Phosphine-Catalyzed Allylic Substitution of Morita−Baylis−Hillman Acetates:  Synthesis of N-Protected β-Aminophosphonic Acid Esters

A series of <i>N</i>-protected β-amino phosphonic acid esters have been prepared by phosphine-catalyzed allylic substitution of 2-(diethylphosphonyl)-substituted allylic acetates employing 4,5-dichlorophthalimide as nucleophilic partner. These organocatalytic allylic substitutions exhibit exceptionally high levels of regiospecificity by virtue of a tandem S<sub>N</sub>2‘−S<sub>N</sub>2‘ mechanism.