Silica-supported sulfonic acids as recyclable catalyst for esterification of levulinic acid with stoichiometric amounts of alcohols

• Raimondo Maggi,
• N. Raveendran Shiju,
• Veronica Santacroce,
• Giovanni Maestri,
• Franca Bigi and
• Gadi Rothenberg

Beilstein J. Org. Chem. 2016, 12, 2173–2180, doi:10.3762/bjoc.12.207

• performing a filtration test. In agreement with the hypothesis, we monitored no further conversion on the filtrate [41], proving that no leaching occurred. The recyclability of the catalyst was then evaluated. The catalyst was recovered by filtration, washed with ethyl acetate (10 mL), dried and reused for a

Ionic liquids as transesterification catalysts: applications for the synthesis of linear and cyclic organic carbonates

• Maurizio Selva,
• Alvise Perosa,
• Sandro Guidi and
• Lisa Cattelan

Beilstein J. Org. Chem. 2016, 12, 1911–1924, doi:10.3762/bjoc.12.181

• inorganic or solid acids and bases. Advantages in this case are mainly the recovery and recyclability of the catalyst system and the improved selectivity that is often achievable. Secondly, the here presented reactions have a common mechanistic feature based on the cooperative nucleophilic–electrophilic

Supported bifunctional thioureas as recoverable and reusable catalysts for enantioselective nitro-Michael reactions

• José M. Andrés,
• Miriam Ceballos,
• Alicia Maestro,
• Isabel Sanz and
• Rafael Pedrosa

Beilstein J. Org. Chem. 2016, 12, 628–635, doi:10.3762/bjoc.12.61

• with chiral bifunctional thioureas looking for a greener process [28], easier recovering and recyclability of the catalyst, and solvent-free reaction conditions. Along these lines, we have recently reported the bottom-up synthesis of polymeric thioureas [29], and the anchorage of (L)-valine-derived

• ) reacted very well with 1a, leading to 5ae in excellent yield and enantioselectivity, but only moderate diastereoselectivity (dr 70:30, Table 3, entry 10). To test the recyclability of catalyst V we choose the reaction of 1a with 3a in neat conditions and 5 mol % of catalyst as model. Once the reaction had

• . The anti- and syn-isomers of the Michael products were not separated by column chromatography. The diastereomeric ratio was determined by 1H NMR spectroscopy of the purified product. Recyclability of the supported thiourea catalysts in nitro-Michael reaction. The supported catalysts were recovered

Effective immobilisation of a metathesis catalyst bearing an ammonium-tagged NHC ligand on various solid supports

• Krzysztof Skowerski,
• Jacek Białecki,
• Stefan J. Czarnocki,
• Karolina Żukowska and
• Karol Grela

Beilstein J. Org. Chem. 2016, 12, 5–15, doi:10.3762/bjoc.12.2

• strategies, rather than tackling recyclability issues. The latter was studied in a separate project conducted in our laboratories and recently published [49]. In that parallel study the NHC ammonium-tagged catalyst was heterogenised and subjected to various recyclability tests, proving high potential (up to

• , such as water, alcohol or CH2Cl2 (Figure 9D and Figure 9E) and possibly deposited on other supports or used as a homogeneous catalyst. As it was noted earlier, we are not considering high recyclability of immobilised complex 8. However, the possibility of removing the deactivated catalyst from the

• resulted system. In parallel work, the recyclability of an immobilised Ru-catalyst bearing quaternary ammonium-tagged NHC ligand was described. Selected classical and heterogeneous ruthenium complexes. Applications of NHC ammonium-tagged catalysts. Influence of temperature and concentration on RCM of 9

Olefin metathesis in air

• Lorenzo Piola,
• Fady Nahra and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 2038–2056, doi:10.3762/bjoc.11.221

• retained the properties of stability and recyclability. In 2002, Hoveyda et al. reported the Hoveyda–Grubbs’ 2nd generation type catalyst 36 (Figure 3) [56]: Complex 36, bearing an unsymmetrical and chiral NHC, was active in the asymmetric ring-opening cross-metathesis (RO/CM) in air using undistilled

