Access to pyrrolo-pyridines by gold-catalyzed hydroarylation of pyrroles tethered to terminal alkynes

• Elena Borsini,
• Gianluigi Broggini,
• Andrea Fasana,
• Chiara Baldassarri,
• Angelo M. Manzo and
• Alcide D. Perboni

Beilstein J. Org. Chem. 2011, 7, 1468–1474, doi:10.3762/bjoc.7.170

• pyrrolo[2,3-c]pyridines (Scheme 1) [33]. The reaction provided also the isomeric pyrrolo[3,2-c]pyridines arising from 1,2-migration of the amide moiety. Having recently broadened our studies toward gold catalysis [34][35], we have been intrigued by the investigation of a gold-catalyzed intramolecular

• gold-catalyzed procedure to achieve pyrrolo[2,3-c]pyridines and pyrrolo[3,2-c]pyridines represents a valuable alternative to the Pd-catalyzed cyclization of the analogue allylamides. Experimental General Melting points were determined by capillary method with a Büchi B-540 apparatus and are uncorrected

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

• addition of a catalytic amount of CuCN·2LiCl [7], the arylzinc intermediate is allylated with allyl bromide providing the ester 3 in 94% isolated yield (Scheme 2) [6]. This method can be extended to a broad variety of functionalized heterocyclic iodides such as the pyridines 4 and 7. The corresponding zinc

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• nitriles in the presence of cationic gold catalysts, such as Et3PAuCl/AgSbF6, to give tetrasubstituted pyridines 30 in good yields (Scheme 18) [72]. Cycloadditions initiated by gold-activation of propargyl esters These cycloadditions are a special case of those based on the activation of alkynes and

A practical two-step procedure for the preparation of enantiopure pyridines: Multicomponent reactions of alkoxyallenes, nitriles and carboxylic acids followed by a cyclocondensation reaction

• Christian Eidamshaus,
• Roopender Kumar,
• Mrinal K. Bera and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2011, 7, 962–975, doi:10.3762/bjoc.7.108

• substrate scope and leads to differentially substituted enantiopure pyridines in good to moderate yields. The preparation of diverse substituted lactic acid derived pyrid-4-yl nonaflates is described. Additional evidence for the postulated mechanism of the multicomponent reaction is presented. Keywords

• : allenes; enantiopure pyridines; ketoenamides; multicomponent reactions; nonaflates; Introduction The pyridine core is ubiquitous in pharmacologically active agents, agrochemicals and natural products [1][2][3][4][5]. The HMG-CoA reductase inhibitors Glenvastatin and Cerivastatin are exemplarily mentioned

• as pharmaceuticals that feature the pyridine nucleus [6][7][8][9][10]. Natural products that contain a pyridine ring include the 3-alkylpyridine alkaloid niphatesine C and the fuzanin family [11][12]. Moreover, the ability to form coordination compounds makes pyridines ideal ligands for transition

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• -ynes 282 and non-activated nitriles was introduced by Barluenga and co-workers [148]. The sequence is promoted by both, gold(I) and gold(III) catalysts and leads to the regioselective formation of tetrasubstituted pyridines 289. The initial coordination of the triple bond to the gold catalyst forms

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

Approaches towards the synthesis of 5-aminopyrazoles

• Ranjana Aggarwal,
• Vinod Kumar,
• Rajiv Kumar and
• Shiv P. Singh

Beilstein J. Org. Chem. 2011, 7, 179–197, doi:10.3762/bjoc.7.25

• -dielectrophiles has been extensively used for the preparation of bicyclic nitrogen heterocycles, especially in the preparation of condensed heterocycles such as pyrazolo[3,4-d]pyrimidines, pyrazolo[3,4-b]pyridines, imidazopyrazoles etc. In view of significant interest in the synthesis of these heterocyclics, we

The catalytic performance of Ru–NHC alkylidene complexes: PCy₃ versus pyridine as the dissociating ligand

• Stefan Krehl,
• Diana Geißler,
• Sylvia Hauke,
• Oliver Kunz,
• Lucia Staude and
• Bernd Schmidt

Beilstein J. Org. Chem. 2010, 6, 1188–1198, doi:10.3762/bjoc.6.136

• pyridines as placeholders. Originally, complex G was synthesized as a precursor for mixed NHC-phosphine complexes other than D [25][26][27][28] or, very recently, for the synthesis of Ru-alkylidenes with two different NHC ligands [29]. Comparatively little information is available concerning the catalytic

Design and synthesis of a cyclitol-derived scaffold with axial pyridyl appendages and its encapsulation of the silver(I) cation

