Determination of absolute configuration using vibrational circular dichroism spectroscopy: the chiral sulfoxide 1-thiochroman S-oxide |
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Affiliation: | 1. Science and Technology on Reactor Fuel and Materials Laboratory, Nuclear Power Institute of China, Chengdu, China;2. The College of Nuclear Technology and Automation Engineering, Chengdu University of Technology, Chengdu, China |
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Abstract: | We have determined the absolute configuration of the chiral sulfoxide 1-thiochroman S-oxide 1 using vibrational circular dichroism (VCD) spectroscopy. The VCD spectrum of a CCl4 solution of 1 was analyzed using density functional theory (DFT), which predicts three stable conformations of 1, separated by <1 kcal/mol. The VCD spectrum predicted using the DFT/GIAO methodology for the equilibrium mixture of the three conformations of (S)-1 is in excellent agreement with the experimental spectrum of (+)-1. The absolute configuration of 1 is therefore (R)-(−)/(S)-(+). (+)-1 and (−)-1 of high enantiomeric excess (e.e.) were synthesized in high yields via asymmetric oxidation of 1-thiochroman 2 using Ti(iso-PrO)4/(R,R)-1,2-diphenylethane-1,2-diol/H2O/tert-butyl hydroperoxide and Ti(iso-PrO)4/l-diethyl tartrate/H2O/cumene hydroperoxide, respectively. |
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