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

A series of N-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_N2‘−S_N2‘ mechanism.