8-hydroxyquinoline groups

Studies of UV-vis spectra suggest that several bis-8-hydroxyquinoline-substi-tuted aza-crown ethers are potential chemosensors for Cu2+. As shown in Figure 8, addition of Cu2+ to an aqueous acetate-buffered solution of a tetraaza-15-crown-5 ligand functionalized with two 8-hydroxyquinoline groups (102) leads to a new peak at 258 nm which develops gradually.155 The other transition and posttransition metal ions, Co2+, Ni2+, Zn2+, Cd2+, Hg2+, Pb2+, and Ag+ (only Zn2+, Cd2+, and Pb2+... 

Polymer lOA (4.8 g) was reacted with 5-chloromethyl-8-hydroxyquinoline (3.0 g, 13 mmol) in HjO (10 ml) at 100°C for 4 hours. The usual work up yielded polymer 12A as yellow beads (5.82 g), containing per gram 1.07 mmol 8-hydroxyquinoline groups and 1.03 mmol NEtj, with 39% conversion of NH, groups to aminoquinoline groups. 

Casnati and co-workers have devised a calixarene crown ether (7.17) that shows a preference for potassium over sodium of 22,000.85 A macrocyclic polyether with attached 8-hydroxyquinoline groups (7.18) favors barium over other alkaline earth cations by a factor of more than 10 million.86 Compound (7.19) shows a preference of magnesium over calcium of 590.87 Compound (7.20) has the highest known binding constant for Ag(I), log K 19.6.88... 

Scheme 11 Binding modes of a pyridyl and b 8-hydroxyquinoline groups to the Ti02 surface...

Fixed dose combinations of hydroxyquinoline group of drugs with any other drug except for preparations meant for external use only. 

In the cases of 4-hydroxyquinoline and 4-methoxyquinoline the predominance of 6-nitration supports the evidence presented above that nitration in sulphuric acid proceeds via the cations. For both these compounds reaction via the neutral molecules would be expected to occur to a considerable extent at C(j) as a result of the directing properties of the hydroxyl and methoxyl groups. 

Partial rate factors for the nitration of 4-hydroxyquinoline and its derivatives are given in table 10.6. Comparison with the values for quinolinium (table 10.4) show that the introduction of a 4-hydroxy or a 4-methoxy group into the latter activates the 6-position by factors of 3-3 X 10 and 1-6 X 10 , respectively, and the 8-position by factors of 29-5 and 23, respectively. What has been said above makes the significance of partial rate factors which may be calculated for 4-hydroxy-cinnoline uncertain. 

In this work the results of reseai ch common sorbtion-X-Ray-fluorescence analysis of Pb(II), Cd(II), Zn(II) and Mo(VI) with preconcentration on complexing chemical silica gel modified with mercaptane groups and modified with 8-hydroxyquinoline were described. The conditions and limits of determination of the X-Ray-fluorescence method in the thin lawyers ai e discussion. 

In 1975, Weber and Vogtle showed that open-chained polyethers, 2,6-pyridine-dimethanol, and ortho-xylene derivatives terminated in an 8-quinolinyl group could form stable, 1 1, crystalline complexes with a variety of metal salts. The podands were prepared from 8-hydroxyquinoline and the corresponding dihalides. A typical example is shown in Eq. (7.10). 

The Pomeranz-Fritsch-Bobbitt cyclisation of activated amino-acetal 38 yielded the desired 4-hydroxyquinoline 39 in acceptable yield. The non-obvious regioselectivity of the cyclisation can be attributed to the overriding para-directing effect of alkoxy groups. ... 

The electronic spectrum of a compound arises from its 7r-electron system which, to a first approximation, is unaffected by substitution of an alkyl group for a hydrogen atom. Thus, comparison of the ultraviolet spectrum of a potentially tautomeric compound with the spectra of both alkylated forms often indicates which tautomer predominates. For example, Fig. 1 shows that 4-mercaptopyridine exists predominantly as pyrid-4-thione. In favorable cases, i.e., when the spectra of the two alkylated forms are very different and/or there are appreciable amounts of both forms present at equilibrium, the tautomeric constant can be evaluated. By using this method, it was shown, for example, that 6-hydroxyquinoline exists essentially as such in ethanol but that it is in equilibrium with about 1% of the zwitterion form in aqueous solution (Fig. 2). 

R = Ar) and cyclized tricyclic compound 240 (R = Ar) was obtained when 2-bromoacetophenones were reacted with 8-hydroxyquinolin-2(l//)-one under the above conditions. Presence of a 4-methoxy substituent shifted the equilibrium to the ring-opened product 241 (R = 4-MeOPh), while that of 4-nitro group gave only cyclized product 240 (R = N02). Similarly, mixtures of ring-opened and 2,3,6,7-tetrahydro-5//-pyrido[l,2,3- /e]-l,4-benzoxazin-5-one derivatives were formed in the reaction of 8-hydroxy-l,2,3,4-tetrahydroquinolin-2-one and halomethyl ketones (00HCA349). 

Hydroxyquinoline, having both a phenolic hydroxyl group and a basic nitrogen atom, is amphoteric in aqueous solution it is completely extracted from aqueous solution by chloroform at pH < 5 and pH > 9 the distribution coefficient of the neutral compound between chloroform and water is 720 at 18 °C. The usefulness of this sensitive reagent has been extended by the use of masking agents (cyanide, EDTA, citrate, tartrate, etc.) and by control of pH. 

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