Regio‐ and Stereoselective Synthesis of 3‐Pyrazolylidene‐2‐oxindole Compounds by Nucleophilic Vinylic Substitution of ( E )‐3‐(Nitromethylene)indolin‐2‐one

A highly regio‐ and stereoselective synthesis of 3‐alkylidene‐2‐oxindoles has been described through a nucleophilic vinylic substitution (S N V) of ( E )‐3‐(nitromethylene)indolin‐2‐one using pyrazol‐3‐ones as nucleophiles and Et 3 N as a base. The reaction affords selectively the Z ‐isomer when pyrazol‐3‐ones without substituents at the 4 position are used. While the reaction is E ‐selective with 4‐substituted pyrazolones. The stereoselectivity (up to >20:1) and the yields (up to 98%) are very high under mild reaction conditions.