• Pierre-Marc Léo,
• Christophe Morin and
• Christian Philouze

Beilstein J. Org. Chem. 2010, 6, 1022–1024, doi:10.3762/bjoc.6.115

• triclinic system, with a pseudo-ternary axis of symmetry. Its coordination sphere involves all 3 nitrogen atoms as well as the 3 oxygen atoms which are implied in the linkage of the pyridines (Figure 3). Bond distances and angles (see Supporting Information File 1) are in accord with those of known silver

Structure and reactivity in neutral organic electron donors derived from 4-dimethylaminopyridine

• Jean Garnier,
• Alan R. Kennedy,
• Leonard E. A. Berlouis,
• Andrew T. Turner and
• John A. Murphy

Beilstein J. Org. Chem. 2010, 6, No. 73, doi:10.3762/bjoc.6.73

• a polymethylene chain linking the two pyridine-derived rings and (ii) the nature of the nitrogen substituents on the 4 and 4′ positions of the precursor pyridines. Restricting the bridge length to two methylene units significantly altered the redox profile, while changes in the nitrogen-substituents

• of the electron pair on the 4-substituent into the pyridine ring. Accordingly, the disalts 21 and 22 were prepared from these 4-substituted pyridines [43][45] and converted into their hexafluorophosphates 21′ and 22′, and then examined by cyclic voltammetry. Each showed a reversible two-electron

Shelf-stable electrophilic trifluoromethylating reagents: A brief historical perspective

• Norio Shibata,
• Andrej Matsnev and
• Dominique Cahard

Beilstein J. Org. Chem. 2010, 6, No. 65, doi:10.3762/bjoc.6.65

• products in high yields. Primary and secondary amines also reacted with 20b to afford N-CF3 products in good yields. Tertiary amines as well as pyridines gave quaternary ammonium and pyridinium salts, respectively. Electrophilic trifluoromethylation could also be achieved by thermal decomposition of 2

Preparation of pyridine-3,4-diols, their crystal packing and their use as precursors for palladium-catalyzed cross-coupling reactions

• Tilman Lechel,
• Irene Brüdgam and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 42, doi:10.3762/bjoc.6.42

• palladium-catalyzed coupling reactions. Fluorescence measurements of the biscoupled products showed a maximum of emission in the violet region of the spectrum. Keywords: bisnonaflates; fluorescence; palladium catalysis; pyridine-3,4-diols; pyridines; Introduction Pyridine scaffolds have been found in

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

Fused bicyclic piperidines and dihydropyridines by dearomatising cyclisation of the enolates of nicotinyl-substituted esters and ketones

• Heloise Brice,
• Jonathan Clayden and
• Stuart D. Hamilton

Beilstein J. Org. Chem. 2010, 6, No. 22, doi:10.3762/bjoc.6.22

• deficient pyridines in the presence of trimethylsilyl triflate, tetrabutylammonium fluoride or a montmorillonite clay. The cyclisation precursor was synthesised by using the procedure of Hayashi [48] employing a Horner–Wadsworth–Emmons olefination between nicotinaldehyde and phosphonate 10. The resulting

A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

• Magnus Rueping and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2010, 6, No. 6, doi:10.3762/bjoc.6.6

• review. A related cationic Ru-vinylidene complex was used for an efficient alkynylation of pyridines with (alkyn-1-yl)trimethylsilane [98]. Based on these preliminary results, various catalytic propargylations of arenes have been developed, employing catalysts such as Mo/chloranil [16

Palladium- catalyzed cross coupling reactions of 4-bromo- 6H-1,2-oxazines

• Reinhold Zimmer,
• Elmar Schmidt,
• Michal Andrä,
• Marcel-Antoine Duhs,
• Igor Linder and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2009, 5, No. 44, doi:10.3762/bjoc.5.44

• -hexyne provided alkynyl-substituted pyridine derivative 12 thus demonstrating the potential of this approach for the synthesis of pyridines. Keywords: alkyne; halogenation; 1,2-oxazines; palladium catalysis; pyridines; Introduction A broad range of synthetic applications demonstrates that 1,2-oxazine

Gold film- catalysed benzannulation by Microwave- Assisted, Continuous Flow Organic Synthesis (MACOS)

• Gjergji Shore,
• Michael Tsimerman and
• Michael G. Organ

Beilstein J. Org. Chem. 2009, 5, No. 35, doi:10.3762/bjoc.5.35

• ., entries a, b, c) and was also useful for the preparation of heterocycle-containing molecules such as pyridines and thiophenes (e.g., entries e–j). A survey of different functional groups revealed a broad tolerance including silyl groups (entries b and h), halides (entries g and i), ethers, (entry c

Trifluoromethyl ethers – synthesis and properties of an unusual substituent

• Frédéric R. Leroux,
• Baptiste Manteau,
• Jean-Pierre Vors and
• Sergiy Pazenok

