Lewis-Base-Catalyzed Domino Reaction of Morita-Baylis-Hillman Carbonates of Isatins with Enolizable Cyclic Carbonyl Compounds: Stereoselective Access to Spirooxindole-Pyrans

The present paper reports an efficient, organocatalytic, environmentally friendly and stereoselective [3+3] one-pot allylic alkylation/oxa-Michael reaction by involving a wide range of Morita-Baylis-Hillman (MBH) carbonates of isatins and several pharmacologically attractive enolizable C-H activated cyclic carbonyl compounds such as 1,3-binucleophiles, namely pyrazolones, isoxazolones, 4-hydroxyxoumarins, 4-hydroxy-6-methyl-alpha-pyrone, lawsone and dimedone in a biomass-derived 2-MeTHF as green solvent catalyzed by DABCO as a solid Lewis-base catalyst. This protocol delivers a unique class of medicinally promising spirooxindole-fused-dihydropyran scaffolds.