve as α‐azo carbanion
Borane-Catalyzed C3-Alkylation of Pyridines with Imines, Aldehydes, or Ketones as Electrophiles
作者:Zhong Liu、Jia-Hao He、Ming Zhang、Zhu-Jun Shi、Han Tang、Xin-Yue Zhou、Jun-Jie Tian、Xiao-Chen Wang
DOI:10.1021/jacs.2c00962
日期:2022.3.23
The existing methods, including electrophilic aromatic substitution and C–H activation, often require harsh reaction conditions and excess pyridine and generate multiple regioisomers. Herein, we report a method for borane-catalyzed tandem reactions that result in exclusively C3-selective alkylation of pyridines. These tandem reactions consist of pyridine hydroboration, nucleophilicaddition of the resulting