Design of a new axially chiral molecule by conformational fixation: 2,6-dithiaspiro[3.3]heptane 2,6-dioxide and its heavier analogues

作者：Naruse Yuji^*; Hasegawa Yousuke; Araki Motoya

来源：Tetrahedron: Asymmetry , 2013, 24(13-14): 781-784.

DOI：10.1016/j.tetasy.2013.05.020

We have designed a new axially chiral bis(sulfoxide) molecule with conformational rigidity: 2,6-dithiaspiro[3.3]heptane 2,6-dioxide 2a. This molecule has axial asymmetry due to two puckered thietane ring systems. The lone pairs on the sulfur show a strong s-character, which was expected to result in a high barrier to racemization, that is, inversion at the sulfur. We confirmed this prediction by calculations and experimentation. The lone pairs of the sulfur in 2a are sp(1.00) and the enthalpy of activation (Delta H-double dagger) for inversion is 47.5 kcal/mol (B3LYP/6-31G(d)). The H-1 NMR spectra of 2a showed two doublets and two doubled doublet peaks, which resulted from the rigidity of the four-membered ring frameworks without flipping. We separated the enantiomers of 2a by HPLC with a chiral stationary phase column to observe a set of complementary peaks. We also calculated the diselena- and ditellura congeners and confirmed that they also show axial chirality.

• 出版日期2013-7-31