Use of a (β-Amidoallyl) boronate as a Nucleophilic Reagent in Catalytic Enantioselective Addition to Isatins

Spirocycles are attractive synthetic targets for many synthetic chemists owing to their potent and promising biological activities. We previously reported a method for the highly enantioselective allylation of various isatins with beta-amido-functionalized allylstannanes under the influence of indium-based chiral catalysts and applied this method to the synthesis of 2-oxindole derivatives spiro-fused to an alpha-methylene-gamma-butyrolactone framework. In this communication, we report the successful development of a new catalytic system that enables en-antioselective tin-free "amide allylation" with the aid of a newly prepared (beta-amidoallyl) boronate for nucleophilic addition to isatins. This system consisting of a catalytic amount of diethyl-zinc as a competitive candidate in the presence of chiral 1,3-amino alcohols incorporating an acidic phenol functionality offers new opportunities for environmentally benign access to medicinally relevant spirocyclic 2-oxindoles.