Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• , 25 °C for aldimine formation (first step) in the MM K-10 containing packed-bed capillary reactor (PBCR), and 80 °C for the reaction with phenylacetylene (second step) in Au NP@Al2O3 containing PBCR. The system, tested with some different aryl/heteroaryl/alkylaldehydes and cyclic/acyclic secondary

Synthesis, characterization and initial evaluation of 5-nitro-1-(trifluoromethyl)-3H-1λ³,2-benziodaoxol-3-one

• Nico Santschi,
• Roman C. Sarott,
• Elisabeth Otth,
• Reinhard Kissner and
• Antonio Togni

Beilstein J. Org. Chem. 2014, 10, 1–6, doi:10.3762/bjoc.10.1

• . Consequently in light of these results, DSC measurements of 2 and 3 were carried out in order to assess the thermal stability of the new derivative. These measurements were performed in punctured Al2O3 pans with a heating rate of 10 K/min. For reagent 2, a decomposition energy of 138 kJ/mol (438 J/g, slightly

Investigating the continuous synthesis of a nicotinonitrile precursor to nevirapine

• Ashley R. Longstreet,
• Suzanne M. Opalka,
• Brian S. Campbell,
• B. Frank Gupton and
• D. Tyler McQuade

Beilstein J. Org. Chem. 2013, 9, 2570–2578, doi:10.3762/bjoc.9.292

• included two columns: a packed-bed of Al2O3 to catalyze the reaction and a packed bed of 3 Å molecular sieves to absorb water before the addition of DMF-DMA (Scheme 4). The mass of each solid used (2.00 g of Al2O3 and 1.50 g molecular sieves) was chosen based on the size of the available columns. Assuming

• that the Knoevenagel condensation occurred primarily in the Al2O3 column, we only varied the temperature of the Al2O3 column. The Al2O3 column temperature was initially set to 25 °C which yielded 91% of 5 from acetone and malononitrile (Table 2, entry 2). We observed that the Al2O3 column reactor

• are combined the system stability can become an issue. To measure the stability, we ran the reaction under the optimized conditions and monitored the product distribution. When the aforementioned optimized column temperatures were used (20 °C Al2O3 column, 25 °C 3 Å MS column), the alumina column

Asymmetric synthesis of a highly functionalized bicyclo[3.2.2]nonene derivative

• Toshiki Tabuchi,
• Daisuke Urabe and
• Masayuki Inoue

Beilstein J. Org. Chem. 2013, 9, 655–663, doi:10.3762/bjoc.9.74

• column of Al2O3 with Et2O. The filtrate was concentrated. The residue was purified by flash column chromatography (silica gel 120 g, pentane/Et2O 10:1 to 5:1) to afford diene 14 (1.5 g, 11 mmol) in 69% yield: yellow oil; IR (neat) νmax: 2949, 1656, 1595, 1431, 1377 cm−1; 1H NMR (500 MHz, CDCl3) δ 1.92

Reactions of salicylaldehyde and enolates or their equivalents: versatile synthetic routes to chromane derivatives

• Ishmael B. Masesane and
• Zelalem Yibralign Desta

Beilstein J. Org. Chem. 2012, 8, 2166–2175, doi:10.3762/bjoc.8.244

• of salicylaldehyde (5) with dimedone (18) in the presence of a catalytic amount of KF/Al2O3 (Scheme 6) [21]. The reaction is thought to proceed through a Knoevenagel condensation, a Michael addition and an intramolecular cyclization. The reaction was repeated with chloro-, bromo-, dichloro-, dibromo

• prepared in good yields by employing nitro-, methoxy-, and chloro-substituted salicylaldehydes instead of 38. Other solid catalysts such as 4 Å molecular sieves, 5 Å molecular sieves and Al2O3 were found to be effective in catalyzing the reaction but resulted in lower yields (50–63%) of product 39 [32

