Hydroquinoline

Hydropyridinyl radicals ESR, 2, 145 Hydroquinoline synthesis, 1, 441 Hydroquinones synthesis, 1, 417 of-Hydroxy acids dehydrogenation by flavins, 1, 253... 

Lithium aluminum hydride reduction of pyridinium salts is very similar to sodium horohydride reduction and gives similar products, but the ratio of 1,2- and 1,4-dihydro- or tetrahydropyridines differs considerably (5). Isoquinolinium salts are reduced hy sodium borohydride or lithium aluminum hydride in a manner identical to pyridinium salts (5). Quino-linium salts are reduced by sodium borohydride to give primarily tetra-hydroquinolines (72) as shown by the conversion of 33 to 34 and 35. When lithium aluminum hydride is used, the product is usually the dihydroquinoline (73) as shown in the conversion of 36 to 37 and 38. 

Pyrolytic ring closure of 3-o-aminophenyl-2,4-dioxo-l,2,3,4-tetra-hydroquinoline (172) gave a mixture of the a- and y-oxodihydro-carbolines 171 and 173. ... 

Similar pyrimidine-to-pyridine conversions were also reported for purine and 8-azapurine with C-H active acetonitriles, ethyl acetoacetate, acetylacetone with dimedone 8-azapurine is converted into triazolotetra-hydroquinoline (Scheme 15) (73JCS(P1)1620, S(Pl)1625, S(P1)1794). 

Chloro-1 -ethyl-6-fluoro-4-0x0-1,4-di-hydroquinoline-3<arboxylic acid Norfloxacin... 

Cd(8-hydroquinoline-5-sulfonate)+2e, NaOH, Cd(C104)2, 8-hydroquinoline-5-sulfonic acid ... 

Researchers at Lilly have prepared a series of alkylamine H3 antagonists. Examples include the amide (57), which has a of 1.05 nM and the tetra-hydroisoquinoline (58), which has a A) of 0.37 nM [132]. Both compounds are inactive at the Hi, H2, and H4 receptors. This same group also disclosed a series of azepines, represented by (59) (H3 A j = 0.85 nM) and (60) [133]. Compound (60) is reported to have 100% bioavailability and a 12.4 h half-life in rat. Related dihydroindoles such as (61) (A j = 0.5nM) and tetra-hydroquinolines were also shown to be H3 antagonists [134]. 

Phenolic antioxidants in rubber extracts were determined indirectly photometrically after reaction with Fe(III) salts which form a red Fe(II)-dipyridyl compound. The method was applicable to Vulkanox BKF and Vulkanox KB [52]. Similarly, aromatic amines (Vulkanox PBN, 4020, DDA, 4010 NA) were determined photometrically after coupling with Echtrotsalz GG (4-nitrobenzdiazonium fluoroborate). For qualitative analysis of vulcanisation accelerators in extracts of rubbers and elastomers colour reactions with dithio-carbamates (for Vulkacit P, ZP, L, LDA, LDB, WL), thiuram derivatives (for Vulkacit I), zinc 2-mercaptobenzthiazol (for Vulkacit ZM, DM, F, AZ, CZ, MOZ, DZ) and hexamethylene tetramine (for Vulkacit H30), were mentioned as well as PC and TLC analyses (according to DIN 53622) followed by IR identification [52]. 8-Hydroquinoline extraction of interference ions and alizarin-La3+ complexation were utilised for the spectrophotometric determination of fluorine in silica used as an antistatic agent in PE [74], Also Polygard (trisnonylphenylphosphite) in styrene-butadienes has been determined by colorimetric methods [75,76], Most procedures are fairly dated for more detailed descriptions see references [25,42,44],... 

Hydroprocessing, in petroleum refining, 18 654-657 Hydropulping, 10 535 Hydropyrolysis, coal liquefaction, 6 854 Hydroquinolines, 21 198-199 Hydroquinone (HQ) from benzene, 3 620 as a black-and-white chemical reducing agent, 19 205-206 in bleaching preparations, 7 847 clathrates, 14 160 dye releaser, 19 291-292 inclusion compounds in, 14 172, 174 intermediate used in oxidation hair dyes, 7 858t... 

Pyridine (and quinoline) which in so many respects are aromatic and comparable to benzene, lose this character completely on hydrogenation to piperidine (and hydroquinoline), which are entirely of the same nature as secondary aliphatic amines. The completely hydrogenated heterocyclic bases undergo degradation reactions which have become important particularly in the investigation of the constitution of alkaloids. A. W. Hofmann s method of opening rings by means of exhaustive methylation may be illustrated with piperidine. By thermal decomposition of the quaternary ammonium base a C—N-link-age is broken and at the same time water is eliminated. 

