Sequential Multicomponent Strategy for the Diastereoselective Synthesis of Densely Functionalized Spirooxindole-Fused Thiazolidines

We developed two
Ugi-type three-component reactions of spirooxindole-fused
3-thiazolines, isocyanides, and either carboxylic acids or trimethylsilyl
azide, to give highly functionalized spirooxindole-fused thiazolidines.
Two diverse libraries were generated using practical and robust procedures
affording the products in typically good yields. The obtained thiazolidines
proved to be suitable substrates for further transformations. Notably,
both the Ugi-Joullié and the azido-Ugi reactions resulted highly
diastereoselective, affording predominantly the trans-configured products,
as confirmed by X-ray crystallographic analysis.