Environmental Friendly Synthesis of Novel Isatin Ketal and Isatin Schiff Base Derivatives Using Michael Addition Reaction under Solvent‐Free Conditions

An efficient and simple procedure for the synthesis of novel isatin derivatives is described. Michael addition of aniline Schiff bases of isatin or p‐toluidine Schiff bases of isatin to fumaric esters affords the Michael adduct compounds in good to high yields in the presence of K₂CO₃ and tetrabutylammonium bromide (TBAB) under solvent‐free conditions. Repeating of this reaction about spiro1,3‐dioxolane‐2,3′‐indol]‐2′(1′H)‐one, as a Michael donor, in the presence of 1,4‐diazabicyclo2.2.2]octane (DABCO) gives Michael adducts in remarkable yields under the same conditions.