Quinoline methyl-substituted

Most of the reactions with quinolines and degassed Raney nickels have been carried out at the atmospheric boiling point (above 230 C), a condition which is known to favor the formation of by-products. With quinoline and 4-methylquinoline (lepidine), however, the yields of the 2,2 -biquinolines were increased three to four times by heating in vacuo at 150° C, and it seems probable that other quinolines will behave similarly. Table II also shows that the yields of 2,2 -biquino-lines obtained under comparable conditions vary with the position of the methyl group in a fashion reminiscent of the trends observed with the pyridines (Table I). This similarity extends to the behavior of the two 2-methyl substituted quinolines studied, which undergo loss of the 2-methyl group to some extent and form traces of 2,2 -biquinolines. 

In general, symmetrical oxo-squaraines having the same end-groups are synthesized by reacting squaric acid with two equivalents of quatemized indolenine, 2-methyl-substituted benzothiazole, benzoselenazole, pyridine, quinoline [39, 45, 46] (Fig. 4) in a mixture of 1-butanol - toluene or 1-butanol - benzene with azeotropic removal of water in presence [39, 45] or absence [47] of quinoline as a catalyst. Other reported solvent systems include 1-butanol - pyridine [48], 1-propanol - chlorobenzene, or a mixture of acetic acid with pyridine and acetic anhydride [49]. Low CH-acidic, heterocyclic compounds such as quatemized aryl-azoles and benzoxazole do not react, and the corresponding oxo-squaraines cannot be obtained using this method [23, 50]. 

The proposed pathways for methyl-substituted quinolines differ from those shown in Fig. 23, even for the same culture, and most particularly, the fact that no C—N bond cleavage has been observed in most of the strains. A limited number of methylquinolines can be hydroxylated due to the inhibiting and blocking effect of the methyl group, particularly at position 2. So, neither P. aeruginosa QP nor P. putida QP could metabolize 2-methylquinoline however, a new strain of Pseudomonas (MQP) isolated by Grant and Al-Najjar [328] was reported to be able to transform 2-methylquinoline, yielding... 

Yu et al. synthesized two methyl-substituted Alq3, named tris(2,3-dimethyl-8-hydroxy-quinoline) aluminum complex (Alm23q3, 237) (Scheme 3.72) [264]. This compound emits blue color with an emission peak centered at 470 nm and FWHM of 90 nm. OLEDs with a structure of ITO/TPD/Alm23q3/Mg Ag emit blue light and the luminous efficiency is 0.62 lm/W with a maximum luminance of 5400 cd/m2 at 19 V. 

Reduction of quinolines in acid solution at a lead cathode or by dissolving zinc leads to attack on the heterocyclic ring with the formation of 4,4-coupled products, together with the tetrahydroquinoline [82,83]. In the case of 2- and 4-methyl substituted quinolines, dimeric products are obtained in 10 90 % yields. In these processes, dimerization of the one-electron addition product is in competition with further reduction to give the 1,4-dihydroquinoline, The latter is an enamine and it... 

A reinvestigation of the experiments on the UV irradiation of l-acetyl-l,2-dihydroquinoline-2-carbonitriles (Reissert compounds) 561 unequivocally demonstrated that the rearrangement via the diradical intermediate 562 gave 4//-3,l-benzoxazines 563 and 565 rather than the benzazete derivatives described earlier. The yields and the type of products were strongly influenced by the substituent R at position 4 while irradiation of the unsubstituted quinoline 561 (R=H) gave 3,1-benzoxazine 563 in nearly quantitative yield, the amount of the corresponding methyl-substituted analog 565 that could be isolated was considerable lower, due to its irreversible isomerization via 562 to the stable cycloprop[/ ]indole derivative 564 (Scheme 107) <199811(49)121 >. 

Benzisothiazole is a very pale yellow oil, b.p. 242°/748 mm, 70°/0.5 mm, with a characteristic odor similar to that of quinoline.96, 97,105 The methyl-substituted derivatives so far examined are also liquids, but other substituted 2,1-benzisothiazoles are generally colorless crystalline solids. A full list of 2,1-benzisothiazoles is given in the tables at the end of this chapter. The nitrogen atom in 2,1-benzisothiazoles is weakly basic, and these compounds dissolve in concentrated hydrochloric acid, but are reprecipitated on dilution. 

The importance of steric strain arising from benzo fusion in pyridines was first estimated by Packer and Wong (58JA905) in quaternization of methyl-substituted quinolines and isoquinolines. They used the strained homo-morph concept of Brown (53JA1) to approximate strains existing in naphthalene compounds of similar geometry (e.g., 1-methylquinoline and 1-methylnaphthalene) (Scheme 8). 

Shaw and Stapp studied the selectivity of various transition metal catalysts in the hydrogenation of methyl-substituted quinolines in hexadecane mostly at 100-160°C and an initial hydrogen pressure of 5.17 MPa (at room temperature).15 As seen from the results shown in Table 12.4, with 2-methylquinoline the selectivity to 1,2,3,4-... 

TABLE 12.4 Selectivities of Transition Metals in the Hydrogenation of Methyl-Substituted Quinolines to Tetrahydroquinolinesa i... 

TABLE 12.5 Selective Hydrogenation of Methyl-Substituted Quinolines to 1,2,3,4-Tetrahydroquinolines in the Presence of Sulfur Compounds or Carbon Monoxide ... 

Long-chain halides undergo this reaction at 100°, no C-dialkylated products being formed. In alkylations with aryl-substituted alkyl halides, Ar(CH,) X, n= 1 to 3, yields are improved by performing the reaction rapidly in liquid ammonia (56-9S>%). Also, quinoline methylated in the 2-or 4-position reacts in the same way. A methyl group in the 3-position of pyridine or quinoline is unreactive. 

Pyridine and quinoline derivatives substituted with methyl groups in the a or y position also form carbanions readily. In the presence of a strong base, such as phenyl lithium, one of the aliphatic hydrogen atoms of a-picoline is replaced and the useful synthetic intermediate (XIX) is formed.11 Although organo-lithium compounds show many of the prop-... 

Oxazolo[3,2-a]quinolinium, 2-methyl-13C NMR, 6, 652 (67JHC66) lH,3H-Oxazolo[4,3-c][l,4]thiazine-6-carboxylic acid 7-oxide, 8,8a-dihydro-3,3-dimethyl-, methyl ester X-ray, 6, 647 (74JCS(P2)1132) lH,3H,5/f-Oxazolo[3,4-a]quinoline, 1-substituted X-ray, 6, 646 <79JCS(P1)1013>... 

Nagao, M., Wakabayashi, K., Kasai, H., Nishimura, S., and Sugimura, T. (1981). Effect of methyl substitution on mutagenicities of 2-amino-3-methylimidazo[4,5-f]quinoline, isolated from broiled sardine. Carcinogenesis, 2 1147-1149. 

SCHEME 13.31 Diastereoselective hydrogenation of methyl-substituted quinolines 96. 

Parvatkar et al. [47] developed a facile one-pot synthetic methodology of substituted linear and angular indoloquinoline derivatives 19 by the reaction of indole-3-carboxaldehyde and substituted anilines in the presence of iodine as a catalyst (Scheme 10.13). Some indolo[2,3-Z)]quinolines were tested against human hepatocellular carcinoma HepG2 and human breast carcinoma MCF-7 cells. In an antiproliferative assay against human hepatocellular carcinoma HepG2 and human breast carcinoma MCF-7 cells, methyl-substituted 6//-indolo[2,3-(>]quinoline was found to be most active. 

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