Chromatographic resolution, solution and crystal phase conformations, and absolute configuration of tert-butyl(dimethylamino)phenylphosphine-borane complex.
The enantiomers of tert-butyl(dimethylamino)phenylphosphine-borane complex 2 have been separated by HPLC using cellulose tris-p-methylbenzoate as chiral stationary phase. The borane protection could be removed without racemization and the P-configuration of the free aminophosphine 1 has shown to be stable in solution. Infrared (IR) and vibrational circular dichroism (VCD) spectra have been measured in CD2Cl2 solution for both enantiomers. B3LYP/6-31+G(d) DFT calculations allowed a prediction that complex (S)-2 exists as three conformers in equilibrium and computed population-weighted IR and VCD spectra. Predicted and experimental IR and VCD spectra compared very well and indicate that enantiomer (+)-2 has the S absolute configuration. This assignment has been confirmed by an X-ray diffraction study on a single crystal of (+)-2. The crystal structure of enantiomerically pure 2 appears to be very close to the most stable computed conformer which proved to be predominant in solution.
Naubron
Jean-Valère
JV
UMR 6180 CNRS: "Chirotechnologies: Catalyse et Biocatalyse", Université Paul Cézanne, EGIM, Avenue Escadrille Normandie-Niémen, 13397 Marseille Cedex 20, France.
Giordano
Laurent
L
Fotiadu
Frédéric
F
Bürgi
Thomas
T
Vanthuyne
Nicolas
N
Roussel
Christian
C
Buono
Gérard
G