Absolute configuration of tert-butyl-1-(2-methylnaphthyl)phosphine oxide.
The enantiomers of tert-butyl-1-(2-methylnaphthyl)phosphine oxide 1 have been separated using a homemade HPLC column and an analytical gradient system. Vibrational absorption and circular dichroism spectra for both enantiomers have been measured in CD2Cl2 and CH2Cl2 solutions in the 2000-900 cm(-1) region. The fully relaxed potential energy surface of (S)-tert-butyl-1-(2-methylnaphthyl)phosphine oxide, obtained using the B3LYP functional with a 6-31G basis set, indicated two stable conformers with their populations in a approximately 2:1 ratio. The vibrational absorption and VCD spectra are predicted for these two conformers using the B3LYP functional with a 6-31G basis set. The comparison of predicted and experimental spectra indicated that (+)-tert-butyl-1-(2-methylnaphthyl)phosphine oxide is in the (S)-configuration. This assignment is supported by the ab initio prediction of positive optical rotation for the most stable conformer with an (S)-configuration and the nonequivalence sense of the tert-butyl group chemical shift observed in the 1H NMR spectrum of this enantiomer measured in the presence of (+)-(S)-mandelic acid as a chiral solvating agent.
Wang
Feng
F
Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, USA.
Wang
Yan
Y
Polavarapu
Prasad L
PL
Li
Tingyu
T
Drabowicz
Józef
J
Pietrusiewicz
K Michal
KM
Zygo
Krystyna
K
D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D009682:Magnetic Resonance Spectroscopy; D008333:Mandelic Acids / Q000737:chemistry; D008968:Molecular Conformation; D015394:Molecular Structure; D009281:Naphthalenes / Q000138:chemical synthesis / Q000737:chemistry*; D009943:Organophosphorus Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D013237:Stereoisomerism
D008333:Mandelic Acids; D009281:Naphthalenes; D009943:Organophosphorus Compounds; C468510:tert-butyl-1-(2-methylnaphthyl)phosphine oxide; C037938:mandelic acid