This communication describes the utility of β‐amido allylboronate as a nucleophile in the catalytic amide allylation of N‐carbonyl imides. The reaction of the imide substrates with the boronates has been accomplished by using catalytic zinc bromide and basic additives (ethanol, potassium carbonate and 18‐crown 6‐ether), affording azaspiro‐γ‐lactones through a ring opening‐reclosure process with yields up to 100 %. The cost‐effective and easy‐to‐handle method established here tolerated for gram‐scale synthesis without significant loss of reaction efficiency.
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 β‐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 α‐methylene‐γ‐butyrolactone framework. In this communication, we report the successful development of a new catalytic system that enables enantioselective tin‐free “amide allylation” with the aid of a newly prepared (β‐amidoallyl)boronate for nucleophilic addition to isatins. This system consisting of a catalytic amount of diethylzinc 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.
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