Solvent‐Controlled Divergent Cyclization of 3‐Ylideneoxindoles with Ethyl 2‐Diazoacetate: Access to Spirocyclopropyl and Spiropyrazolines Oxindoles

Herein a catalyst‐free solvent‐controlled method for the divergent synthesis of spirocyclopropyl and spiropyrazoline oxindoles from 3‐ylideneoxindoles and ethyl diazoacetate was developed. With ClCH2CH2Cl as the solvent, spirocyclopropyl oxindoles were obtained in moderate to excellent yields, whereas the use of MeOH as solvent afforded spiropyrazoline oxindoles in moderate to good yields. The readily available substrates, simple operation and various product transformations further highlighted the utility of this method. A catalyst‐free solvent‐controlled method for the divergent synthesis of spirocyclopropyl and spiropyrazoline oxindoles in high yields and with excellent diastereoselectivities from 3‐ylideneoxindoles and ethyl diazoacetate is reported. Moreover, an oxidation protocol that allow the preparation of spiropyrazole oxindoles from spiropyrazoline oxindoles is also developed. The readily available substrates, simple operation and various product transformations further highlighted the utility of this method.