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.