Synthesis of new N-substituted chiral phosphine–phosphoramidite ligands and their application in asymmetric hydrogenations and allylic alkylations

Phosphine–phosphoramidite ligands containing a 2,4-pentanediyl backbone, BINOL moieties, and Me, Bn or Ph substituent on the nitrogen were synthesized and fully characterized. The electronic effect of the N-substituents was examined by 31P NMR of their corresponding seleno-phosphate-amide and phosphine–selenide derivatives. The new ligands together with their earlier reported derivatives were tested in the palladium catalyzed asymmetric allylic alkylation of rac-(E)-1,3-diphenylallyl acetate. Remarkably high activity (up to 1780 h−1 turnover frequency) and first order kinetics were observed by facilitating nucleophile formation. The substituent at the nitrogen and the configuration of chiral moieties had a high impact on the enantioselectivity. The new ligands were also tested in the rhodium-catalyzed asymmetric hydrogenation of methyl (Z)-α-acetamidocinnammate, dimethyl itaconate (up to 99.9% ee’s) and methyl 2-acetamidoacrylate (up to 99.5% ee).

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(11bS)-N-((2S,4S)-4-(Diphenylphosphino)pentan-2-yl)-N-benzyl-{dinaphtho[2,1-d:1′,2′-f][1,3,2]dioxaphosphepin-2-yl}-4-amineC44H39NO2P2[α]D20 = +129.2 (c 1, CH2Cl2)Source of chirality: (S)-H0-BINOL, (2R,4R)-pentane-2,4-diol and stereoselective synthesis

(11bS)-N-((2S,4S)-4-(Diphenylphosphino)pentan-2-yl)-N-phenyl-{dinaphtho[2,1-d:1′,2′-f][1,3,2]dioxaphosphepin-2-yl}-4-amineC43H37NO2P2[α]D20 = +89.4 (c 1, CH2Cl2)Source of chirality: (S)-H0-BINOL, (2R,4R)-pentane-2,4-diol and stereoselective synthesis

(11bS)-N-((2S,4S)-4-(Diphenylphosphino)pentan-2-yl)-N-methyl-{dinaphtho[2,1-d:1′,2′-f][1,3,2]dioxaphosphepin-2-yl}-4-amineC38H35NO2P2[α]D20 = +244.2 (c 1, CH2Cl2)Source of chirality: (S)-H0-BINOL, (2R,4R)-pentane-2,4-diol and stereoselective synthesis