Bis(cycloocta‐1,5‐diene)nickel‐Catalyzed Carbon Dioxide Fixation for the Stereoselective Synthesis of 3‐Alkylidene‐2‐indolinones

A bis(cycloocta‐1,5‐diene)nickel‐catalyzed highly regio‐ and (E)‐stereoselective hydrocarboxylation of 2‐alkynylanilines under very mild conditions has been developed to afford (E)‐[2‐(o‐aminophenyl)]acrylic acids, which could easily be converted to (E)‐3‐alkylidene‐2‐indolinones with important potential bioactivity. The stereoselective syntheses of two biologically active molecules, (E)‐3‐benzylidene‐2‐indolinone (chemo‐preventive potential in inducing NQO1 activity) and (E)‐3‐(3‐methylbutylidene)‐2‐indolinone (a natural product isolated from Cimicifuga foetida with cytotoxic activity against HL‐60 cells) are presented as examples.