A combined continuous microflow photochemistry and asymmetric organocatalysis approach for the enantioselective synthesis of tetrahydroquinolines

• Erli Sugiono and
• Magnus Rueping

Beilstein J. Org. Chem. 2013, 9, 2457–2462, doi:10.3762/bjoc.9.284

• synthesis have been developed. Among the synthetic protocols developed for the preparation of optically active tetrahydroquinolines, the asymmetric hydrogenation of substituted quinolines represents the most widely used and efficient method to prepare this class of N-heterocyclic compound [5][6][7][8][9][10

• optically active tetrahydroquinolines. Readily available substituted 2-aminochalcones were envisioned to undergo photocyclization to the corresponding quinolines which in the presence of a chiral BINOL-derived phosphoric acid diester and Hantzsch dihydropyridine as hydride donor [32][33][34][35][36][37

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• -membered heterocyclic rings in pharmaceutical actives inevitably generates a substantial body of reference material. Consequently this review has been broadly partitioned into six consecutive sections categorised by analogous groupings of heterocyclic rings. The subsections are: Pyridines and quinolines

• . Review 1. Pyridines and quinolines The pyridine ring can be considered as one of the simplest yet most important heteroaromatic structures. Naturally occurring in many important compounds such as the vitamins niacin and pyridoxine, the ubiquitous redox system NADP/NADPH and a number of alkaloids

Synthesis and quantitative structure–activity relationship study of substituted imidazophosphor ester based tetrazolo[1,5-b]pyridazines as antinociceptive/anti-inflammatory agents

• Wafaa M. Abdou,
• Neven A. Ganoub and
• Eman Sabry

Beilstein J. Org. Chem. 2013, 9, 1730–1736, doi:10.3762/bjoc.9.199

• of our continued interest in the development of convenient synthetic approaches to β-enamino- and α-aminophosphonates with anti-inflammatory properties [13][14][15][16][17][18][19][20], we recently successfully synthesized a series of mono- and bisphosphonate-based tetrazolo[1,5-a]quinolines with

Amyloid-β probes: Review of structure–activity and brain-kinetics relationships

• Todd J. Eckroat,
• Abdelrahman S. Mayhoub and
• Sylvie Garneau-Tsodikova

Beilstein J. Org. Chem. 2013, 9, 1012–1044, doi:10.3762/bjoc.9.116

• naphthalene analogues Quinolines Investigation of the quinoline scaffold for imaging in AD has yielded some interesting results, despite there only being a few examples in the literature. The [18F]-labeled 2-fluoroquinolin-8-ol [18F]CABS13 (149) has recently been reported (Figure 5) [98]. The straightforward

Zanthoxoaporphines A–C: Three new larvicidal dibenzo[de,g]quinolin-7-one alkaloids from Zanthoxylum paracanthum (Rutaceae)

• Fidelis N. Samita,
• Louis P. Sandjo,
• Isaiah O. Ndiege,
• Ahmed Hassanali and
• Wilber Lwande

Beilstein J. Org. Chem. 2013, 9, 447–452, doi:10.3762/bjoc.9.47

• , namely isoquinolines represented by benzophenanthridines [8], oxoaporphines [9], aporphines [10] and benzylisoquinoline [11]; and quinolines represented by quinolones [12] and furoquinolines [10]. Others include carbazoles [13], pyrido-indoles [12] and quinazolines [14]. Arylethanamides and amines have

Synthesis of SF₅-containing benzisoxazoles, quinolines, and quinazolines by the Davis reaction of nitro-(pentafluorosulfanyl)benzenes

• Petr Beier and
• Tereza Pastýříková

Beilstein J. Org. Chem. 2013, 9, 411–416, doi:10.3762/bjoc.9.43

• yields. Their synthetic utility was demonstrated by condensation reactions with carbonyl compounds or amines to provide SF5-containing quinolines and quinazolines, respectively. Keywords: benzisoxazoles; pentafluorosulfanyl group; quinazolines; quinolines; sulfurpentafluorides; Introduction Reactions

• has been recently reviewed [28]. In this paper, we report our results on benzisoxazole formation from nitrobenzenes 3 and 4 and further transformations to SF5-containing aminobenzophenones, quinolines and quinazolines. Of these compound types, only some SF5-substituted quinolines are known. Wipf and

• co-workers have recently reported the synthesis of some SF5-substituted quinolines as intermediates towards analogues of the antimalarial agent mefloquine and found that some analogues had improved activity and selectivity against malaria parasites (Scheme 2) [29][30]. Results and Discussion We

Tandem aldehyde–alkyne–amine coupling/cycloisomerization: A new synthesis of coumarins

• Maddi Sridhar Reddy,
• Nuligonda Thirupathi and
• Madala Haribabu

Beilstein J. Org. Chem. 2013, 9, 180–184, doi:10.3762/bjoc.9.21

• )). Similarly, Patil and Raut [24] reported an elegant method for the synthesis of 2-substituted quinolines from 2-aminobenzaldehydes and terminal alkynes by a tandem A3/6-endo-dig-cycloisomerization (Scheme 1, (b)) using a cooperative catalytic system consisting of CuI and pyrrolidine. Prior to these two

Engineering of indole-based tethered biheterocyclic alkaloid meridianin into β-carboline-derived tetracyclic polyheterocycles via amino functionalization/6-endo cationic π-cyclization

• Piyush K. Agarwal,
• Meena D. Dathi,
• Mohammad Saifuddin and
• Bijoy Kundu

Beilstein J. Org. Chem. 2012, 8, 1901–1908, doi:10.3762/bjoc.8.220

• products, i.e., isocryptolepine, δ-carbolines, and α-carbolines; and the indole-based polyheterocycles, i.e., indolo-quinolines, pericyclic indolo-benzazepines, iodo-indoloazepinones, indoloindazole, and azepino-indole [33][34][35][36][37][38][39][40][41][42][43], we were prompted to transform the indole

