Enantioselective nucleophilic addition to N-(2-pyridylsulfonyl)imines by use of dynamically induced chirality

Pd(OAc)2-catalyzed asymmetric hydrogenation of sterically hindered N-tosylimines

Asymmetric hydrogenation of sterically hindered substrates still constitutes a long-standing challenge in the area of asymmetric catalysis. Herein, an efficient palladium acetate (an inexpensive Pd salt with low toxicity) catalyzed asymmetric hydrogenation of sterically hindered N-tosylimines is realized with high catalytic activities (S/C up to 5000) and excellent enantioselectivities (ee up to 99.9%). Quantum chemical calculations suggest that uniformly high enantioselectivities are observed due to the structurally different S- and R-reaction pathways.

Sterically hindered unsaturated compounds are challenging substrates for asymmetric hydrogenation. Here, the authors report a palladium/chiral (bis)phosphine catalytic system that hydrogenates a number of hindered N-tosylimines with excellent enantioselectivitites.

Copper(I)-Fesulphos Lewis Acid Catalysts for Enantioselective Mannich-Type Reaction of N-Sulfonyl Imines

[reaction: see text] Copper(I) complexes of Fesulphos ligands are efficient chiral Lewis acid catalysts in the Mannich-type addition of silyl enol ethers of ketones, esters, and thioesters to N-(2-thienyl)sulfonyl aldimines. The corresponding optically active beta-amino carbonyl derivatives were obtained in good yields (58-91%) and with moderate to good enantioselectivity (61-93% ee). Removal of the N-activating group was achieved under mild conditions by simple treatment of the products with Mg in methanol.