[Pd(Ar-BIAN)(alkene)]-Catalyzed Highly Chemo-, Regio-, and Stereoselective Semihydrogenation of 1,2-Allenyl Phosphonates and Related Compounds

Often elusive, trisubstituted (Z)‐1‐alkenyl phosphonates can be prepared by the semihydrogenation of allenyl phosphonates in the presence of Pd complex 1. This reaction, which occurs in high yield with high chemo‐, regio‐, and stereoselectivity, can be extended to related functionalized allenes and the corresponding Z alkene products (see scheme). R1=H, alkyl, aryl, benzyl; R2,R3=H, alkyl; FG=P(O)(OR)2, P(O)Ph2, SO2Ph, COOEt.