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

• furnished the tetrabromide 207, which on hydrolysis (H2O, Al2O3) provided the dibromo diol 208 [138]. A careful study of the oxidation of several conjugated bisallenes with different oxidants has been carried out by Pasto and co-workers [139]. As summarized in Scheme 50, the tetramethylbisallene 24 yields

Approaches to α-amino acids via rearrangement to electron-deficient nitrogen: Beckmann and Hofmann rearrangements of appropriate carboxyl-protected substrates

• Sosale Chandrasekhar and
• V. Mohana Rao

Beilstein J. Org. Chem. 2012, 8, 1393–1399, doi:10.3762/bjoc.8.161

• ), their carboxyl groups being masked as a 2,4,10-trioxaadamantane unit (an orthoacetate). The oxime mesylates have been rearranged with basic Al2O3 in refluxing CHCl3, and the malonamic acids with phenyliodoso acetate and KOH/MeOH. Both routes are characterized by excellent overall yields. Structure

• rearrangement of 3 to the N-benzoyl derivative 5 is accomplished (generally) in high overall yields via a two-step sequence: Methanesulfonylation to compounds 4, which are heated under reflux in CHCl3 in the presence of basic Al2O3 (Table 1) [17]. The formation of the desired N-benzoyl

• bubbled in over 0.5 h. The mixture was stirred at room temperature for 6 h and the volatiles removed in vacuo. The residue was treated with water and worked up with CH2Cl2, etc., the crude products being purified by neutral Al2O3 (grade 1) column chromatography. Hofmann rearrangement of 9 to final

Synthesis of new pyrrole–pyridine-based ligands using an in situ Suzuki coupling method

• Matthias Böttger,
• Björn Wiegmann,
• Steffen Schaumburg,
• Peter G. Jones,
• Wolfgang Kowalsky and
• Hans-Hermann Johannes

Beilstein J. Org. Chem. 2012, 8, 1037–1047, doi:10.3762/bjoc.8.116

• solvent was removed. The raw product was preadsorbed onto aluminium oxide, activity III. Column chromatography (Al2O3, activity III, dichloromethane/ethyl acetate/hexane 1:1:2 → dichloromethane/ethyl acetate 1:1, Rf (Al2O3, dichloromethane/ethyl acetate/hexane 1:1:2) = 0.27) gave 2 as a pale yellow solid

Catalyst-free and solvent-free Michael addition of 1,3-dicarbonyl compounds to nitroalkenes by a grinding method

• Zong-Bo Xie,
• Na Wang,
• Ming-Yu Wu,
• Ting He,
• Zhang-Gao Le and
• Xiao-Qi Yu

Beilstein J. Org. Chem. 2012, 8, 534–538, doi:10.3762/bjoc.8.61

• . Surprisingly, a great quantity of Michael product 3a was obtained after 5 min of grinding. Then a number of powdered substances were screened, such as KBr, quartz sand, Al2O3, kieselguhr, active carbon, and so on. From Figure 1, it was found that all tested grinding aids could promote the reaction to different

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

• 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

Efficient and selective chemical transformations under flow conditions: The combination of supported catalysts and supercritical fluids

• M. Isabel Burguete,
• Eduardo García-Verdugo and
• Santiago V. Luis

Beilstein J. Org. Chem. 2011, 7, 1347–1359, doi:10.3762/bjoc.7.159

• , enhanced selectivity. Some classical examples are provided by the work of Baiker [38][39]. Thus, initial studies focused on the enantioselective hydrogenation of ethyl pyruvate to (R)-ethyl lactate over cinchonidine (CD) modified Pt/Al2O3. The results obtained showed that a dramatic increase in both

• provided by the group of Poliakoff [40][41]. In this case, the reaction studied was the hydrogenation of dimethyl itaconate over a chiral Rh catalyst on an inorganic support (Al2O3) with a phosphotungsten acid linker (Scheme 2). It is important to take into consideration a direct comparison with the work

