Regioselective routes to disubstituted dibenzo crown ethers and their complexations
作者:Harry W. Gibson、Hong Wang、Klaus Bonrad、Jason W. Jones、Carla Slebodnick、Lev N. Zackharov、Arnold L. Rheingold、Bradley Habenicht、Peter Lobue、Amy E. Ratliff
DOI:10.1039/b503072m
日期:——
Two isomers of bis(carbomethoxybenzo)-24-crown-8 (cis-BCMB24C8, 1, and trans-BCMB24C8, 2) were synthesized regiospecifically with acceptable to excellent yields. Cyclization in the presence of a template reagent, KPF6, led to an essentially quantitative yield of the potassium complex of the crown ether 1; the isolated cyclization yield of pure 1 was a remarkable 89%! The methods not only avoid the very difficult separation of the isomers, but also greatly shorten the synthesis time by eliminating syringe pump usage during cyclization. The complexations of the isomeric BCMB24C8 with dibenzylammonium hexafluorophosphate (10) were studied by NMR; association constants (Ka) for 1 and 2 with the dibenzylammonium cation are 190 and 312 M−1, respectively. The X-ray crystal structures of crown ether 2 and the complexes 1·KPF6, 2·KPF6 and pseudorotaxane 2·10 were determined.
两种双(羧甲氧基苯)24冠8(顺式BCMB24C8,1和反式BCMB24C8,2)的异构体被特异性合成,产率良好到优秀。在模板剂KPF6的存在下环化,冠醚1的钾复合物产率几乎定量;纯品1的分离环化产率高达惊人的89%!这些方法不仅避免了异构体非常难以分离的问题,还通过消除环化过程中使用注射泵而大大缩短了合成时间。通过NMR研究了异构体BCMB24C8与二苄基铵六氟磷酸盐(10)的配位作用;顺式1和反式2与二苄基铵阳离子的结合常数(Ka)分别为190和312 M−1。测定了冠醚2及其复合物1·KPF6、2·KPF6和假轮烷2·10的X射线晶体结构。