Syntheses of Aromatic Bridged Cryptophanes and their Complexing Abilities with Alkyl Ammonium Cations

Abstract

Several aromatic bridged cryptophanes were successfully synthesized. p-Xylene bridged cryptophane Anti-3 was prepared by the direct trimerization of ci,ci'-bis[4-hydroxyme thyl-2-methoxyphenoxy]-p-xylene. The synthesis of o-xylene bridged cryptophane Anti4 was carried out by the direct trimerization and/or the stepwise method from vanillyl alcohol. The 0-[4,5-bis-(methoxycarbonyl)]xylene bridged cryptophanes Anti-15a and Syn-15b were also prepared by the stepwise method from vanillyl alcohol. Anti-3 was capable of complexing with almost all the quaternary alkylammonium cations among the primary, secondary, tertiary and quaternary ammonium cations, and selectively prefered to complex with the NEt,Me+ cation as a guest. From the complexation of the o-xylene bridged cryptophanes Anti-8, and the analogs Anti15a and Syn-15b with the NMe,+ cation, the cryptophanes Anti-8 and Syn-15b were confirmed to complex with the guest cation, however, Anti-15a was not confirmed to be included.

Cryptophanes and Their Complexes—Present and Future

“…The same experiments were performed with xylylene-bridged cryptophanes (see Chart ) . The upfield shifts of the proton resonances of the Et 3 MeN + , Et 4 N + , EtMe 3 N + , and Me 4 N + ions were characteristic of their encapsulation by cryptophane 13 .…”

“…The same experiments were performed with xylylenebridged cryptophanes (see Chart 5). 33 The upfield shifts of the proton resonances of the Et 3 MeN + , Et 4 N + , EtMe 3 N + , and Me 4 N + ions were characteristic of their encapsulation by cryptophane 13. Due to competition with the solvent (CD 2 Cl 2 /CD 3 OD; 9:1), only apparent stability constants were estimated, and these showed a higher selectivity for Et 3 MeN + (Figure 25).…”

“…Similarly, from the bis-vanillyl alcohol 14 , cryptophane 15 with o -xylylene bridges was obtained with comparable yields (Scheme ). The reactions run in formic acid at room temperature appeared to be stereospecific, as the anti isomers were exclusively recovered . A new type of cryptophane with diethyleneoxy bridges was prepared from the precursor 16 heated at 55−60 °C in formic acid (Scheme ).…”

“…Again using the template method, the same authors reported the synthesis of cryptophanes possessing xylylene bridges. , The reaction of CTV 50 with benzyl alcohol derivatives 60 and 61 afforded compounds 62 and 63 , respectively, in good yields. The anti/syn cryptophanes 13/64 and 65 / 66 with D 3 / C 3 h symmetry were obtained in moderate yields by treating compounds 62 and 63 , respectively, in formic acid at room temperature (Scheme ).…”

Anion binding, aryl-extended cyclotriguaiacylenes and an aryl-bridged cryptophane that provides snapshots of a molecular gating mechanism

“…Other arene-bridged cryptophanes, e.g. those possessing para-or ortho-xylyl bridges, are known to form kinetically stable complexes with small alkyl ammonium cations at low temperatures (51). Specifically, the anti diastereomer of the six-carbon, p-xylyl-bridged cryptophane (Scheme 1, R 1 ¼ R 2 ¼ OCH 3 ), forms a more stable [DG8(210 K) ¼ 2 2.9 -kcal/mol] complex with NEt 3 Me þ than with smaller or larger cations.…”