Comparison of dynamic HPLC and dynamic NMR in the study of conformational stereodynamics: Case of the enantiomers of a hindered secondary phosphine oxide

Static and dynamic stereochemistry of HP(O)(BuAr)-Ar-t (Ar = 2-methyl-1-nap hthyl) has been studied by a combination of variable-temperature NMR (H-1 a nd P-13), HPLC, and CD measurements as well as by MM calculations. Two uneq ually populated stereolabile isomers for each configurational enantiomer ha ve been detected and their anticlinal and synclinal structures assigned. Al l the four species have been physically separated and identified on a cryog enic HPLC enantioselective column at -83 degrees C. The interconversion bar rier measured by dynamic NMR yields essentially the same value as that meas ured by dynamic HPLC (14.75 and 14.95 kcal mol(-1), respectively).