BINOL-derived diphosphoramidites bearing unsymmetrical 1,2-diamine link and their application in asymmetric catalysis

New P,P-bidentate diastereomeric diphosphoramidite chiral ligands with mixed stereogenic elements and a C1 backbone symmetry have been prepared from (Sa)- and (Ra)-1,1′-binaphthyl-2,2′-diol (BINOL) and (S)-N-benzyl-1-(pyrrolidin-2-yl)methanamine and are fully characterized. The use of these ligands provides up to 84% ee in the Pd-catalyzed asymmetric allylic substitution of (E)-1,3-diphenylallyl acetate and up to 95% ee in the Rh-catalyzed asymmetric hydrogenation of α-dehydrocarboxylic acid esters. The results indicate that the catalytic performance is highly affected by the axial chirality of the binaphthyl moieties of the ligand and the nature of the solvent.

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(Sa,Sa)-N-Benzyl-N-(((2S)-1-(dinaphtho[2,1-d:1′,2′-f][1,3,2]dioxaphosphepin-4-yl)pyrrolidin-2-yl)methyl)dinaphtho[2,1-d:1′,2′-f][1,3,2]dioxaphosphepin-4-amineC52H40N2O4P2Ee = 100%[α]D20=+168.7 (c 1.0, CHCl3)Source of chirality: (S)-(+)-pyroglutamic acid(Sa)-1,1′-binaphthyl-2,2′-diolAbsolute configuration: (Sa,Sa,2S)

(Ra,Ra)-N-Benzyl-N-(((2S)-1-(dinaphtho[2,1-d:1′,2′-f][1,3,2]dioxaphosphepin-4-yl)pyrrolidin-2-yl)methyl)dinaphtho[2,1-d:1′,2′-f][1,3,2]dioxaphosphepin-4-amineC52H40N2O4P2Ee = 100%[α]D20=+122.3 (c 1.0, CHCl3)Source of chirality: (S)-(+)-pyroglutamic acid(Ra)-1,1′-binaphthyl-2,2′-diolAbsolute configuration: (Ra,Ra,2S)