Beilstein J. Org. Chem. 2008, 4, No. 13, doi:10.3762/bjoc.4.13

• recently in detail on the preparation of O-(trifluoromethyl)dibenzofuranium salts 4 [28][29][30][31] and their use as CF3-transfer agents based on studies of Yagupol'skii [32]. The direct O- and N-trifluoromethylation of alcohols, phenols, amines, anilines and pyridines under mild conditions was described

Electronic differentiation competes with transition state sensitivity in palladium- catalyzed allylic substitutions

• Dominik A. Lange and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2007, 3, No. 36, doi:10.1186/1860-5397-3-36

• -memory effects. [42][43] Computational model systems for P,N-ligands, i.e. PH3 and para-substituted pyridines, have shown that cis-trans differentiations, i.e. the electronic site selectivity, of nucleophilic additions to Pd-η3-allylic intermediates is highest for electron poor pyridine ligands.[45] To

2-Arylhydrazononitriles as building blocks in heterocyclic synthesis: A novel route to 2-substituted- 1,2,3-triazoles and 1,2,3-triazolo[4,5-b]pyridines

• Saleh M. Al-Mousawi and
• Moustafa Sh. Moustafa

Beilstein J. Org. Chem. 2007, 3, No. 12, doi:10.1186/1860-5397-3-12

• reached. It could be also revealed that the formed triazoles are excellent precursors to condensed triazoles and azolyltriazoles. Experimental Section [See Supporting Information File 1] Synthesis of triazolopyridine 8. Synthesis of 1,2,3-triazoles and 1,2,3-triazolo[4,5-b]pyridines. Identification of

Diastereoselective synthesis of some novel benzopyranopyridine derivatives

• Pradeep K. Mohakhud,
• Sujeet M. R. Kumar,
• Vasanth M. R. Kumar,
• Ravi M. R. Kumar,
• Moses D. R. Babu,
• Vyas D. R. K and
• Om D. R. Reddy

Beilstein J. Org. Chem. 2006, 2, No. 25, doi:10.1186/1860-5397-2-25

• of novel N-substituted-1,2,3,4-tetrahydro[1,3]-dioxolo-[6,7]-5H-[1]benzopyrano [3,4-c]pyridines were observed unexpectedly during the acid-mediated ketal removal of ethylenedioxy ketal protected 4-piperidones. The literature revealed that benzopyranopyridine derivatives are of scientific interest and

• phenols and mesylate derivatives, unexpectedly resulted in cyclodehydration leading to new benzopyrano derivatives, N-substituted-1,2,3,4-tetrahydro[1,3]-dioxolo-[6,7]-5H-[1]benzopyrano [3,4-c]pyridines. The process involves the deprotection of the carbonyl protecting group, and then the cyclization

• reaction occurs followed by dehydration to give the final product. These N-substituted-1,2,3,4-tetrahydro[1,3]-dioxolo-[6,7]-5H-[1]benzopyrano [3,4-c] pyridines were dealkylated giving the corresponding N-unsubstituted derivatives. The cis-1,3,4,4a,5,10b-hexahydro-[6,7]-2H-[1]benzopyrano [3,4-c]pyridine

The Elbs and Boyland- Sims peroxydisulfate oxidations

• E. J. Behrman

Beilstein J. Org. Chem. 2006, 2, No. 22, doi:10.1186/1860-5397-2-22

• Intermediate with the Hydroxide Ion. A Catalytic Cycle for Peroxydisulfate Consumption. A Non-catalytic cycle for Peroxydisulfate Consumption. Oxidation of phenols Oxidation of anilines Oxidation of coumarins Oxidation of xanthones Oxidation of flavones Oxidation of pyridines Oxidation of pyrimidines Oxidation

ADDP and PS-PPh₃: an efficient Mitsunobu protocol for the preparation of pyridine ether PPAR agonists

• Paul S. Humphries,
• Quyen-Quyen T. Do and
• David M. Wilhite

Beilstein J. Org. Chem. 2006, 2, No. 21, doi:10.1186/1860-5397-2-21

• . As expected, oxazoles, thiazoles, pyrazoles, and pyridines are tolerated in this chemistry. In a limited number of cases, functionality (e.g. basic amines, benzimidazoles, indoles, etc.) caused no reaction to occur and only recovered starting materials were isolated (data not shown). We then shifted

Efficient synthesis of 5-substituted 2-aryl- 6-cyanoindolizines via nucleophilic substitution reactions

• Eugene V. Babaev,
• Natalya I. Vasilevich and
• Anna S. Ivushkina

Beilstein J. Org. Chem. 2005, 1, No. 9, doi:10.1186/1860-5397-1-9

• according to protocol of Gevald.[6] Our modification of the original method included separation of N- and O-isomers of phenacyl pyridines before cyclization (using the difference in their solubility in chloroform). Although 1H-NMR (see Supporting Information File 2) and Nuclear Overhauser Effect confirmed