Alkynylation of Isatin Derivatives Catalyzed by a Silver-Chiral Quaternary Ammonium Salt Derived from Quinine

Asymmetric addition of terminal alkynes catalyzed bya transitionmetal to isatins obviously is an efficient and economic method forthe synthesis of 3-alkynyl-3-hydroxy-2-oxindoles. The new dimericchiral quaternary ammoniums derived from a natural chiral alkaloid,quinine, can be used as cationic inducers of the enantioselectivityfor the Ag-(I)-catalyzed alkynylation of isatin derivatives under mildconditions. The desired chiral 3-alkynyl-3-hydroxy-2-oxindoles canbe obtained in good to high yields with high to excellent enantioselectivites(<= 99% ee). A variety of aryl-substituted terminal alkynes andsubstituted isatins are tolerated in this reaction.

Automated summary

The asymmetric addition of terminal alkynes catalyzed by a transition metal to isatins is an efficient and economical method for synthesizing 3-alkynyl-3-hydroxy-2-oxindoles. Using a new dimeric chiral quaternary ammonium derived from quinine as the cationic inducer, under mild conditions, the desired chiral compounds can be obtained in good to high yields with high enantioselectivity (<= 99% ee), and a variety of aryl-substituted terminal alkynes and substituted isatins are tolerated in this reaction.