Induction of reversal chirality by C-2-symmetric diamide linked-diphosphine ligands in catalytic asymmetric allylations

Bridging parts X between two amide skeletons of C-2-symmetric diphosphine l igands 1 were varied using various kinds of diacyl chlorides. The ligand Ic derived from phthaloyl chloride, which was remarkably effective in the asy mmetric induction on palladium-catalyzed asymmetric allylic substitutions o f 2-cyclohexenyl pivalate or acetate, exhibited a moderate level of enantio selectivity, 72% ee, in the transformations of 1,3-diphenyl-2-propenyl piva late. The newly developed ligands 1g-i having one carbon spacers X demonstr ated 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 us ing 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 chiralit y model. (C) 2000 Elsevier Science Ltd. All rights reserved.