The simplest member of the quinoline family is quinoline itself, a compound having molecular structure C9H7N. Quinolines carrying a mercapto group on the benzo ring exist in the zwitterion or the zwitterion extended quinone form to a larger extent than do the analogous hydroxy compounds 〈63AHC(S1)400〉. The synthesis of quinoline derivatives using metal catalyzed processes continues to be of interest. The annulation of quinolines with a propargylic moiety at the 2 position occurs (i) by metal catalysis (Cu, Pt, Pd, In, Au, Ag), (ii) under metal-free conditions (I2), or (iii) in the presence of protic solvents. Recent advances in the synthesis of the Martinelline alkaloids are also described. Cycloadditions of alkenes to pyridines will be considered later in Section 2.05.7. The formation of 6-sulfamoylquinoline-4-carboxylic acids was reported using Pfitzinger conditions. [10] The only report of quinoline as a natural product is from the Peruvian stick insect 1958 Oct;291/63(10):493-502. Since 2009, Tutorsglobe has proactively helped millions of students to get better grades in school, college or university and score well in competitive tests with live, one-on-one online tutoring. Acridine is cleanly hydrogenated in both benzene rings over platinum oxide in trifluoroacetic acid at 50 psi 〈75JOC2729〉. Various methods for the functionalization of quinolines were also investigated. However, when the reduction is performed over Raney nickel at 100 °C, one benzene ring only is hydrogenated and 1,2,3,4-tetrahydroacridine is obtained 〈41JA1563〉. The major metabolic enzyme is the CYP2E1 isoform with the primary end product from this reaction being 3-hydroxyquinoline. Fig: General types of Reaction of Quinoline. Pyridine has found use as a solvent, base, ligand, functional group, and molecular scaffold. Quinolines may be obtained by the Skraup synthesis. This approach can also be applied to the synthesis of 1-trimethylsilylethynyl-1,2-dihydroisoquinoline 75, which are formed in good yields. Quinoline is a slightly weaker base (pKa 4.9) as compare to pyridine (pKa 5.2). Compare with Skraup. [Article in German] ZINNER H, FIEDLER H. Quinolines are often synthesized from simple anilines using a number of named reactions. Quinoline is only slightly soluble in cold water however dissolves readily in hot water and most organic solvents. Quinolines 76 (Scheme 34) were reacted with various diazocarbonyl compounds 77 in the presence of copper(II) triflate to generate the seven-membered azepine ring system 78 in good yields. We use cookies to help provide and enhance our service and tailor content and ads. Methods for the synthesis of quinoline bearing fluorine or difluoromethyl substituents were the focus of various reports. T. M. Gøgsig, A. T. Lindhardt, T. Skrydstrup, Org. Moreover, by comparison by its aromatic analogue naphthalene, one would expect position 3 to be comparatively unreactive. [8] Its principal use is as a precursor to 8-hydroxyquinoline, which is a versatile chelating agent and precursor to pesticides. Hydrogenation of benzo[h]quinoline over platinum oxide in trifluoroacetic acid at 50 psi gives 5,6,6a,7,8,9,10,10a-octahydrobenzo[h]quinoline (55) as the main product (63%) together with 7,8,9,10-tetrahydrobenzo[h]quinoline (56) (5%) and 1,2,3,4,5,6,7,8-octahydrobenzo[h]quinoline (57) (28%) (Equation (23)) 〈75JOC2729〉. Whenever the temperature is allowed to increase to -45ºC the adduct rearranges to 4-amino-3,4-dihydroquinoline and on oxidation this product provides 4-aminoquinoline. Fluorination at position 3 completely prevents the mutagenicity of quinoline. [12] (C.f. For this reason, borohydride reductions of these heterocyclic compounds are usually performed in acidic conditions using sodium cyanoborohydride, allowing the formation uniquely of the corresponding 1,2,3,4-tetrahydroisoquinolines (Scheme 9).1, Alternatively, it has been demonstrated that the preparation of 1,2,3,4-tetra-hydroisoquinolines from quinolines can also be promoted under Lewis acidic conditions with reducing systems such as sodium borohydride–nickel(II)chloride,7 sodium cyanoborohydride–boron trifluoride etherate,8 or zinc borohydride.9, Florea Dumitrascu, ... Mino R. Caira, in Advances in Heterocyclic Chemistry, 2019. Expand your confidence, grow study skills and improve your grades. In supramolecular chemistry, pyridines link metal organic frameworks and pyridinium salts provide cationic structures for nanodevices. Notably, Piatnitski and coworkers reported that the reaction of (2-trifluoromethyl)aniline 73 with esters of arylacetic acids produced 4-fluorinated quinolinones 74 <04OL4061>. From: Comprehensive Heterocyclic Chemistry, 1984, DAVID GINSBURG, in Concerning Amines, 1967. Fig: Reaction of Quinoline with Acetyl Nitrate, Fig: Reaction of Quinoline with Fuming Nitric Acid. Reaction of DMAD with 6,7-dimethoxy-2H-1,3-benzothiazine, pyridazines or their 4,5-benzologues, 2,4-dimethylquinazoline, quinoxaline, and quinazolines furnished derivatives of the 3,4-benzologue of (6) 〈82H(19)489〉, (9) 〈66JCS(C)2218〉 and its 3,4-benzologue 〈68RRC513, 79JCR(S)394〉, the 7,8-benzologue of (10) 〈68JCS(C)926〉, the 3,4-benzologue of (11) 〈72MI 823-03〉, and the 3,4-benzologue of (12) 〈75JCS(P1)2322, 75KGS1701, 80H(14)1959〉. 200, 2493–2500). ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. URL:, URL:, URL:, URL:, URL:, URL:, URL:, URL:, URL:, URL:, Comprehensive Heterocyclic Chemistry, 1984, V. Ratovelomanana-Vidal, ... M.R.