Disulfonimide‐Catalyzed Asymmetric Reduction of
<i>N</i>
‐Alkyl Imines
作者:Vijay N. Wakchaure、Philip S. J. Kaib、Markus Leutzsch、Benjamin List
DOI:10.1002/anie.201504052
日期:2015.9.28
A chiral disulfonimide (DSI)‐catalyzedasymmetric reduction of N‐alkyl imines with Hantzsch esters as a hydrogen source in the presence of Boc2O has been developed. The reaction delivers Boc‐protectedN‐alkyl amines with excellent yields and enantioselectivity. The method tolerates a large variety of alkyl amines, thus illustrating potential for a general reductive cross‐coupling of ketones with diverse
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。
作者:Maria H. T. Kwan、Jessica Breen、Martin Bowden、Louis Conway、Ben Crossley、Martin F. Jones、Rachel Munday、Nisha P. B. Pokar、Thomas Screen、A. John Blacker
DOI:10.1021/acs.joc.0c02617
日期:2021.2.5
crystal growth, and dissolution. A variety of cyclic and acyclic amine salts were resolved using mandelic acid (MA) and ditoluoyl tartaric acid (DTTA) with higher resolvability (S = yield × d.e.) than the simple diastereomericcrystallization alone. Comparing resolvabilities, resolutions were 1.6–44 times more effective with the R3 process than batch, though one case was worse. Further investigation of this
已经开发出一种新的动态非对映异构结晶方法,其中连续分离母液,在固定床催化剂上外消旋,然后通过拆分-消旋-再循环(R 3)过程再循环到结晶器中。将消旋化与结晶化分离克服了原位使用催化剂的问题,这些催化剂遭受一系列条件,抑制和分离的冲突。通过[IrCp * I 2 ] 2的共价连接实现了连续消旋SCRAM催化剂以王氏树脂为固体载体,得到固定床催化剂。一种高级和多种仲级光学富集的胺已高效消旋,其停留时间与结晶相适应(2.25–30分钟)。该催化剂显示出比均相类似物更低的周转率(TOF),但重复使用显示出长寿命(例如40次循环,190小时),给出了可接受的周转数(TON)(最高4907)。发现在N-甲胺外消旋过程中甲胺的缓慢释放使催化剂失活,可以使用氢碘酸将其部分活化。R 3中实现了动态结晶通过不断去除溶解度较高的非对映异构体并提供溶解度较低的非对映异构体来完成这一过程。确定了非对映异构体的溶解度
Fe(BF4)2·6H2O/2,6-pyridinedicarboxylic acid catalysed nitrosation of a wide variety of substituted styrenes has been developed in the presence of t-BuONO/NaBH4 under H2 pressure (10 bar) in MeOH–H2O (5 : 1) to afford corresponding oximes in good to excellent yields.
High-Valent Pentamethylcyclopentadienylcobalt(III) or -iridium(III)-Catalyzed CH Annulation with Alkynes: Synthesis of Heterocyclic Quaternary Ammonium Salts
作者:Ye-Xing Lao、Shang-Shi Zhang、Xu-Ge Liu、Chun-Yong Jiang、Jia-Qiang Wu、Qingjiang Li、Zhi-Shu Huang、Honggen Wang
DOI:10.1002/adsc.201600194
日期:2016.6.30
Nine types of diversely fused heterocyclic quaternaryammoniumsalts were constructed through an oxidative CH annulation reaction. Both high‐valent pentamethylcyclopentadienylcobalt(III) and pentamethylcyclopentadienyliridium(III) were found to be effective as catalyst for this reaction. Broad substrate scope and good functional group tolerance were observed.