Wu Nai-Wei, Petsalakis Ioannis D, Theodorakopoulos Giannoula, Yu Yang, Rebek Julius
Center for Supramolecular and Catalytic Chemistry and Department of Chemistry, Shanghai University, 99 Shang-Da Road, Shanghai, 200444, China.
Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vassileos Constantinou Ave., Athens, 116 35, Greece.
Angew Chem Int Ed Engl. 2018 Nov 12;57(46):15091-15095. doi: 10.1002/anie.201808265. Epub 2018 Oct 24.
Described herein is the behavior of α,ω-dienes sequestered within cavitands in aqueous (D O) solution. Hydrophobic forces drive the dienes into the cavitands in conformations that best fill the available space. Shorter dienes (C9 and C10) bind in compressed conformations that tumble rapidly in the cavitands. Longer dienes induce capsule formation between cavitands with self-complementary hydrogen bonding sites, where the dienes exist in extended conformations. In cavitands unable to form capsules, longer dienes adopt folded structures. The wider open ends allow the synthesis of medium-sized cycloalkenes by ring-closing metathesis reactions with the Hoveyda-Grubbs-II catalyst. Yields of cycloheptene and cyclooctene were enhanced by the chaperones in water when compared with reactions of the free dienes in either aqueous media or chloroform, and even cyclononene could be prepared within the cavitand.
本文描述了在重水（D₂O）溶液中包结在穴状配体中的α,ω-二烯烃的行为。疏水作用力驱使二烯烃以最能填充可用空间的构象进入穴状配体。较短的二烯烃（C₉和C₁₀）以压缩构象结合，在穴状配体中快速翻转。较长的二烯烃在具有自互补氢键位点的穴状配体之间诱导形成胶囊，其中二烯烃以伸展构象存在。在无法形成胶囊的穴状配体中，较长的二烯烃采用折叠结构。较宽的开口端允许通过与霍维达-格鲁布斯-II催化剂进行关环复分解反应合成中等大小的环烯烃。与游离二烯烃在水性介质或氯仿中的反应相比，水中的分子伴侣提高了环庚烯和环辛烯的产率，甚至在穴状配体内也可以制备环壬烯。
