Diastereodivergent synthesis of fully disubstituted spiro[indoline-3,2’-pyrrolidin]-2-ones via tuneable Lewis base/Bronsted base-promoted (3 + 2) cycloadditions

摘要

Herein we report a diastereodivergent synthesis of fully disubstituted spiro[indoline-3,2’-pyrrolidin]-2- ones through base-promoted (3 + 2) cycloadditions. Importantly, the catalysts are found to have full control over the configuration of the stereocenters. When a Lewis base (PCy3) is used as a catalyst, good yields and excellent diastereoselectivities are obtained, regardless of the properties of the substituents, whereas spiro[indoline-3,2’-pyrrolidin]-2-ones of a different diastereoisomer are produced in good yields when a Bronsted base (K2CO3) is used. ESI-MS experiments proved the existence of key zwitterionic intermediates.