Synthesis of Binol-based diphosphinites bearing chiral phospholane units and their application in asymmetric catalysis

New diphosphinite ligands based on atropoisomeric diol backbones and (R,R)-2,5-dimethylphospholane moieties have been prepared and fully characterised. For each ligand structure, both diastereomers have been synthesised. These ligands are available through a straightforward procedure in good yields. The solid state structures of two diastereomeric ligands are reported. These ligands have been applied to Rh-catalysed asymmetric hydrogenations and hydroformylations of CC bonds as well as in Ir-catalysed asymmetric hydrogenations of CN bonds. Turnover frequencies in the range of 10,000 h−1 and enantioselectivities of up to 98% ee have been achieved. The different chirality elements within the ligands led to marked cooperative effect in catalysis. Interestingly, there is no general privileged diastereomeric structure but rather a matched diastereomer for each application.

Figure optionsDownload as PowerPoint slide

(Ra)-2,2′-Bis((2R,5R)-2,5-dimethylphospholan-1-yloxy)-1,1′-binaphthylC32H36O2P2[α]D22=+186.8 (c 0.73, CH2Cl2)Source of chirality: the precursorAbsolute configuration: (Ra)-(2R,5R)

(Ra)-2,2′-Bis((2R,5R)-2,5-dimethylphospholan-1-yloxy)-5,5′,6,6′,7,7′,8,8′-octahydro-1,1′-binaphthylC32H44O2P2[α]D22=+121.3 (c 1.03, CH2Cl2)Source of chirality: the precursorAbsolute configuration: (Ra)-(2R,5R)

(Sa)-2,2′-Bis((2R,5R)-2,5-dimethylphospholan-1-yloxy)-1,1′-binaphthylC32H36O2P2[α]D22=+14.6 (c 0.77, CH2Cl2)Source of chirality: the precursorAbsolute configuration: (Sa)-(2R,5R)

(Sa)-2,2′-Bis((2R,5R)-2,5-dimethylphospholan-1-yloxy)-5,5′,6,6′,7,7′,8,8′-octahydro-1,1′-binaphthylC32H44O2P2[α]D22=+36.9 (c 1.07, CH2Cl2)Source of chirality: the precursorAbsolute configuration: (Sa)-(2R,5R)