Regioselective routes to disubstituted dibenzo crown ethers and their complexations.
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, KPF(6), led to an essentially quantitative yield of the potassium complex of the crown ether 1; the isolated cyclization yield of pure 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 and the complexes 1.KPF(6), 2.KPF(6) and pseudorotaxane 2.10 were determined.
Gibson
Harry W
HW
Chemistry Department, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0212, USA. hwgibson@vt.edu
Wang
Hong
H
Bonrad
Klaus
K
Jones
Jason W
JW
Slebodnick
Carla
C
Zackharov
Lev N
LN
Rheingold
Arnold L
AL
Habenicht
Bradley
B
Lobue
Peter
P
Ratliff
Amy E
AE