4-nitrobenzo-15-crown

We have noted above that benzocrowns may be nitrated quite readily. This approach was used in the formation of a photoresponsive bis-crown (see Sect. 3.8) wherein the nitrobenzo crowns reductively dimerize to the corresponding azobenzene. Kikukawa, Nagira and Matsuda have utilized 4-nitrobenzo-15-crown-5 in a somewhat different way during the synthesis of 4 -vinylbenzo-l 5-crown-5Nitration is effected using nitric acid in a mbcture of chloroform and acetic acid. 

Hydrogenation reduces the nitro group to amino which is then diazotized using sodium nitrite and tetrafluoroboric acid. The diazotized crown was not isolated but the aq. solution was treated directly with sodium acetate and bis(dibenzylideneacetone)-pal-ladium(O) in acetonitrile solution. Ethylene was then introduced to the autoclave and the solution was allowed to stir for 2 days. 4 -Vinylbenzo-15-crown-5 was isolated (30% from 4 -nitrobenzo-15-crown-5) as a colorless solid (mp 43.5—44.2°) °. The synthesis is illustrated in Eq. (3.16). 

Nakamura, Takagi and Ueno have also utilized 4 -nitrobenzo-l 5-crown-5 as a starting material Their goal was the formation of a colored crown which could be utilized in transport studies. They have prepared 4 -picrylaminobenzo-l 5-crown-5 for this purpose in the following way. 4 -Nitrobenzo-l 5-crown-5 was hydrogenated and then picryl chloride was added. Nucleophilic aromatic substitution apparently ensued (deep red color) and the product was th n isolated by standard techniques as a yellow solid (mp 155°, max 395 nm) in 72% yield as shown in Eq. (3.17). 

Another interesting variation on the linkage holding together two benzocrowns was reported by Shinkai and coworkers In their case, the benzo groups on the crowns were also part of a photolabile azobenzene system. The azo-linked bis-crown was prepared as follows (see Eq. 3.34). 4 -Nitrobenzo-l 5-crown-5 was reductively dimerized... 

In the presence of the reactive initiator phenyl p-nitrobenzoate 2198 phenoxy-trimethylsilane 13d is ehminated in the CsF/18-crown-6 catalyzed polymerization of silylated phenyl p-N-(n-octyl)aminobenzoate 2199 in THF to form the polymer 2200 [12] (Scheme 14.4). 

The kinetics of the esterification of potassium p-nitrobenzoate by benzyl bromide in dichloromethane-water catalysed by dicyclohexyl-18-crown-6 ([20] + [21]) has been studied by Wong (1978). At low catalyst concentrations (e.g. 5.0 x 10 3 M) he found that 22% of the product was formed by the SN1 and 78% by the SN2 mechanism. Higher catalyst concentrations increased the salt concentration in the organic phase, and the contribution of the SN1 mechanism becomes negligibly small. 

All other chemicals employed were of the highest grade available. 5-Nitro-l,10-phenanthroline, 5-amino-l,10-phenanthroline [6] and benzo[15-crown-5], 15-nitrobenzo[15-crown-5], 15-aminobenzo[15-crown-5] were prepared according to the published methods [7, 8],... 

Nitrobenzo-15-crown-5 [6083569-0] M 313.3, m 84-85 , 93-95 . Recrystd from EtOH, MeOH... 

Where the lanthanide ionic radius and the macrocyclic cavity are incompatible, though in hydrous conditions the crown ether is likely to be displaced by water ligands, the crown may still be present in the structure of the crystal as a hydrogen-bonded adduct. This behaviour is seen in [Gd(N03)3(H20)3]-(18-crown-6).445 This type of compound is quite well known in the case of s block metals also, e.g. [Mg(H20)6]Cl2 (12-crown-4)454 and, a more subtle case, [Ca(nitrobenzoate)2(benzo-15-crown-5)]-3H20(benzo-15-crown-5)455 in which an apparent 2 1 complex has only half its crown ligand coordinated to Ca2+. 

We have studied the interactions of the crown ether 4-nitrobenzo-15-crown-5 at the water/dichloroethane interface [78] (Figure 1.11). The variation of the SHG signal from this crown ether as a function of potential across the interface depends dramatically on the presence or absence of sodium ions. The neutral crown ether behaves quite differently from the charges cation-crown ether complex. At the hepatane/water interface, cation binding has been studied using dye-labelled crowns [79]. We are currently investigating the behaviour of other crown ethers at the air/water and solvent/water interfaces. 

C14H160 isobutyl 2-naphthyl ether 2173-57-1 25.00 1.0130 2 27545 C14H19N07 nitrobenzo-15-crown-5 60835-69-0 25.00 1.2574 2... 

C15H18N208 4-isocyanato-5 -nitrobenzo-15-crown-5 83935-64-2 25.00 1.3527 2 28723 C15H23N304S N-((1-ethyl-2-pyrrolidinyl)methyl)-5-sulfamo 15676-16-1 25.00 1.2116 2... 

Hg(II) Crown 18C6, 4 -nitrobenzo[15-crown-5], calix oligomer deriv., bis-calix[4]arene ester derivative [178-186] ... 

Wong,K. H., and A. P. W. Wai, Solid-Liquid Phase Transfer Kinetics of / -Nitrobenzoate Esterification Catalyzed by Crown Ethers ... 

When the omega phase is formed, the overall reaction rate can be described by pseudo-first-order kinetics with respect to the organic reactant. While the reaction follows pseudo-zero-order kinetics as the substitution reaction is conducted in the presence of crown ether and in the absence of water, it is independent of the benzyl halide concentration. Crown ether directly dissociates the cation of the reacting salt. A reaction mechanism was proposed for the esterification reaction of solid potassium 4-nitrobenzoate and benzyl bromide by using crown ether [197], The overall reaction is... 

In the elimination of HOTs from exo-2-norbornyl tosylate using the sodium salt of 2-cyclohexylcyclohexanol in triglyme at 80 °C, syn-exo elimination is at least 100 times faster than anti elimination. If 18-crown-6 is added, the rate ratio falls to ca. 15 1, indicating that the presence of the sodium cation is important in the complex transition state of the syn process. Pyrolysis of urethanes of borneol and isoborneol has been re-examined and found to give mixtures including a-pinene, tricyclene, camphene, and alcohols. Pyrolysis of nitrobenzoates gives no alcohols but camph-ene, tricyclene, and bornene. ... 

---