4-(N,N-Dimethylamino)pyridine (DMAP)-Catalyzed 1,3-Dipolar Cycloaddition of 3-Aminooxindole-Based Azomethine Ylides with α,β-Unsaturated Acyl Phosphonates for the Construction of Spiropyrrolidinyl-2,3′-oxindoles

A novel, one-pot 1,3-dipolar cycloaddition of 3-amimooxindole-based azomethine ylides with α,β-unsaturated acyl phosphonates and subsequent derivatization of the intermediates is described. Employing 4-(N,N-dimethylamino)pyridine (DMAP), an organic Brønsted base, as a robust catalyst leads to an architecturally diverse set of spiropyrrolidinyl-2,3′-oxindoles bearing four contiguous stereocenters and an ester or an amide at the γ-position of the pyrrolidine motif. The products are obtained in moderate to excellent yields and with good diastereoselectivities under mild conditions. The potential of this methodology is demonstrated through a gram-scale reaction and a further transformation of one of the products.