Continuous-flow catalytic asymmetric hydrogenations: Reaction optimization using FTIR inline analysis

• Magnus Rueping,
• Teerawut Bootwicha and
• Erli Sugiono

Beilstein J. Org. Chem. 2012, 8, 300–307, doi:10.3762/bjoc.8.32

• Magnus Rueping Teerawut Bootwicha Erli Sugiono Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany 10.3762/bjoc.8.32 Abstract The asymmetric organocatalytic hydrogenation of benzoxazines, quinolines, quinoxalines and 3H-indoles in continuous-flow

• -withdrawing or electron-donating groups can be reduced in a continuous fashion and the products 4 were isolated in good yields and with excellent enantioselectivities. Encouraged by the results, we next studied the transfer hydrogenation of quinolines 5 [103][104][105][106]. The optimum reaction temperature

• lower reactivities were obtained. This can be explained by the better heat transfer in the microreactors as compared to the glass flask typically used in our batch reactions. The scope and applicability of the method was then tested on various 2-substituted quinolines (Table 4). In general the

Functionalization of heterocyclic compounds using polyfunctional magnesium and zinc reagents

• Paul Knochel,
• Matthias A. Schade,
• Sebastian Bernhardt,
• Georg Manolikakes,
• Albrecht Metzger,
• Fabian M. Piller,
• Christoph J. Rohbogner and
• Marc Mosrin

Beilstein J. Org. Chem. 2011, 7, 1261–1277, doi:10.3762/bjoc.7.147

• exchange reaction for the regioselective functionalization of quinolines. Thus, the 2,3-dibromoquinoline (65) is regioselectively converted to the 3-magnesiated quinoline derivative 66. Using the same exchange reagent, iPrMgCl·LiCl (64) and 2,4-dibromoquinoline (68), it is now possible to obtain the 4

• regioselectively functionalized quinolines 75 and 78 in 79–88% yield (Scheme 13) [36]. This fine tuning is usually not necessary and numerous Br/Mg-exchange reactions making use of the commercially available reagent iPrMgCl·LiCl (64) have been reported in the literature [31][32][33][34][39]. The use of

Multicomponent reaction access to complex quinolines via oxidation of the Povarov adducts

• Esther Vicente-García,
• Rosario Ramón,
• Sara Preciado and
• Rodolfo Lavilla

Beilstein J. Org. Chem. 2011, 7, 980–987, doi:10.3762/bjoc.7.110

• reactions and practical protocols. Keywords: manganese dioxide; multicomponent reactions; oxidation; Povarov; quinolines; tetrahydroquinolines; Introduction Heterocycles are ubiquitous scaffolds in pharmaceuticals, natural products and biologically active compounds. Quinoline systems in particular

• reaction for library preparation, as one reaction affords several products, when ideally it should give only one. However, these adducts can be subjected to oxidation, which will lead to the corresponding quinolines, preserving the substituents and functionalization already introduced in the preceding MCR

• for these substrates. One of the most commonly used is DDQ, which affords quinolines in acceptable yields. The main advantages of this oxidizing agent lie in its chemoselectivity and a requirement for relatively mild conditions, allowing it to be used in the presence of a wide range of substituents of

Synthesis of 3-(quinolin-2-yl)- and 3,6-bis(quinolin-2-yl)-9H-carbazoles

• Yang Li and
• Wentao Gao

Beilstein J. Org. Chem. 2010, 6, 966–972, doi:10.3762/bjoc.6.108

• significance places this scaffold in a prestigious position. Studies on new quinoline derivatives appear frequently in the chemical literature. Therefore, significant effort continues to be directed toward the development of new quinolines . In particular, there is much current interest in the quinoline ring

• completely satisfactory with regard to operational simplicity, cost of the reagent, drastic reaction conditions, and relatively low yields. Some recent protocols reported for the synthesis of quinolines involve the use of catalysts such as SnCl2 [46], I2 [47], montmorillonite-KSF [48], ionic liquids [49], Bi

• quinolines under mild conditions catalysed by sodium ethoxide. In connection with our studies, we envisioned that the procedure could also be applied to the reaction of 3-acetyl-9-ethyl-9H-carbazole or 3,6-diacetyl-9-ethyl-9H-carbazole with 2-aminoaldehydes or 2-aminoketones, from which the quinolycarbazoles

Quinoline based receptor in fluorometric discrimination of carboxylic acids

• Kumaresh Ghosh,
• Suman Adhikari,
• Asoke P. Chattopadhyay and
• Purnendu Roy Chowdhury

Beilstein J. Org. Chem. 2008, 4, No. 52, doi:10.3762/bjoc.4.52

• dicarboxylic acid, on the contrary, did not produce any excimer upon complexation. This is attributed to the rigidity and steric features of the aromatic diacid that fails to bring the pendant quinolines close enough for excimer formation. We also tested the possibility of excimer formation in the presence of

• ring protons (Figure 14) during complexation with citric acid. The quinoline ring protons (marked with asterisks in Figure 14) suffer a downfield shift upon complexation and led us to presume a weak edge to face type π-stacking interaction between the pendant quinolines. Theoretical calculations on

• interaction brings the pendant quinolines close to exhibit a weak edge to face π-stacking interaction showing the shortest possible distance of 3.48 Å. The hydrogen bond distances are listed in Figure 15a. In comparison, this weak π-stacking interaction between the quinolines is no longer found in the complex