A new thiourea catalyst is reported for the enantioselective cationic polycyclization of hydroxylactams. Both the yield and enantioselectivity of this transformation were found to vary strongly with the identity of a single aromatic residue on a common catalyst framework, with more expansive and polarizable arenes proving optimal. Evidence is presented for a mechanism in which stabilizing cation-Pi interactions are a principal determinant of enantioselectivity.
A new thiourea catalyst is reported for the enantioselective cationic polycyclization of hydroxylactams. Both the yield and enantioselectivity of this transformation were found to vary strongly with the identity of a single aromatic residue on a common catalyst framework, with more expansive and polarizable arenes proving optimal. Evidence is presented for a mechanism in which stabilizing cation-Pi interactions are a principal determinant of enantioselectivity.
Zinc‐Catalyzed Asymmetric Hydrosilylation of Cyclic Imines: Synthesis of Chiral 2‐Aryl‐Substituted Pyrrolidines as Pharmaceutical Building Blocks
作者:Izabela Węglarz、Karol Michalak、Jacek Mlynarski
DOI:10.1002/adsc.202001043
日期:2021.3.2
cyclic imines promoted by a chiral zinc complex is reported. In situ generated zinc‐ProPhenol complex with silane afforded pharmaceutically relevant enantioenriched 2‐aryl‐substituted pyrrolidines in high yields and with excellent enantioselectivities (up to 99% ee). The synthetic utility of presented methodology is demonstrated in an efficient synthesis of the corresponding chiral cyclic amines, being pharmaceutical
Enantioselective Imine Reduction Catalyzed by Phosphenium Ions
作者:Travis Lundrigan、Erin N. Welsh、Toren Hynes、Chieh-Hung Tien、Matt R. Adams、Kayelani R. Roy、Katherine N. Robertson、Alexander W. H. Speed
DOI:10.1021/jacs.9b07293
日期:2019.9.11
The first use of phosphenium cations in asymmetric catalysis is reported. A diazaphosphenium triflate, prepared in two or three steps on a multi-gram scale from commercially available materials catalyzes the hydroboration or hydrosilation of cyclic imines with enantiomeric ratios of up to 97:3. Catalyst loadings are as low as 0.2 mole percent. Twenty-two aryl/heteroaryl pyrrolidines and piperidines