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.