Highly enantioselective intramolecular cyanoamidation: (+)-horsfiline, (-)-coerulescine, and (-)-esermethole.
The first asymmetric cyanoamidation with synthetically useful enantioselectivity (ee up to 99%) to produce 3,3-disubstituted oxindoles is reported. Palladium catalysts with chiral phosphoramidite ligands activate the cyanoformamide C-CN bond, which is subsequently functionalized with a tethered alkene to give all-carbon quaternary stereocenters. The use of the N,N-(i-Pr)(2) derivative of octahydro-MonoPhos allowed the production of oxindoles with high enantioselectivities. Cyanoformamides bearing free N-H groups are now tolerated, potentially allowing protecting-group-free synthesis. Oxindole products of cyanoamidation are rapidly transformed into (+)-horsfiline, (-)-coerulescine, and (-)-esermethole.
Reddy
Venkata Jaganmohan
VJ
Department of Chemistry, 207 Pleasant Street, SE, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Douglas
Christopher J
CJ