Efficient Synthesis of Spiro[furan‐3,3′‐indoline] Derivatives via Reactions of Pyridinium Salts with Isatinylidene Acetoacetates

Abstract An efficient synthetic procedure for the functionalized spiro[furan‐3,3′‐indoline] derivatives was successfully developed by domino reactions of N ‐phenacylpyridinium bromides or N ‐ethoxycarbonylmethylenepyridinium bromide with isatinylidene acetoacetate in the presence of triethylamine in ethanol at room temperature. The mechanism included sequential Michael addition of the in situ generated pyridinium ylide and intramolecular substitution of enolate.