Further exploration of the heterocyclic diversity accessible from the allylation chemistry of indigo

• Alireza Shakoori,
• John B. Bremner,
• Mohammed K. Abdel-Hamid,
• Anthony C. Willis,
• Rachada Haritakun and
• Paul A. Keller

Beilstein J. Org. Chem. 2015, 11, 481–492, doi:10.3762/bjoc.11.54

• through sonication for 30 min at room temperature and then transferred to a septum-equipped flask which contained predried molecular sieves and caesium carbonate under an inert atmosphere. The flask was then plunged into a preheated oil bath (strictly 85–88 °C) and stirred for 30 min, followed by the

Palladium-catalyzed dual C–H or N–H functionalization of unfunctionalized indole derivatives with alkenes and arenes

• Gianluigi Broggini,
• Egle M. Beccalli,
• Andrea Fasana and
• Silvia Gazzola

Beilstein J. Org. Chem. 2012, 8, 1730–1746, doi:10.3762/bjoc.8.198

• degree of regioselectivity (Scheme 9) [56][57]. 3-Arylindoles 10 were selectively achieved on N-acylindoles by using catalytic Pd(TFA)2 and a stoichiometric amount of Cu(OAc)2. The use of additives, such as 3-nitropyridine and caesium pivalate, was proven essential to achieve optimized conditions. It is

Highly selective synthesis of (E)-alkenyl-(pentafluorosulfanyl)benzenes through Horner–Wadsworth–Emmons reaction

• George Iakobson and
• Petr Beier

Beilstein J. Org. Chem. 2012, 8, 1185–1190, doi:10.3762/bjoc.8.131

• less basic potassium or caesium carbonate in acetonitrile could also be used successfully. Finally, we have identified potassium hydroxide as a very inexpensive and convenient base. The best results were obtained by using 1.8 equiv of KOH in acetonitrile. The addition of small amounts of water

Screening of ligands for the Ullmann synthesis of electron-rich diaryl ethers

• Nicola Otto and
• Till Opatz

Beilstein J. Org. Chem. 2012, 8, 1105–1111, doi:10.3762/bjoc.8.122

• ). It turned out that caesium carbonate as a base without addition of molecular sieves did not result in any diaryl ether formation, presumably due to the formation of water inactivating the base. With chemical drying agents such as magnesium sulfate, only trace amounts of the product were obtained. In

An easy α-glycosylation methodology for the synthesis and stereochemistry of mycoplasma α-glycolipid antigens

• Yoshihiro Nishida,
• Yuko Shingu,
• Yuan Mengfei,
• Kazuo Fukuda,
• Hirofumi Dohi,
• Sachie Matsuda and
• Kazuhiro Matsuda

Beilstein J. Org. Chem. 2012, 8, 629–639, doi:10.3762/bjoc.8.70

• water, dried, and concentrated. The residue was dried under reduced pressure and directly subjected to the next reaction. A mixture of caesium palmitate (2.7 g, 7.3 mmol) in DMF (40 mL) was heated at 100–110 °C, to which the DMF solution of the above residue was added slowly. The reaction mixture was

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

• Cécile Verrier,
• Pierrik Lassalas,
• Laure Théveau,
• Guy Quéguiner,
• François Trécourt,
• Francis Marsais and
• Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

• the strong caesium carbonate base led to better results, which was attributed to a better solubility of the base along with a lower solubility of the generated CsI compared to KI salts, preventing an iodide-inhibition effect (Scheme 6). Moreover, copper iodide used as a cocatalyst was able to improve

• underlined the fact that the initial C2-oxazolylcopper formation stays currently unclear. Thus, they suggested a copper-induced reinforcing-acidity effect to facilitate the C2-deprotonation step, which could then be ensured by a very weak base-like caesium fluoride or even by DMF solvent (Scheme 18) [67

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• still-operative palladium complex. To do so, a terminal alkyne and caesium carbonate were added to the reaction mixture containing the newly formed 4-iodopyrrole, and the reaction temperature was increased to 70 °C (Scheme 17) [17]. Grigg and coworkers reported a three-component cascade process for the