• reported by Poliakoff and Sheldon involving two sequential reactions (Scheme 8) [94]. In that case, the first step was the continuous hydrogenation of acetophenone to afford the racemic phenylethanol with Pd supported on SiO2/Al2O3 as the catalyst and scCO2 as the reaction medium (150–200 °C, 10 MPa, 1.1

Functionalization of anthracene: A selective route to brominated 1,4-anthraquinones

• Kiymet Berkil Akar,
• Osman Cakmak,
• Orhan Büyükgüngör and
• Ertan Sahin

Beilstein J. Org. Chem. 2011, 7, 1036–1045, doi:10.3762/bjoc.7.118

• anhydrous sodium sulfate and concentrated under reduced pressure. After the residue was passed through a short Al2O3 (neutral, 15 g) column, 2,9,10-tribromo-1,4-dihydroanthracene-1,4-diol (27) was recrystallized from methylene chloride/hexane (20:5 mL), yield 276 mg (69%). The reaction was repeated with two

The role of silver additives in gold-mediated C–H functionalisation

• Scott R. Patrick,
• Ine I. F. Boogaerts,
• Sylvain Gaillard,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2011, 7, 892–896, doi:10.3762/bjoc.7.102

• factors must also be considered to rationalise the anomalous activity of AgI. The Lewis acidity of the silver salts may contribute to initiate the reaction [22], but unsuccessful reactions using Al2O3, AlCl3, Cu2O or ZnBr2 proved otherwise. The existence of a transient anion exchange between the gold (AuX

Continuous flow hydrogenation using polysilane-supported palladium/alumina hybrid catalysts

• Hidekazu Oyamada,
• Takeshi Naito and
• Shū Kobayashi

Beilstein J. Org. Chem. 2011, 7, 735–739, doi:10.3762/bjoc.7.83

• palladium/alumina (Pd/(PSi–Al2O3)) hybrid catalysts were developed. Our original Pd/(PSi–Al2O3) catalysts were used successfully in these systems and the hydrogenation of unsaturated C–C bonds and a nitro group, deprotection of a carbobenzyloxy (Cbz) group, and a dehalogenation reaction proceeded smoothly

• swell in any solvent, and were predicted to be applicable to continuous flow reactors. In this study, we investigated hydrogenation reactions of C–C double and triple bonds as well as various other functional groups using continuous flow systems with Pd/(PSi–Al2O3) catalysts. A schematic diagram of the

• continuous flow reactor and an image of the top of the column are shown in Figure 1. A high performance liquid chromatography (HPLC) pump was used to feed the substrate into the central hole in the top of the column, which was filled with the Pd/(PSi–Al2O3) catalyst. Hydrogen gas was introduced into the six

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

• (Scheme 37). Also, a condensation reaction between ethylenediamine and acetic acid catalysed by γ-Al2O3 at high temperatures gives 2-methylimidazole (187) in approximately 90% yield [56]. Elz and Heil [57] prepared the 1,2,3,9-tetrahydro-4H-carbazol-4-one (140) by the reaction of phenylhydrazine (138

Michael-type addition of azoles of broad-scale acidity to methyl acrylate

• Sławomir Boncel,
• Kinga Saletra,
• Barbara Hefczyc and
• Krzysztof Z. Walczak

Beilstein J. Org. Chem. 2011, 7, 173–178, doi:10.3762/bjoc.7.24

• protocol and a simple work-up. In the Michael-type additions of azole N–H acids, numerous catalysts such as KF/Al2O3 [8], CeCl3∙7 H2O/NaI [9], NaH or ZnCl2 [10], K2CO3 [11], anhydrous K3PO4 [12], (NH4)2Ce(NO3)6 (CAN) [22] or ionic liquids, e.g., Cu(acac)2 immobilised in [bmim][BF4] [15] have been used

Stereoselectivity of supported alkene metathesis catalysts: a goal and a tool to characterize active sites

