Double armed crown ethers

Double armed crown ethers" were prepared from corresponding di-azacrown ethers (Kryptofix 21, 22, and 23, Merck Japan). Typically, Kryptofix 22 (l,7,10,16-tetraoxa-4,13-diazacyclooctadecane) was condensed with 2-furoyl chloride, and the resultant diamide was reduced by diborane in THF. Recrystallization from CH Cl -hexane gave white crystals 4 Mp, 37-38°C. Elemental analysis Calcd. C 62.54, H 8.11,... 

Crown ethers 2 3 and 6 were similarly obtained. The structures of the prepared "double armed crown ethers" are shown in Figure 1. 

Transport Properties of "Double Armed Crown Ethers"... 

The ring size of the double armed crown ether was an essential factor determining transport properties. We examined furam-bearing crown ethers having 15- to 21-membered rings, As shown in Figure 4, they... 

Recently, l iriat ethers" and gther single armed crown ethers have extensively been investigated. They exhibited interesting cation binding and extracting profiles, based on their three-dimensional coordination geometry. Similar principles should be involved in the present "double armed crown ether" systems. 

As well known, 18-crown-6 type carriers transported NH cation but could not discriminate NH cation from K cation in the transport process. Furan-bearing double armed crown ether 4 also showed high transport efficiencies for both cations and seemed to be non-selective carrier in some sense. 

H.Tsukube, Double Armed Crown Ethers With Specific Cation Transport Ability , J.Chem.Soc.,Chem.Commun., 315 (1984). 

Liu, Y., Zhang, H. Y., Bai, X. P., Wada, T., and Inoue, Y. (2000) Molecular design of crown ethers. 21. Synthesis of novel double-armed benzo-15-crown-5 lariats and their complexation thermodynamics with light lanthanoid nitrates in acetonitrile, J. Org. Chem. 65, 7105-7109 see also Danil de Namor, A. F. D., Chahine, S., Jafou, O., and Baron, K. (2003) Solution thermodynamics of lanthanide-cryptand 222 complexation processes, J. Coord. Chem 56, 1245-1255 Israeli, Y., Bonal, C., Detellier, C., Morel, J. P., and Morel-Desrosiers, N. (2002) Complexation of the La(III) cation by p-sulfonatocalix[4]arene - A La-139 NMR study, Canad. J. Chem. 80, 163-168. 

Finally, a new type of crown ether, such as some double-armed diaza-crow ethers directly connected to various heteroaromatic rings, has been obtained by high-pressure. S yjAr reactions of heteroaromatic halides with the corresponding unsubstituted crown ethers. ... 

Liu. Y. Zhang, H. Y. Bai, X.-P. Wada, T. Inoue. Y. Molecular design of crown ethers. 21. Synthesis of novel double-armed benzo-15-crown-5 lariats and their complexation thermodynamics with light lanthanoid nitrates in acetonitrile. J. Org. Chem. 2000. 65. 7105-7109. 

Diaza[18]crown-6 (2.20) can also be readily functionalised with two side arms, instead of just one as in 2.21, to form double lariat ethers termed bibracchial lariat ethers (BiBLEs), such as 2.24. This modification results in the possibility of the side arms covering both faces of the macrocycle (Figure 2.6(a)). A particularly striking example is the complexation of sodium in a BiBLE that contains two thymine groups as the side arms (Figure 2.6(b)). 

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