Induction of reversal chirality by C2-symmetric diamide linked-diphosphine ligands in catalytic asymmetric allylations

Abstract

Bridging parts X between two amide skeletons of C 2-symmetric diphosphine ligands 1 were varied using various kinds of diacyl chlorides. The ligand 1c derived from phthaloyl chloride, which was remarkably effective in the asymmetric induction on palladium-catalyzed asymmetric allylic substitutions of 2-cyclohexenyl pivalate or acetate, exhibited a moderate level of enantioselectivity, 72% ee, in the transformations of 1,3-diphenyl-2-propenyl pivalate. The newly developed ligands 1g– i having one carbon spacers X demonstrated higher degrees of enantiomeric excess up to 93% ee. Interestingly, the present reactions catalyzed by Pd– 1c– e, g– j complexes afforded the product 4 with the opposite absolute configuration S compared with the reactions using VALAP, which has the same chiral source as that of 1. The ligands 1a, b, f exhibited the induction of R configuration although the yields were very low. The production of S- 4 was discussed on the basis of the Pr/ Mr chirality model.