在三丁基膦作为催化剂的存在下,由庞大的酸酐将由24元冠醚和在末端带有羟基的仲铵盐组成的拟轮烷定量酰化,从而以高收率得到相应的轮烷。无需色谱分离即可轻松实现大规模合成。在过量的三烷基胺存在下,用过量的亲电子试剂将所得轮烷中的铵基团定量酰化。通过该顺序的双酰化方案制备了各种N-官能化的轮烷。1个轮烷的1 H NMR光谱和X射线晶体学分析表明,冠状醚组分通过强的氢键键合相互作用而被捕获在铵型轮烷中的铵基上。铵基周围的构象通过氢键相互作用而固定。同时,酰胺型轮烷的构象由冠醚中的亚甲基与车轴组件的苯环之间的弱CH /π相互作用确定。铵型轮烷的N-酰化可用于制备功能化的轮烷和弱的基于组分间相互作用的轮烷。
Redox Behavior of Ferrocene-Containing Rotaxane: Transposition of the Rotaxane Wheel by Redox Reaction of a Ferrocene Moiety Tethered at the End of the Axle
rotaxane with a ferrocene moiety at the axle terminus was prepared. The redox potential of the ferrocene moiety decreased by ca. 80 mV when the rotaxane had a crown ether wheel capable of moving on the axle. Thus, the stabilization of the oxidized state of the ferrocene moiety is assumed to accompany the transposition of the wheel component on the axle toward the ferrocene moiety. [reaction--see text]
Direct Preparation of Rotaxane from Aminoalcohol: Selective<i>O</i>-Acylation of Aminoalcohol in the Presence of Trifluoromethanesulfonic Acid and Crown Ether
Selective O-acylation of aminoalcohols by a bulky acid anhydride in the presence of trifluoromethanesulfonic acid and dibenzo-24-crown-8 afforded [2]rotaxane in high yields. An acid halide could be used as an acylating reagent in the presence of silver trifluoromethanesulfonate.
Rotaxanes possessing a cinnamyl ester group at the axle terminal were prepared. The terminal end-cap was modified with a bulky malonate ester in excellent yield by the Tsuji-Trost allylation reaction, which was carried out in the presence of a palladium catalyst.
Thermoresponsive Shuttling of Rotaxane Containing Trichloroacetate Ion
A thermoresponsive rotaxane shuttling system was developed with a trichloroacetate counteranion of an ammonium/crown ether-type rotaxane. Chemoselective thermal decomposition of the ammonium trichloroacetate moiety on the rotaxane yielded the corresponding nonionic rotaxane accompanied by a positional change of the crown ether on the axle. The rotaxane skeleton facilitated effective dissociation of the acid, markedly lowering the thermal decomposition temperature.
Sequential <i>O</i>- and <i>N</i>-Acylation Protocol for High-Yield Preparation and Modification of Rotaxanes: Synthesis, Functionalization, Structure, and Intercomponent Interaction of Rotaxanes
catalyst to afford the corresponding rotaxane in high yield. Large-scale synthesis without chromatographic separation was easily achieved. The ammonium group in the resulting rotaxane was quantitatively acylated with excess electrophile in the presence of excess trialkylamine. Various N-functionalized rotaxanes were prepared by this sequential double-acylation protocol. 1H NMR spectra and X-ray crystallographic
在三丁基膦作为催化剂的存在下,由庞大的酸酐将由24元冠醚和在末端带有羟基的仲铵盐组成的拟轮烷定量酰化,从而以高收率得到相应的轮烷。无需色谱分离即可轻松实现大规模合成。在过量的三烷基胺存在下,用过量的亲电子试剂将所得轮烷中的铵基团定量酰化。通过该顺序的双酰化方案制备了各种N-官能化的轮烷。1个轮烷的1 H NMR光谱和X射线晶体学分析表明,冠状醚组分通过强的氢键键合相互作用而被捕获在铵型轮烷中的铵基上。铵基周围的构象通过氢键相互作用而固定。同时,酰胺型轮烷的构象由冠醚中的亚甲基与车轴组件的苯环之间的弱CH /π相互作用确定。铵型轮烷的N-酰化可用于制备功能化的轮烷和弱的基于组分间相互作用的轮烷。