Highly Functionalized 4‐Oxothiazolidin‐5‐ylidene Synthesis Involving C─C Coupled Aromatization with Dual C─N and C─S Bond Forming Cyclization Through Aminolysis

An efficient protocol for the construction of highly functionalized 4‐oxothiazolidin‐5‐ylidene derivatives using a K 2 CO 3 ‐catalyzed reaction between 3,5,6,7‐tetrahydro‐1 H ‐indole‐2,4‐diones and isothiocyanates, followed by AcOH‐promoted cyclization with dialkyl but‐2‐ynedioates, is described. This efficient three‐component reaction approach produced desired compounds in 74%–89% yields under mild conditions. The resultant compounds have bioactive scaffolds of 4‐oxothiazolidin‐5‐ylidene and hexahydro‐3 H ‐indol‐3‐ylidene, indicating potential for therapeutic use. Mechanistic studies revealed 4‐oxothiazolidin‐5‐ylidene as a key intermediate. Crystal structure of a representative compound ethyl ( Z )‐2‐(2‐(( Z )‐1‐(3‐bromophenyl)‐6,6‐dimethyl‐2,4‐dioxo‐1,2,4,5,6,7‐hexa hydro‐3 H ‐indol‐3‐ylidene)‐3‐(4‐methoxyphenyl)‐4‐oxothia zolidin‐5‐ylidene)acetate was confirmed via X‐ray diffraction analysis.