<i>N</i>,<i>N</i>′-Dioxide/Gd(OTf)<sub>3</sub> Complex-Promoted Asymmetric Aldol Reaction of Silyl Ketene Imines with Isatins: Water Plays an Important Role
A highly diastereo- and enantioselective aldol reaction of isatins with silyl ketene imines was realized by using a chiral N,N′-dioxide/GdIII complex (1 mol %), and with the addition of water, all the reactions completed within 10 min and various β-hydroxy nitriles with adjacent tetrasubstituted stereocenters were obtained in excellent outcomes. The essential role of water was probed, and a possible
A Catalytic Asymmetric Ring‐Expansion Reaction of Isatins and α‐Alkyl‐α‐Diazoesters: Highly Efficient Synthesis of Functionalized 2‐Quinolone Derivatives
Asymmetricexpansion: A catalyticasymmetricring‐expansionreaction of the title compounds occurs in the presence of a Sc(OTf)3 catalyst bearing an N,N′‐dioxide‐based ligand. Highlyfunctionalized2‐quinolonederivatives containing a chiral C4‐quaternary stereocenter were obtained in high yields and high levels of selectivity under mild reaction conditions (see scheme; Tf=trifluoromethanesulfonyl)
The first catalytic asymmetrichetero-Diels-Alderreaction of Brassard'sdienes with isatins was realized using Mg(II)/N,N'-dioxide complexes as catalysts, affording the corresponding chiral spirolactones bearing tetrasubstituted centers in up to 99% yield with up to 99% ee and >99 : 1 dr within 3 hours. In the mechanism, based on the operando IR experiments, a predominant Diels-Alder pathway was found