1-(1-Naphthyl)-2-naphthol → (1,1'-Biphenyl)-2,2'-diol

Beteiligte Stoffe

Reaktionsschritte

As shown in Table 1, the reaction proceeded smoothly at room temperature in the presence of [Ir(cod)Cl]2 (1 mol %) and phosphoramidite ligand 1 above (2 mol %, L/Ir=1) to give after 10 h branched product 3 in 84% isolated yield with excellent regioselectivity (3/4/5=98/1/1) and 95% enantiomeric excess (entry 1). Reaction at 50° C. for 4 h gave 89% of product 3 with 94% ee (entry 2). Reactions catalyzed by complexes of the diastereomeric form of phosphoramidite ligand L1 with opposite relative configuration of the binaphthol and amine unit were slow, even at 50° C., and formed the opposite enantiomer in 66% yield and 75% ee (entry 3). Complexes of binaphthol-derived ligands with achiral and smaller substituents at nitrogen (e.g., phosphoramidite ligand L3) produced lower ee's than did those of phosphoramidite ligand L1 (entry 4). Phosphoramidite ligand L2 with a biphenol unit gave product with a lower, though substantial enantioselectivity of 87% (entry 5).

Herkunft & Nachweise