Phosphine- and Nitrogen-Containing Lewis Base Catalyzed Highly Regioselective and Geometric Selective Cyclization of Isatin Derived Electron-Deficient Alkenes with Ethyl 2,3-Butadienoate

An interesting phosphine-containing Lewis base catalyzed highly regioselective [3 + 2] cycloaddition and a novel nitrogen-containing Lewis base catalyzed highly geometric selective [4 + 2] cycloaddition of isatin derived α,β-unsaturated diesters with α-allenic ester have been disclosed to give the corresponding cyclic products in good to excellent yields under mild conditions. A plausible reaction mechanism has also been proposed on the basis of previous literature and our own investigation.