K2CO3-Promoted Formal [3+3]-Cycloaddition of N-Unsubstituted Isatin N,N'-Cyclic Azomethine Imine 1,3-Dipoles with Knoevenagel Adducts.

The synthesis of dicyclic spiropyridazine oxoindole derivatives by using [3+3]-cycloaddition of N-unsubstituted isatin N,N'-cyclic azomethine imine 1,3-dipoles was reported. The products bearing two consecutive stereocenters, including spiroquaternary stereocenters in one ring structure, can be effectively obtained in moderate to excellent yields (20-93%) and low to moderate diastereoselectivities (1:9-10:1 dr). The synthesized compounds (>35 examples) were characterized by single-crystal XRD, FTIR, NMR, and mass spectral analysis.

DABCO-Catalyzed Mono-/Diallylation of N-Unsubstituted Isatin N,N'-Cyclic Azomethine Imine 1,3-Dipoles with Morita-Baylis-Hillman Carbonates.

Allylation of N-unsubstituted isatin N,N'-cyclic azomethine imines with Morita-Baylis-Hillman carbonates in the presence of 1-10 mol% DABCO in DCM at room temperature, rapidly gave N-allylated and N, ß-diallylated isatin N,N'-cyclic azomethine imine 1,3-dipoles in moderate to high yields. The reaction features mild reaction conditions, easily practical operation, and short reaction times in most cases. Furthermore, the alkylated products were transformed into novel bicyclic spiropyrrolidine oxoindole derivatives through the [3+2] or [3+3]-cycloaddition with maleimides or Knoevenagel adducts.