Allenic Esters from Cyclopropenones by Lewis Base Catalysis: Substrate Scope, the Asymmetric Variant from the Dynamic Kinetic Asymmetric Transformation, and Mechanistic Studies

The Lewis base catalyzed reactions of cyclopropenones with a variety of nucleophiles (alcohols, phenols, or water) were systematically investigated. We demonstrated that this kind of reaction could be used to synthesize allenic esters in moderate to excellent yields. Furthermore, more synthetically interesting axially chiral allenes in moderate to good yields and ee values were obtained in the corresponding asymmetric reaction in the presence of multifunctional chiral phosphine catalyst. The reaction mechanism was disclosed by using NMR tracing experiments, MS, and DFT calculations. Notably, the asymmetric reaction was proved to be a dynamic kinetic asymmetric transformation based on the control experiments, and the detailed mechanism of this transformation revealed by theoretical investigations.