Dibenzo-27-crown-9 derivatives

Low-symmetry crown ethers, possessing (3m + )-crown- z scaffolds, show a less pronounced binding ability than symmetrical crown ethers, but display much higher selectivities for specific cations . For instance, polymer membrane thallium(l)-selective electrodes based on dibenzo-crown ether derivatives 67 have been developed <1996CCR171>, because of the environmental and biological implications associated with the poisoning of Tl+ ions. 

Crown ether-functionalized polyphenylenes are a class of electroactive polymers obtained by electropolymerization (anodic coupling) of (di)benzo- or (bi)naphthalene-crown ethers <1998CCR1211, 1998PAC1253>. Tricyclic triphenyl-ene derivatives, such as 78, can be electrogenerated from benzo-15-crown-5 <1989NJC131> and benzo-18-crown-6 <1992JEC399>. Similarly, the anodic oxidation of dibenzo-crown ethers has produced poly(dibenzo-crown ethers), best represented by 79, where triphenylene moieties are presumably two-dimensionally linked via polyether bridges. 

Hdgberg and Cram (1975) and Biernat and Luboch (1984) prepared some dibenzodiaza-, triaza-, and tetraaza-crowns from a bis-tosylanilide derivative prepared from o-nitrophenol (method V-7). This procedure allows the synthesis of dibenzo-crowns containing from two to four nitrogen atoms de-... 

In addition to PPy and PTh derivatives, numerous reports have focused on the synthesis and the properties of electroactive polymer films electrogenerated from the oxidation of crown ether-substituted benzenes [273-286] and naphthalenes [17, 287-293]. Among them, poly(dibenzo-crown ether)s and, especially, poly(dibenzo-18-crown-6) have been the most extensively studied, owing to their remarkable structural, electrochemical, and complexing properties [278-280]. Furthermore, their affinity for a large variety of cations, including heavy metal and precious metal cations, was greatly improved when they were previously undoped [281-286]. 

M -Dialkyldiazacrown ethers and their precursors fcis(alkylamino) derivatives of tri- and tetraethylene glycols were prepared <96CCCC622>. New hydroxy-bearing dibenzo-azocrown ethers have been conveniently prepared utilizing l,3-Ws(2-formylphenoxy)-2-propanol and a diamine, followed by reduction of the intermediate diimine <96P1197>. Fluorescent photoinduced electron transfer sensor 5 with monoaza-18-crown-6 and guanidinium receptor units demonstrated a fluorescence with T -aminobutyric acid in a mixed... 

Barboiu, M., Supuran, C.T., Luca, C., Popescu, G. and Barboiu, C. (1996) Functionalized derivatives of benzocrown-ethers. Part I. Ionophores containing amino and pyridinium groups derived from benzo-15-crown-5, benzo-18-crown-6 and dibenzo-18-crown-6. Liebigs Annalen der Chemie, 959-963. 

Fixing the location of the counterion midway between two identical electrophores has been achieved in the radical anion of the dibenzo[ 18] crown-6 derivative [46] (Mazur et al, 1980). When its radical anion exists as the ion pair with Na + or K+, the intramolecular electron transfer becomes detectable on the esr timescale. The activation energy determined for the electron transfer (1.4 kcal mol-1) clearly demonstrates that in this case a significant contribution to the activation barrier from ion pairing can be negated. 

Shchori et al. (1971, 1973) have pointed to the remarkable similarity ( a = 12.6 + 0.7 kcal mol-1) of the activation energies for decomplexation of dibenzo-18-crown-6 [11] and substituted derivatives (Table 20). They too were of the opinion that the activation energy for decomplexation reflects the energy required for a conformational rearrangement. The fact that different crown ethers give different a values can also be explained by this model. 

The behaviour of the dibenzo-18-crown-6 derivative is similar, yet the highest attainable rate is only one eighth of that observed with dicyclohexyl-18-crown-6, which points to an important difference in reactivity between crown ether-separated ion pairs. Compared to tetrabutylammonium phenoxide, the dicyclohexyl-18-crown-6/K+ phenoxide was 2.6 times less reactive. The addition of 0.05 M dicyclohexyl-18-crown-6 to dioxan resulted in the alkylation rate constant becoming the same as that observed in pure tetraglyme. 

Many crown compounds have been investigated as specific ionophores for Li+, for example, dibenzo-18-crown-6 (42) or dicyclohexano-18-crown-6 (43) in conjunction with the cobalticarborane anion (41). The sensitivity of such combinations is higher for K+ than for Li+ (55 vs. 14 and 51 vs. 27 mV per M concentration decade, respectively) . Other examples are the 16-crown-4 derivatives 44a-d, for which in the best case the LiSE shows a higher than 600-fold selectivity for Li+ vs. Na+ compound 44a with the THE units in cw-configuration has excellent selectivity for Li+ vs. Na+. K+, NH, Mg + and Ca , and the components of blood serum do not interfere with the Li+ determination 5,5-dibenzyl-14-crown-4 (45) also shows good selectivity . Placing bulky substituents... 

TTie discovery (70) that [Pt(bipy)(NH3)2] is encapsulated in both the solid and solution states by the constitutionally symmetrical dibenzo-30-crown-10 derivative 6 (p 210) has led (71) to the realization that this easily accessible... 

In the latter case, a dibenzo-30-crown-10 derivative of unspecified constitution was also isolated. 

During the past two decades, a relatively few macrocyclic polyethers have played central roles in numerous research programs. Examples are 18-crown-6, dibenzo-18-crown-6, and aza-15-crown-5. 4,13-D1aza-18-crown-6 and its derivatives are compounds of considerable current interest despite the parent s high price and limited availability. 4,13-Diaza-18-crown-6 is a key compound in the study of two-armed macrocycles since it may readily be alkylated or acylated to afford a variety of symmetrical, N,N -disubstituted derivatives. 

Using a typical poly (vinyl chloride) (PVC)-based membrane with different ionophores - Zn-bis(2,4,4-trimethylpen-tyl) dithiophosphinic acid complex [450], protoporphyrin IX dimethyl ester [451], porphyrin derivative [452] and hemato-porphyrin IX [453], tetra(2-aminophenyl) porphyrin [454], cryptands [455, 456], 12-crown-4 [457], benzo-substituted macro-cyclic diamide [458], 5,6,14,15-dibenzo-l, 4-dioxa-8,l 2, diazacyclopentadecane-5,14-diene [459], and (A-[(ethyl-l-pyrrolidinyl-2 -methyl) ] methoxy-2-sulfamoyl-5 -benza-mide [460] - the sensors for zinc ions were prepared and investigated. The armed macrocycle, 5,7,7,12,14,14-hexamethyl-1,4,8,11 -tetraazacyclo tetradeca-4,11 -diene dihydrogen perchlorate was used for the preparation of polystyrene-based Zn(II)-sensitive electrode [461]. 

A variety of benzyl fluorides 9 were directly prepared in one-step from the corresponding benzyl alcohols 8 by using a combination of methanesulfonyl fluoride and cesium fluoride in the presence of dibenzo-18-crown-6.167 The mesylates formed in situ are thus easily converted to the fluoro derivatives 9. 

Scheme 54 Dibenzo[30] crown-10 derivative 106 carrying four Percec-type dendrons...

Scheme 55 Liquid crystalline derivative 107 of dibenzo[18]crown-6 stabilized by internal hydrogen bonds...

Akopova synthesized enamine ketone derivative 107 of dibenzo[18]crown-6 (Scheme 55) which exhibits columnar mesomorphism [8]. An interesting feature of compound 107 is the hydrogen-bond mediated stabilization within the side group. 

---