DMAP‐Catalyzed Diastereoselective [3+2] Annulation of Isatin‐Derived MBH Carbonates and 3‐Methyleneoxindoles: Tempting Two Adjacent Quaternary Spirocenters

Abstract

A highly diastereoselective synthesis of bis‐spirooxindoles has been achieved via a [3+2] annulation reaction using MBH carbonates with 3‐methyleneoxindoles. By utilizing DMAP (20 mol%) as an organocatalyst under mild reaction conditions, a versatile bis‐spirooxindole has been synthesised in good to high yield (up to 93%) and excellent diastereoselectivities (up to >20:1). The robustness of this methodology is demonstrated through scale‐up experiments and straightforward post‐synthetic transformations. Moreover, based on the reaction result, a plausible reaction mechanism is proposed.