• Christophe Copéret

Beilstein J. Org. Chem. 2011, 7, 13–21, doi:10.3762/bjoc.7.3

• conversions as low as 2% (vs ca. 30% thermodynamic plateau). For MeReO3/Al2O3, where the active sites is [AlSCH2ReO3] (Scheme 3a) [35][36], decreasing the conversion to well below 0.1% allows the measurement of a kinetic (E/Z) ratio of 0.4 thus showing that this catalyst is slightly Z-selective (70

• was also obtained for Re2O7/Al2O3 [40][41], which infers similar structural features for the active sites [42]. Finally, this shows that modifying the surface adsorption properties can favour the formation of primary products by slowing down secondary processes such as isomerisation, but that

Aromatic and heterocyclic perfluoroalkyl sulfides. Methods of preparation

• Vladimir N. Boiko

Beilstein J. Org. Chem. 2010, 6, 880–921, doi:10.3762/bjoc.6.88

• , Clark et al. have used CuSCF3 adsorbed onto Al2O3 [100], whilst Munavalli et al. have employed the acetonitrile adduct CF3SCu·CH3CN [103] for the reaction with m-iodobenzoic acid and its methyl ester [104]. Bulky perfluoroalkylthiocopper reagents, derived from 2,2,4,4-tetrakis(CF3)-1,3-dithietane

Solvent-free and time-efficient Suzuki–Miyaura reaction in a ball mill: the solid reagent system KF–Al₂O₃ under inspection

• Franziska Bernhardt,
• Ronald Trotzki,
• Tony Szuppa,
• Achim Stolle and
• Bernd Ondruschka

Beilstein J. Org. Chem. 2010, 6, No. 7, doi:10.3762/bjoc.6.7

• the above mentioned parameters on the results of coupling reactions. The results from ball milling experiments led to the conclusion that self-prepared and commercially available KF–Al2O3 differ in water content. The higher the residual water content, the higher are the product yields. Keywords: ball

• milling; C–C coupling; KF–Al2O3; palladium; solid reagent system; Introduction Over the last two decades, a major trend in the field of organic chemistry has been evident: environmentally friendly processes using safer reagents, generating fewer side products and requiring less use of solvents are in

• vogue [1][2]. This trend has led to an explosive growth in the fields of solvent-free synthesis [3][4][5][6][7][8][9][10][11][12][13] and solid-supported reagents [14][15][16][17][18] such as potassium fluoride on alumina (KF–Al2O3) [19][20]. This versatile reagent was originally introduced in 1979 by

Asymmetric reactions in continuous flow

• Xiao Yin Mak,
• Paola Laurino and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2009, 5, No. 19, doi:10.3762/bjoc.5.19

• was reduced using a cinchonidine-modified Pt/Al2O3 catalyst in a fixed bed reactor in both supercritical carbon dioxide and ethane [47]. Poliakoff and co-workers have investigated the continuous asymmetric hydrogenation of dimethyl itaconate in scCO2 [48][49]. By using the catalyst [Rh(COD)2(nbd

Hydrogenation of aromatic ketones, aldehydes, and epoxides with hydrogen and Pd(0)EnCat™ 30NP

• Steven V. Ley,
• Angus J. P. Stewart-Liddon,
• David Pears,
• Remedios H. Perni and
• Kevin Treacher

Beilstein J. Org. Chem. 2006, 2, No. 15, doi:10.1186/1860-5397-2-15

• -methoxyacetophenone are summarized in Table 1. In the first case, when Pd/C was used the over-reduced product was quantitatively obtained (entries 7 and 8). Using palladium on different supports with lower surface area than carbon, such as CaCO3 or Al2O3 (entries 4 and 5) a mixture of benzylic alcohol and over

• or Pd/Al2O3. Pd(0)EnCat™ 30NP-catalyzed hydrogenation of 4-mathoxybenzaldehyde and 4-methoxyacetophenone. Comparison with other Pd catalysts. Pd(0)EnCat™30NP-catalyzed hydrogenation of aryl ketones and aldehydes. Pd(0)EnCat™ 30NP-Catalyzed Hydrogenolysis of trans-stilbene oxide. Comparison with other