Chiral 4-(diphenylphosphanyl)-1-(dialkylamino)butane ligands - Synthesis, applications in asymmetric alkylation and theoretical study

Various 4-(diphenylphosphanyl)-1-(dialkylamino)butane ligands were prepared from commercial (2S,3S)-2,3-O-isopropylidene-d-threitol. These ligands, as sociated with Pd-2(dba)(3), gave enantioselectivities of up to 75% in the a lkylation of racemic 1,3-diphenylprop-2-enyl acetate with dimethyl malonate anion. A theoretical study shows the important role played by two factors in the alkylation reaction: steric control, leading to the formation of a u nique diastereoisomer of the pi-allylpalladium complex, and orbital control , which orients the attack of the nucleophile trans to the phosphorus atom.