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)