Quinoline bromination

A quinoline—bromine adduct in hot carbon tetrachloride containing pyridine gives a 90% yield of 3-bromoquinoline (21) 3-chloroquinoline [612-59-9] is prepared by an analogous route, but in poorer yield. A quinoline—aluminum chloride complex heated with bromine gives a 78% yield of 5-bromoquinoline [165-18-3] (22). Equal quantities of 5- and 8-bromoquinoline [16567-18-3] are formed when quinoline is treated with one equivalent of bromine in concentrated sulfuric acid containing silver sulfate (23). 

Bromination of quinoline in sulfuric acid containing silver sulfate gives in good yield almost equal amounts of 5- and 8-bromoquinoline. With an excess of bromine and silver sulfate 5,8-dibromoquinoline becomes the major product. The dibromo compound is similarly formed from 5- and 8-bromoquinoline. Further bromination gives 5,6,8-tribromoquinoline (Scheme 7). With 3-bromoquinoline as starting material, formed, for example, from bromine in carbon tetrachloride (see Chapter 2.05), the silver sulfate/sulfuric acid method converts it into 3,5-dibromo- and 3,5,8-tribromo-quinoline. Bromination with... 

Charge transfer (CT) complexes, different from aromatic ketone/amine systems, such as quinoline-bromine, pyridine-bromine, tetrahydrofuran-bromine etc. have also been reported to behave as initiators of vinyl polymerization, particularly under photoactivation [65-68]. 

Whereas in the MMA photoinitiated polymerization by quinoline-bromine CT complex the formation of radicals is preceded by an instantaneous complexation reaction between the CT complex initiator and the monomer [68], no evidence of this occurrence is observed in the case of the poly(NVC)-Br2 CT complex, probably due to the steric hindrance provided by the polymeric chain. The behaviour of the above system should however be compared with that of the corresponding low-molecular-weight A-alkyl carbazole-Bra CT complex in order to clarify this point. 

A quinoline-bromine charge transfer complex has been found to be particularly effective for producing copolymers of styrene... 

MMA has also been polymerized by photoinitiation with iodine,8 iodine-monoethanolamine mixtures, quinoline-bromine charge-transfer complexes,10 and quinoxaline derivatives.11 The initiation with iodine was not attributed to simple dissociation of molecular iodine, but rather to absorption by an iodine-monomer (M) complex [reaction (3)]. A 1 1 complex between Ia and mono-... 

This linear coordination, but with unequal I—bonds, has been found in the compound (bipy)(IN3)2 ° where the I—N(bipy) distance averages 2.44 A and I—N(azide) averages 2.17 A, reflecting the difference in the bonding to the two ligands. The two bromine(I) examples studied both show asymmetry of the N—Br—linear system, although the two ligands are equivalent. Thus in bis(quinuclidine)bromine(I) tetrafluoroborate the Br— distances are 2.120 and 2.156 A and in bis(quinoline)bromine(I) perchlorate they are 2.100 and 2.165 A. The reason for the asymmetry is not obvious. 

P. Ghosh, P.S. Mitra, Photopolymerization of methyl methacrylate by use of a quinoline-bromine charge transfer complex as the photoinitiator, J. Polym. Sci., Polym. Chem. Ed. 13 (1975) 921-930. 

This coupling works best when the halogen at the 7-position is bromine rather than chlorine or fluorine. This represents the first appUcation of this coupling reaction to the intact quinoline nucleus and thus represents an important advance in quinolone chemistry. 

Treatment of quinoline with cyanogen bromide, the von Braun reaction (17), in methanol with sodium bicarbonate produces a high yield of l-cyano-2-methoxy-l,2-dihydroquinoline [880-95-5] (5) (18). Compound (5) is quantitatively converted to 3-bromoquinoline [5332-24-1], through the intermediate (6) [66438-70-8]. These conversions are accompHshed by sequential treatment with bromine in methanol, sodium carbonate, or concentrated hydrochloric acid in methanol. Similar conditions provide high yields of 3-bromomethylquinoHnes. 