Palladium- and copper-mediated N-aryl bond formation reactions for the synthesis of biological active compounds

• Carolin Fischer and
• Burkhard Koenig

Beilstein J. Org. Chem. 2011, 7, 59–74, doi:10.3762/bjoc.7.10

• hindered and functionalized aryl amines [22][23][24]. Aryl bromides are most frequently applied as substrates for the coupling of primary and cyclic secondary amines [17]. In the presence of a weak base such as caesium carbonate, many functional groups are tolerated, while NaOt-Bu has limitations when base

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

Hydroxyapatite supported caesium carbonate as a new recyclable solid base catalyst for the Knoevenagel condensation in water

• Monika Gupta,
• Rajive Gupta and
• Medha Anand

Beilstein J. Org. Chem. 2009, 5, No. 68, doi:10.3762/bjoc.5.68

• Monika Gupta Rajive Gupta Medha Anand Department of Chemistry, University of Jammu, Jammu 180 006, India 10.3762/bjoc.5.68 Abstract The Knoevenagel condensation between aromatic aldehydes and malononitrile, ethyl cyanoacetate or malonic acid with hydroxyapatite supported caesium carbonate in

• water is described. HAP–Cs2CO3 was found to be a highly active, stable and recyclable catalyst under the reaction conditions. Keywords: ethyl cyanoacetate; hydroxyapatite supported caesium carbonate; Knoevenagel condensation; malonic acid; malononitrile; Introduction An area of recent intense

• caesium carbonate (HAP–Cs2CO3) and its effective application to the Knoevenagel condensation between different aromatic aldehydes and malononitrile or ethyl cyanoacetate or malonic acid by stirring in water at 80–100 °C. The products were obtained in high yield and purity. Results and Discussion

Synthesis and properties of calix[4]arene telluropodant ethers as Ag⁺ selective sensors and Ag⁺, Hg²⁺ extractants

• Yang Lu,
• Yuanyuan Li,
• Song He,
• Yan Lu,
• Changying Liu,
• Xianshun Zeng and
• Langxing Chen

Beilstein J. Org. Chem. 2009, 5, No. 59, doi:10.3762/bjoc.5.59

• ][25], caesium ions [26][27][28][29][30], thallium ions [31], lead ions [32][33] and organic ammonium ions [34][35][36]. But only a few reports are concerned with calixarenes as carriers sensitive to transition metal ions in the ionophore-based ISEs [30][37]. Due to their large covalent radius and

Synthesis of new C^α-tetrasubstituted α-amino acids

• Andreas A. Grauer and
• Burkhard König

Beilstein J. Org. Chem. 2009, 5, No. 5, doi:10.3762/bjoc.5.5

• aqueous workup. Entries 1–3 clearly indicate that caesium hydroxide is the base of choice for the conversion of aliphatic aldehydes, which is in contrast to the reactions carried out with aromatic aldehydes where KOH gave the best results [20]. In the next three experiments (entries 4–6), the amount of

• -(tert-butoxycarbonylamino)-4-tert-butoxy-4-oxobutyl]dimethylsulfonium iodide (1, 1.25 g, 2.79 mmol, 1.5 equiv), caesium hydroxide (418 mg, 2.79 mmol, 1.5 equiv) and isobutyraldehyde (5, 169 µl, 1.86 mmol, 1 equiv). The product was purified with a 85:15 mixture of PE:diethyl ether (Rf = 0.2) to give 12

• 329.43. tert-Butyl 3-(tert-butoxycarbonylamino)-2-isobutyltetrahydrofuran-3-carboxylate (13) The synthesis followed GP 1 using [3-(tert-butoxycarbonylamino)-4-tert-butoxy-4-oxobutyl]dimethylsulfonium iodide (1, 1.25 g, 2.79 mmol, 1.5 equiv), caesium hydroxide (418 mg, 2.79 mmol, 1.5 equiv) and 3