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

• same genus as rich in alkaloids [3][4][5], which constitute the most abundant class of compounds in this genus, while coumarins [6], lignans [3] and triterpenoids, especially limonoids [7], are the minor constituents. Different classes of alkaloids have been found and reported from Zanthoxylum species

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

• , pyrrolidine and salicylaldehydes led to a concomitant cycloisomerization followed by hydrolysis of the resultant vinyl ether to afford coumarins in a cascade process. The reaction proceeded through exclusive 6-endo-dig cyclization and is compatible with halo and keto groups giving coumarins in good to

• catalyst. That, after consecutive A3 coupling, cycloisomerization and hydrolysis of the resultant vinyl ether intermediate, should produce coumarins (Scheme 1, (d)). The reason for the selective 6-endo-dig cyclization of such a cooperative-catalysis reaction has been well documented through DFT

• computational studies by Patil et al. in their recent publication [32]. Results and Discussion Coumarins [33][34][35][36][37][38][39][40][41][42][43][44][45][46] have been attractive targets [47][48][49][50][51][52][53] for synthetic chemists due to their frequent occurrence in nature and for their interesting

Cyclization of ortho-hydroxycinnamates to coumarins under mild conditions: A nucleophilic organocatalysis approach

• Florian Boeck,
• Max Blazejak,
• Markus R. Anneser and
• Lukas Hintermann

Beilstein J. Org. Chem. 2012, 8, 1630–1636, doi:10.3762/bjoc.8.186

• Florian Boeck Max Blazejak Markus R. Anneser Lukas Hintermann Department Chemie, Technische Universität München, Lichtenbergstr. 4, 85748 Garching, Germany 10.3762/bjoc.8.186 Abstract (E)-Alkyl ortho-hydroxycinnamates cyclize to coumarins at elevated temperatures of 140–250 °C. We find that the

• use of tri-n-butylphosphane (20 mol %) as a nucleophilic organocatalyst in MeOH solution allows cyclization to take place under much milder conditions (60–70 °C). Several coumarins were prepared, starting from ortho-hydroxyarylaldehydes, by Wittig reaction with Ph3P=CHCO2Me to (E)-methyl ortho

• -hydroxycinnamates, followed by the phosphane catalyzed cyclization. Keywords: catalysis; coumarins; heterocycles; mechanisms; organocatalysis; phosphanes; Introduction Coumarins are important structural motifs in natural products and bioactive compounds, in which they exhibit broad biological activity, e.g., as

Palladium-catalyzed substitution of (coumarinyl)methyl acetates with C-, N-, and S-nucleophiles

• Kalicharan Chattopadhyay,
• Erik Fenster,
• Alexander J. Grenning and
• Jon A. Tunge

Beilstein J. Org. Chem. 2012, 8, 1200–1207, doi:10.3762/bjoc.8.133

• the biologically active coumarin motif. This new method was utilized to prepare a 128-membered library of aminated coumarins for biological screening. Keywords: benzylation; catalysis; coumarin; chemical diversity; decarboxylative; palladium; substitution; Introduction Coumarins are privileged

• nucleophiles by using palladium(0) as a catalyst (Scheme 1). In addition, given the known biological activity of aminomethylcoumarins, we prepared a 128-member library of aminated coumarins using rapid automated synthesis. Results and Discussion To begin investigating the diversification of

• . Importantly, selective monobenzylation was achieved for each example. Regarding the coumarin moiety, the decarboxylative coupling was compatible with a variety of simple substitutions, including methoxy (2c,d,g,h), chloro (2g,h) and naphthyl (2e) coumarins. While the decarboxylative coupling worked well for

Dioxane dibromide mediated bromination of substituted coumarins under solvent-free conditions

• Subrata Kumar Chaudhuri,
• Sanchita Roy and
• Sanjay Bhar

Beilstein J. Org. Chem. 2012, 8, 323–329, doi:10.3762/bjoc.8.35

• /bjoc.8.35 Abstract An efficient solvent-free protocol for regioselective bromination of substituted coumarins has been developed by using dioxane dibromide as the solid brominating agent. The efficacy of the solvent-free protocol has been established. The effects of the electronic nature and location

• of the substituents on the outcome of the reaction have been rationalized with a proposed mechanism. Keywords: coumarins; solvent-free reaction; substituents; vinylic bromination; Introduction Brominated coumarins have immense synthetic, biological and industrial importance due to their occurance

• diseases [4]. Halocoumarins also exhibit insecticidal and fungicidal properties [5]. A few methods have been documented for regioselective bromination of coumarins, which include CuBr2/Al2O3 in bromobenzene under reflux [5], Br2 in glacial AcOH [6], Br2/Al2O3 under microwave irradiation [7], NBS in CHCl3

Synthesis and characterization of new diiodocoumarin derivatives with promising antimicrobial activities

• Hany M. Mohamed,
• Ashraf H. F. Abd EL-Wahab,
• Ahmed M. EL-Agrody,
• Ahmed H. Bedair,
• Fathy A. Eid,
• Mostafa M. Khafagy and
• Kamal A. Abd-EL-Rehem

Beilstein J. Org. Chem. 2011, 7, 1688–1696, doi:10.3762/bjoc.7.199

• -diiodosalicylaldehyde; diethyl malonate; ethyl cyanoacetate; coumarins; Michael reaction; Introduction Coumarins and their derivatives are biologically and pharmaceutically interesting compounds known for their use as additives in food, perfumes, cosmetics, pharmaceuticals, platelet aggregation and agrochemicals [1][2

• ]. Coumarins have also been reported to exhibit several biological activities, such as antimicrobial, anticancer, antifungal, anti-HIV and antioxidant properties [3][4][5][6], and they also served as versatile precursors for many organic transformations in the synthesis of a number of drug-like molecules [7][8

Synthesis of coumarin or ferrocene labeled nucleosides via Staudinger ligation

• Ivana Kosiova,
• Andrea Janicova and
• Pavol Kois

Beilstein J. Org. Chem. 2006, 2, No. 23, doi:10.1186/1860-5397-2-23

• ), which were synthesised in our department as part of studies into new ligands. Coumarins as fluorescent probes or labels [28][29][30] have extensive and diverse applications, they exhibit extended spectral range, are photostable and have high emission quantum yields. Ferrocene derivatives are often used

• ligations depends on the structure of the carboxylic acid and on the azido group position on the nucleoside. Addition of water to the proposed intermediates I-IV (Scheme 2) resulted not only in the formation of the desired products, but also in the formation of 4-methyl coumarins 15a-c and aminonucleosides

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