Quinoline, 2,4-bis(dimethylamino)-synthesis, 2, 419, 469 Quinoline, 3-bromo-bromination, 2, 319 oxidation, 2, 325 Skraup synthesis, 2, 467 Quinoline, 5-bromo-bromination, 2, 319 nucleophilic substitution, 2, 324 Quinoline, 6-bromo-nucleophilic substitution, 2, 324 Quinoline, 8-bromo-bromination, 2, 319 N-oxide... 

Hydroxyquinoline forms the complex with Cu(II) in ratio 1 1 at pH 5-7. The composition of the complex is changed on 1 2 at pH>7. 8-Hydroxy-quinoline accepts bromine therefore its excess has been removed with NaOH solution. The complex was extracted with chloroform. It was shown that double extraction was enough to extract the complex. The detection limit is 5x10 M during 10c and at current generation IxlO A. 

Deca/octahydro 6-alkyloxazolo /-fused quinolines 17 were prepared and evaluated as dopaminergics (87EUP1). A series of linearly annelated 8-alkyl-deca/ octahydrooxazoloquinolines 18 and their salts were prepared for use as dopamine D2-agonists and hypertensive agents. The rran.s-( )-l-propyl-6-oxodecahydro-quinoline was brominated, then treated with urea in methanol to give the 2-amino... 

It is difficult to treat the effect of a heteroatom on the localization energies of aromatic systems, but Brown has derived molecular orbital parameters from which he has shown that the rates of attack of the phenyl radical at the three positions of pyridine relatively to benzene agree within 10% with the experimental results. He and his co-workers have shown that the formation of 1-bromoisoquinoline on free-radical bromination of isoquinoline is in agreement with predictions from localization energies for physically reasonable values of the Coulomb parameters, but the observed orientation of the phcnylation of quinoline cannot be correlated with localization ener-... 

Bromination of the diphenyl indole derivative 316 with bromine in DMF or trimethylammonium bromide afforded the 7-bromo derivative 317. Reaction with allyl bromide or its derivatives gave A-allyl derivatives 318 that upon cyclization with palladium acetate gave 7,9-dimethoxy-l,2-diphenylpyrrolo[3,2,l-// ]quinoline derivatives 319 (92T7601) (Scheme 57). 

Bromination. Neutral bromination of quinoline (66) using bromine in hot carbon tetrachloride and pyridine gave the 3-bromo derivative (68) (90%) and 3,6-dibromoquinoline (69) (2%), along with traces of 3,8-di-and 3,6,8-tri-bromo products [59CI(L) 1449 66AHC(7)1]. There is some... 

With acetic acid as solvent 68 is still the major product (Scheme 32). The minor product (69) probably forms in preference to the 3,5-isomer because the quinoline free base is reacting the high yield of 68 can be rationalized in terms of a 1,4- or 1,2-addition product that is rapidly bromi-nated at C-3. The 6- and 8-positions substitute more slowly [62JCS283, 62JCS291 77HC(32-1)319]. Both the 6- and the 8-bromoquinolines were 3-brominated under neutral conditions (62JOC1318). 

Reactions in acetic anhydride with metal acetates present probably occur by 1,4-addition of bromonium acetate (85CHE458). When NBS in sulfuric acid at 20°C was used, the product ratio resembled that observed with bromine-sulfuric acid-silver sulfate. At 60°C the ratio changed to 2 1.2 1 as a consequence of more extensive dibromination (88CHE892) (Scheme 33). As might have been deduced, 2-(2 -thienyl)quinoline was brominated only in the thiophene ring (82CHE28). 

Bromine in acetic acid readily converted the activated 3-hydroxy-quinoline into its 4-bromo derivative (76%) under similar conditions 8-hydroxyquinoline gave a mixture of the 5-bromo and 5,7-dibromo compounds [71BAU400 72JOC4078]. All of the possible monobromo derivatives of the latter substrate have been made (91M935). 4-Hydroxy-... 

Vapor phase brominations have given rise to varying products dependent on the reaction temperature. At 300°C bromine converted quinoline in the presence of pumice into 68 (25%) at 450°C 2-bromoquinoline (25%) became the major product at 500°C the yield of the 2-bromo isomer increased to 53%, but there was some dibrominated material [77HC(32-1)319]. The absence of 3-bromoquinoline at the higher temperatures could be accounted for in terms of radical attack, or it could be due to thermal instability of that isomer [59CI(L)1449]. 

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