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
Enantioselective Synthesis of Nicotine via an Iodine-Mediated Hofmann–Löffler Reaction
作者:Estefanía Del Castillo、Kilian Muñiz
DOI:10.1021/acs.orglett.8b03909
日期:2019.2.1
An iodine-mediated Hofmann–Löffler reaction has been developed that enables the first enantioselective synthesis of nicotine based on this synthetic methodology. The effect of the free pyridine core on the involved electrophilic iodine reagents was explored in detail. The final synthesis proceeds under moderate reaction conditions that tolerate the free pyridine core. The same synthetic sequence is