Benzo quinoline-6-carboxylic acid

The acid-catalyzed hydrolysis continues to be used as a highly satisfactory method for the synthesis of quinaldic acids. The reaction of Reissert compound (7) with hydrobromic acid in acetic acid gave near quantitative yields of quinaldic acid hydrobromide with no contamination from other acid derivatives and would appear to be the method of choice for this conversion. This method has subsequently been used to produce high yields of benzo(/)quinoline-3-carboxylic acid and phthalazine-1-carboxylic acid. ... 

The ring closure of diethyl (benzo[/]quinolin-l-yl)methylenemalonate (148) was carried out by heating in polyphosphoric acid at 90-110°C to give ethyl naphtho[ 1,2,3-//]quinolizine-6-carboxylate (723) (84USP4456606). 

Permanganate oxidation of the benzo[c]quinolizinium ion (Scheme 35) likewise involves attack of the quinolizinium nucleus to produce quinoline-2-carboxylic acid. Similar behavior is shown by the 10-nitrobenzo[c]quinolizinium ion (71JCS(C)3650). 

Benzo[6]thiophene carboxylic acids have been decarboxylated byT heating them with oxalic acid,254 by heating the ester with IN NaOH in dioxane,441 by heating the barium salt with barium hydroxide in vacuo,162, by heating them in quinoline with copper chromite347, 352.353 or> preferably, with copper,109 185 189,298 315 343 344 351 412 422, 638 an(j py heating them alone in quinoline54 or pyridine.114... 

Improved conditions for the synthesis of benzo[6]thiophene-2-carboxylic acids 16 from the readily available P-aryl-a-mercaptoacrylic acids 17 under microwave irradiation have been described. The products 16 could be further decarboxylated to the corresponding benzo[Z>]thiophenes imder microwave conditions in quinoline <04TL9645>. 

The classical decarboxylation of benzo[fo]thiophene-2-carboxylic acids involves a Cu-mediated reaction in quinoline and a subsequent problematic work-up. A new homogeneous method was developed and adapted under the action of microwave irradiation by using an organic base (DBU) and a high-boiling polar solvent (dime-thylacetamide). All the decarboxylations (65-100%) were performed at 200 °C for 45 min in a sealed microwave vessel at 600 W (Scheme 10.14) [31]. 

Other 1,2-diazines synthesized included 4-amino-3-cinnolinecarboxylic acids <97PHA91 >, I -aryl-6-chloro-l,4-dihydro-4-oxothieno[2,3-c]pyridazine-3-carboxylic acids <97JPR284>, 2H-benzo[2,3-g]pyridazino[4,5-<7,e]quinolin-3-ones <97M681>, 3-chloro-4-carbamoyl-5-aryl-6-methylpyridazine N-oxides <97F67>, 2-aroyl-6-(hetero substituted)-3(2//)-pyridazinones <97HCM267>, and 5-(4-hydroxycinnolin-3-yl)tetrazoles 2-methyl-5-(4-acetoxycinnolin-3-yl)-... 

The increased potency of the pyrido 2,3-d]pyrimidine ester (111) and the achievement of oral activity with the benzo[ quinazoline ester (V) suggested the preparation of 3,4-dihydro-4-oxopyrimido[4,5-b]quinoline-2-carboxylic acid (VI) and its corresponding ethyl ester (VII) which combine the features of III and V. This new acid and ethyl ester exhibit PCA activity 4 to 8 times that of DSCC and thus are about 50 to 100 times... 

Selective hydrogenation. A mixture of benzo [f] quinoline-3-carboxylic acid, PtOg, and 15%-HGl hydrogenated at 50-60° and 3-4 atm. until the theoretical amount of Hg has been taken up after 2 hrs. l,2,3,4-tetrahydrobenzo[f]quinoline-3-carboxylic acid hydrochloride. Y ca. 100%. F. D. Popp and W. R. Schleigh, J. Heterocyclic Ghem. 1, 107 (1964). 

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