Synthesis of Dispiro‐[Indoline‐3,1′‐Cyclopropane‐2′,3′′‐Indoline]‐2,2′′‐Diones via Thermal [2+1] Cycloaddition Between 3‐Alkylidene‐7‐Aza‐2‐Indolones and 3‐Diazo‐7‐Aza‐2‐Oxindoles

Abstract Diastereoselective synthesis of highly substituted dispiro‐[indoline‐3,1′‐cyclopropane‐2′,3′′‐indoline]‐2,2′′‐dione in excellent yield via an unusual catalyst‐free thermal [2+1]‐cycloaddition of E ‐3‐alkylidene‐7‐aza‐2‐indolones and 3‐diazo‐7‐aza‐2‐oxindoles under neat condition has been developed. The advantages of the approach include mild reaction conditions, substrate tolerance, broad scope, high yields, and selectivity of the reaction. A plausible reaction mechanism invoking a carbene intermediate and alkene [2+1]‐cyclization is proposed.