Quinoline natural solid

The alumina or silica-alumina supports used in bifunctional catalysts have been shown to be acidic in nature. The acidic properties are readily demonstrated by the affinity of these solids for adsorption of basic compounds such as ammonia, trimethylamine, re-butylamine, pyridine, and quinoline (01, R5). Furthermore, adsorption of certain acid-base indicators such as butter yellow gives a coloration similar to that observed in acid media (B3, B4). With regard to the origin of the acidity, Tamele (Tl) has suggested in the case of silica-alumina that aluminum atoms replace silicon atoms in the surface of the silica structure, giving rise to surface sites of the form... 

An experimental study has shown that the addition of quinoline and phenanthrene to a n-hexadecane feedstock in MAT experiments leads to a loss in overall conversion. Characterisation of the coke from this feedstock, indicates that the initial coke formed is highly aliphatic in nature. Quinoline acts primarily as a catalyst poison but also favours coke formation. Solid state C NMR was used to characterise the coke formed from a heavy oil feedstock on demineralisation of the deactivated catalyst. The coke was now observed to be aromatic and highly condensed and it was possible to achieve this characterisation at realistic coke levels of ca. 1% without employment of large coke deposits as hitherto. 

The second major aspect of the surface chemistry of chromia-alumina that has to be considered is the acidic nature of its surface. The exact chemical nature of the acid sites of solid oxide catalysts such as alumina or silica-alumina has been a subject of considerable research and speculation for a number of years, yet despite these efforts a fully satisfactory chemical description of catalyst acidity has not been obtained. Nevertheless, in the case of chromia-alumina, there is good evidence for the existence of acid sites of one kind or another on the surface. Voltz and Weller (29), for example, studied the chemisorption of quinoline on chromia-alumina, with and without potassium promotion, and at the same time measured their titrable acidities in aqueous suspensions. Both methods indicated that chromia-alumina was acidic, and that the addition of potassium decreased the acidity. This observation was supported by the fact that the double bond isomerization of 1-pentene, normally an acid-catalyzed reaction, proceeded quite readily over pure chromia-alumina, but less readily over a chromia-alumina treated with potassium. 

The quinoline scaffold and derivatives occur in a large number of natural products and drug-like compounds. A method for microwave-assisted synthesis of 2-aminoquinolines has been described by Wilson et al. [62]. The process involves rapid microwave irradiation of secondary amines and aldehydes to form enamines, then addition of 2-azidobenzophenones with subsequent irradiation to produce the 2-aminoquinoline derivatives (Scheme 10.27). Purification of the products was accomplished in a streamlined manner by using solid-phase extraction techniques to produce the desired compounds in high yields and purity. Direct comparison of the reaction under thermal and microwave conditions, using identical stoichiometry and sealed reaction vessels, showed the latter resulted in improved yield. 

Recently has been discovered that an oxoiso orphine derivative with an amino group at the position 6 called Lakshminine (Figure 7) (6-amino-l-aza-5-methoxy-7//-dibenzo[rfe,/ ]quinolin-7-one ) has presented an interesting antiproliferative activity. This rare natural product has now been synthesized in order to have sufficient amounts for biological testing, its 4-amino isomer, their 6- and 4-nitro precursors, the intermediate 5-methoxy-7//-dibenzo[Je,/z]quinolin-7-one, and the unsubstituted skeleton were tested against normal human fibroblasts and three human solid tumor cell line s. Only the 4-nitro precursor showed marginal antiproliferative activity [34],... 

The coexistence of the NH-quinolin-4(lH)-one and 4-hydroxyquinoline isomers has been confirmed by spectrometric analysis. However, the exclusive NH-4-OXO nature of these alkaloids in solution phase (NMR) and solid state (IR and X-ray) has also been corroborated (213). For example, galipoline, isolated from Angostura trifoliate (Rutaceae) (Table VI), has the potential to exist in tautomeric equilibrium (Scheme 14), explaining a number of reports which have appeared showing the structure of galipoline (1,214), either as 2-(3, 4-dimethoxyphenylethyl)-4-hydroxyquinoline or as 2-(3,4-dimethoxyphenvlethvl)-quinolin-4(lH)-one (40). 

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