Stereochemistry of Seven-membered Heterocycles: XLIV. Spatial Structure of 4-R-3,5-Dioxabicyclo[5.1.0]octanes
作者:V. Yu. Fedorenko、R. N. Baryshnikov、B. I. Khairutdinov、R. M. Vafina、Yu. G. Shtyrlin、V. V. Klochkov、E. N. Klimovitskii
DOI:10.1007/s11178-005-0160-8
日期:2005.2
4-R-3,5-Dioxabicyclo[5.1.0]octanes were prepared in good yields by reduction of the corresponding 8,8-dichloro derivatives in a system Li-t-BuOH. According to the data of dynamic 1H and 13CNMR spectroscopy involving experiments in the NOESY mode the formal (R = H) at −93°C in (CD3)2CO exists in nearly equally occupied chair forms with endo- and exo-oriented three-membered ring. The like structure were found in the diastereomeric 4-Me(t-Bu)-analogs. The characteristic feature of 13C NMR spectra consists in considerable difference in the chemical shifts of the C8 atoms (Δδ∼16–17 ppm). The data on epimerization of diastereomers and calculations along AM1 procedure suggest for formal a three-component equilibrium including a twist-form.
通过在 Li-t-BuOH 体系中还原相应的 8,8-二氯衍生物,制备了 4-R-3,5-二氧杂环[5.1.0]辛烷,并获得了良好的产率。根据动态 1H 和 13CNMR 光谱在 NOESY 模式下的实验数据,(CD3)2CO 中的形式(R = H)在-93°C 时几乎以内向和外向三元环的均等占位椅型存在。在非对映的 4-Me(t-Bu)-类似物中也发现了类似的结构。13C NMR 光谱的特点是 C8 原子的化学位移差异很大(Δδ∼16-17 ppm)。非对映异构体的表聚化数据和按照 AM1 程序进行的计算表明,正式的三组分平衡包括一种扭转形式。