Flexible molecules with defined shape. Part 3. Conformational analysis of bis(tetrahydropyran-2-yl)methanes
作者:Reinhard W. Hoffmann、B. Colin Kahrs、Jan Schiffer、J�rg Fleischhauer
DOI:10.1039/p29960002407
日期:——
(R,R)-Bis(tetrahydropyran-2-yl)methane 4 along with its racemate have been synthesized. MM3 calculations suggest that the conformer 4a should be populated to ca. 85% in the conformer equilibrium. Analysis of the 1H NMR coupling constants show that one conformer predominates by about 9 : 1. That this is the conformer 4a is shown by various NMR techniques, as well as by comparison of calculated with measured CD spectroscopic data. The study is extended to the methyl-substituted bis(tetrahydropyranyl)methanes 21 and 23 which show, as predicted from MM3 calculations, essentially mono-conformational behaviour.
(R,R)-双(四氢吡喃-2-基)甲烷4及其外消旋体已经合成。 MM3 计算表明构象异构体 4a 应填充到大约。 85%处于构象异构体平衡。 1H NMR耦合常数的分析表明,一种构象异构体占主导地位,比例约为9:1。通过各种NMR技术以及通过计算的CD光谱数据与测量的CD光谱数据的比较,表明这是构象异构体4a。该研究扩展到甲基取代的双(四氢吡喃基)甲烷 21 和 23,正如 MM3 计算所预测的那样,它们基本上显示出单构象行为。