Synthesis of Dispirocyclopentyl‐3,3′‐bisoxindoles via Domino Cycloaddition Reactions of 4‐Dimethylaminopyridinium Bromides with 3‐Phenacylideneoxindoles

Abstract

Abstract The base mediated cycloaddition reactions of 4‐dimethylamino‐1‐phenacylpyridinium bromides with two molecular 3‐phenacylideneoxindoles in methylene dichloride afforded functionalized dispirocyclopentyl‐3,3′‐bisoxindoles in good yields and with high diastereoselectivity. The similar cycloaddition reactions of 1‐( N , N ‐dialkylcarbamoylmethyl) and 1‐cyanomethyl 4‐dimethylamino‐pyridinium bromide in refluxing ethanol in the presence of triethylamine also resulted in dispirocyclopentyl‐3,3′‐bisoxindoles with high diastereoselectivity. The stereochemistry of dispirocyclopentyl‐3,3′‐bisoxindoles was elucidated on the basis of 1 H NMR data and single crystal structures.