An Improved Catalytic System, Pd(PPh3)4/PhCOOH Combined Catalyst, for the Allylation of Carbon Pronucleophiles with Allenes

ABSTRACT The reaction of allenes with active methynes and methylenes proceeded smoothly in the presence of Pd(PPh 3 ) 4 /PhCOOH combined catalyst to give the corresponding monoallylated products with E-stereoselectivity in good to high yields. This result is in marked contrast to the previous finding that the reaction of allenes with active methynes, in the presence of Pd 2 (dba) 3 ·CHCl 3 /dppb catalyst, affords the allylation products in lower yield with lower stereoselectivities.