Phosphine-catalyzed [3 + 2] annulation of 2-aminoacrylates with allenoates and mechanistic studies

Abstract

A convenient and efficient strategy for the synthesis of 3-pyrrolines containing an amino quaternary stereogenic center via phosphine-catalyzed formal [3 + 2] annulation of 2-aminoacrylates with allenoates is disclosed. A wide range of substrates underwent this reaction smoothly, affording a series of 3-pyrrolines in good to excellent yields, and it could be extended to a gram-scale reaction. The kinetic profiles and the calculated methyl anion affinity (MAA) values were employed to explain the reactivities of different allenoates used in the reaction, which provides deep understanding for the catalytic mechanism of this type of reaction.