Deactivation mechanisms of iodo-iridium catalysts in chiral amine racemization
作者:Maria H.T. Kwan、Nisha P.B. Pokar、Catherine Good、Martin F. Jones、Rachel Munday、Thomas Screen、A. John Blacker
DOI:10.1016/j.tet.2020.131823
日期:2021.1
The homogenous, [IrCp∗I2]2, SCRAM catalyst (1) is active in the racemization of chiral amines. NMR, kinetic and structural mechanistic studies have determined the cause of catalyst deactivation to occur when ammonia or methylamine are liberated by hydrolysis or aminolysis of the intermediate imine, which tightly coordinate to the iridium centre to block turnover. Control of moisture and substrate concentration
均相的[IrCp * I 2 ] 2 SCRAM催化剂(1)在手性胺的外消旋中具有活性。NMR,动力学和结构机理研究已确定了当中间体亚胺的水解或氨解释放氨或甲胺而释放出氨或甲胺时,催化剂失活的原因,该中间体或亚胺与铱中心紧密配合,从而阻止了周转。控制水分和底物浓度可以抑制失活,同时用氢碘酸鉴定废催化剂的部分再活化。
A Practical Electrophilic Nitrogen Source for the Synthesis of Chiral Primary Amines by Copper-Catalyzed Hydroamination
作者:Sheng Guo、Jeffrey C. Yang、Stephen L. Buchwald
DOI:10.1021/jacs.8b10564
日期:2018.11.21
and practical method for the catalytic installation of the amino group across alkenes and alkynes has long been recognized as a significant challenge in synthetic chemistry. As the direct hydroamination of olefins using ammonia requires harsh conditions, the development of suitable electrophilic aminating reagents for formal hydroamination methods is of importance. Herein, we describe the use of 1
route to β-enamino esters 1, using accessible starting materials, was developed. Lithiated enamines are allowed to react with diethyl carbonate or benzyl chloroformate with the formation of the β-enamino esters 1a or 1b. The reaction is rather general from a wide array of ketimines and aldimines. Products included cyclic β-enamino esters 1aa-ac, very useful for the synthesis of natural products.
Enantioselective Intramolecular α‐Arylation of Benzylamine Derivatives: Synthesis of a Precursor to Levocetirizine
作者:Rakesh K. Saunthwal、Maria Schwarz、Rajendra K. Mallick、William Terry‐Wright、Jonathan Clayden
DOI:10.1002/anie.202216758
日期:2023.3.27
The deprotonation of N′-aryl urea derivatives with a chiral lithium amide base leads to an enantioselective C-arylation of benzylamines. An unusual stereoretentive substitution reaction followed by N-deprotection of the urea forms diarylmethylamine derivatives, including a synthetic intermediate en route to the drug levocetirizine.