A highly efficient asymmetric hydrogenation of cyclicimines containing a pyridyl moiety was established by using iridium catalysts with chiral spiro phosphine-oxazoline ligands. This process will facilitate the development of new nicotine-related pharmaceuticals. The introduction of a substituent at the ortho position of the pyridyl ring to reduce its coordinating ability ensures the success of the
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