Leeson PD, Carling RW, Moore KW, Moseley AM, Smith JD, Stevenson G, Chan T, Baker FAC, Grimwood S, Kemp JA, Marshall GR, Hoogsteen K (1992) 4-Amido-2-carboxytetra-hydroquinolines, structure-activity relationships for antagonism at the glycine site of the NMD A receptor. J Med Chem 35 1954-1968... 

Disubstitutedpyridines. A typical reaction is the synthesis of 5,6,7,8-telra-hydroquinoline (equation I). If the thermolysis is carried out in the absence of oxygen, the yield of the pyridine is 3%. 

These compounds usually show other reactions typical of their aliphatic analogues. 1,2,3,4-Tetra-hydroquinoline (532 Z = NH) is thus an /V-alkylaniline chroman (532, X = O) is an alkyl aryl ether. 

Intramolecular [4 + 2] cycloaddition reactions of enamides have provided a route to hydroindole and hydroquinoline ring systems (80JA3294,5274). In this work, the diene portion was initially masked as a 2-substituted 2,5-dihydrothiophene 1,1-dioxide. Thus, reaction of the acid chloride (312) with 3,4,5,6-tetrahydropyridine (311) afforded the masked enamido diene (313), which was converted to the enamido diene (314) upon brief refluxing in xylene. Thermolysis of (314) afforded the hydrolulolidine (315) in 45-55% yield. Additionally, (313) could be transformed to (315) directly by passage of a 1% solution in toluene through a vertical tube (600 °C oven temperature) (Scheme 67). The method was used to prepare a known precursor to aspidospermine. 

Phenyl- 2/f-azirine 3-Phenyl-2 H-azirine 2,3,4,5,6,7,8 a-Octa-hydroquinoline ... 

The ethyl ester of l-cyclopropyl-7-(2,6-dimethyl-4-pyridyl)-5,6,8-trifluoro-4-oxo-1,4-di-hydroquinoline-3-carboxylic acid26 and of the closely related (7>)-10-(2,6-dimethyl-4-pyridyl)-8,9-difluoro-3-methyl-7-oxo-2.3-dihydro-7//-pyrido[1,2,3-tfe]-l,4-bcnzoxazine-6-carboxylic acid 427 can be thiolated in tetrahydrofuran at low temperature, using the strong base sodium hydride. 

Vinylpyridines add to TV-alkyl- or phenyl-substituted maleimides to give unexpected 1 2 and 1 3 adducts. From the reaction of 2-vinylpyridine 99 with N-alkylmaleimides the 1 2 addition products 154, which are tetra-hydroquinoline derivatives, could be isolated in the presence of polymerization inhibitors. Furthermore, 1 3 adducts 155 are formed, representing an unusual type of cycloaddition involving the pyridine ring. On the other hand, 4-vinylpyridine 156 combines with 3 moles of dienophilic N-alkylmaleimides in the presence of polymerization inhibitors to afford the spiro compounds 157 (73HCA440). 

Intra- and intermolecular aza-Diels-Alder reactions of o-azaxylylenes give rise to hydroquinoline (Scheme 86) <1999AG(E)1928>. 

Examples of the versatility of photochemical hetero Diels-Alder photocycloadditions have also been reported. Thus, the 2,4,6-triphenylpyrylium terafluoroborate (TPT) photocatalyzed reaction of arylimines with N-vinyl-2-pyrrolidinone and N-vinylcarbazole represents a convenient approach for the preparation of tetra-hydroquinoline derivatives under mild conditions (Scheme 9.31) [52],... 

In a report describing new syntheses of substituted quinolines, furo[2,3-g]quinolines (34) and (35) were prepared in high yield from the same 7-allylquinolinol (Scheme 1) <83JOC774>. Reductive desulfonylation of these tricyclics with LAH gave 2-methylfuro[2,3-g]quinoline (36) and the unsubstituted parent heterocycle (37), respectively. The latter could also be prepared in good yield by a simultaneous desulfurization-aromatization route from 5-(phenylsulfonyl)-6-oxo-5,6,7,8-tetra-hydroquinoline. The versatility of this second route is demonstrated by the synthesis of the isomeric furo[3,2- ]quinoline (38) shown in Scheme 2. 

Quinoline was electrolyzed by Ahrens 3 in a 10% sulphuric acid. The cathode was of lead, and the anode of platinum. An apparently tri-molecular hydroquinone (CgH9N)3 was chiefly formed at the cathode, besides small quantities of hydroquinoline (CgHgN) 2 and tetrahydroquinoline, C9H11N2. 

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