The conformation of trans-2,11-dithia-4e,5,6,7e,8,9-hexahydro[3.3]paracyclophanes (5, tDTHHPCP) was investigated by using H-1 NMR analysis under variable-temperature condition. Based on the dynamic H-1 NMR behavior along with a structure obtained from simulation using the MM2 method, it has been deduced that 5 occurs preferentially in conformer 5a in CD2Cl2 solution, which the two sulfur atoms are situated as the chair form and cyclohexano unit as a distorted boat form. The energy barrier (Delta G double dagger) for the inversion of the bridge (-CH2SCH2-) has been estimated to be 11.6 kcal mol(-1) (600 MHz, Tc = -30 degrees C). The proton chemical shifts are assigned for the individual hydrogen according to the spectra obtained at -70 degrees C.
JOURNAL OF THE CHINESE CHEMICAL SOCIETY, 59(3):373-377.