• afforded average to high yields under air (Table 2). Reactions were performed in water at rt. Catalyst 69 was the most soluble in water; however, it did not afford the highest catalytic activity. In order to test the recyclability of the complex, diethyl diallymalonate (29) was subjected to RCM reaction in

Rasta resin–triphenylphosphine oxides and their use as recyclable heterogeneous reagent precursors in halogenation reactions

• Xuanshu Xia and
• Patrick H. Toy

Beilstein J. Org. Chem. 2014, 10, 1397–1405, doi:10.3762/bjoc.10.143

• , and realizing that it was returned as the byproduct of the above reactions, we next examined its recyclability in the chlorination of alcohol 4H and aziridine 8B. The results of these studies are shown in Table 4 and Table 5, respectively. In these experiments, the polymer recovered by filtration of

• and 4), and alkyl substutients (Table 6, entries 5–8) all proceeded to completion, and afforded the corresponding 1,2-dihalides in excellent yields. We also examined the recyclability of 18 in the halogenation of epoxide 10C (Table 7). As was the case for 16, bifunctional polymer 18 could be

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• reactions of activated organic electrophiles [2][3][4][5][6][7][8]. Despite the numerous examples of efficient catalytic photoredox transformations with organometallic dyes known to date, their high price, toxicity profile, and problematic recyclability might limit their more general use especially on

Nonanebis(peroxoic acid): a stable peracid for oxidative bromination of aminoanthracene-9,10-dione

• Vilas Venunath Patil and
• Ganapati Subray Shankarling

Beilstein J. Org. Chem. 2014, 10, 921–928, doi:10.3762/bjoc.10.90

• dibrominated product along with good recyclability of the solvent. The present work is an extension of our previous work (Scheme 1). Here, we report the use of nonanebis(peroxoic acid) as an oxidant for bromination of aminoanthracene-9,10-dione. To the best of our knowledge, use of this stable, solid peroxy

Silica sulfuric acid: a reusable solid catalyst for one pot synthesis of densely substituted pyrrole-fused isocoumarins under solvent-free conditions

• Sudipta Pathak,
• Kamalesh Debnath and
• Animesh Pramanik

Beilstein J. Org. Chem. 2013, 9, 2344–2353, doi:10.3762/bjoc.9.269

• reactions in solution because of simple work-up procedures, improved product yields, greater ease of purification, shorter reaction times, milder reaction conditions, and recyclability of the catalyst [24]. In the recent years, silica sulfuric acid (SSA) has shown immense potentiality as an efficient and

• easily retrievable solid catalyst in various important organic syntheses under solvent-free conditions [25]. The high catalytic activity, the operational simplicity and the recyclability of SSA can be exploited in the industry for the synthesis of various drugs and pharmaceuticals. SSA, a product that is

Flow synthesis of phenylserine using threonine aldolase immobilized on Eupergit support

• Jagdish D. Tibhe,
• Hui Fu,
• Timothy Noël,
• Qi Wang,
• Jan Meuldijk and
• Volker Hessel

Beilstein J. Org. Chem. 2013, 9, 2168–2179, doi:10.3762/bjoc.9.254

• difficulty of enzyme recovery. Recently, Wang et al. have shown that the activity and recyclability of the CalB enzyme can be enhanced by the use of a polymersome Pickering emulsion. As such, a biphasic system could be used by loading the enzyme in the aqueous phase and organic reagents in the polymersome [3

Practical synthesis of indoles and benzofurans in water using a heterogeneous bimetallic catalyst

• Cybille Rossy,
• Eric Fouquet and
• François-Xavier Felpin

Beilstein J. Org. Chem. 2013, 9, 1426–1431, doi:10.3762/bjoc.9.160

• [36][37]. Finally, the recyclability of our homemade Pd–Cu/C catalyst was evaluated for the preparation of indole 4. Unfortunately, we found that the yield dramatically decreases to 60% (compared to 90% with the fresh catalyst) after the second run and the catalyst was inactive after the third run

Diastereoselective synthesis of nitroso acetals from (S,E)-γ-aminated nitroalkenes via multicomponent [4 + 2]/[3 + 2] cycloadditions promoted by LiCl or LiClO₄

• Leandro Lara de Carvalho,
• Robert Alan Burrow and
• Vera Lúcia Patrocinio Pereira

Beilstein J. Org. Chem. 2013, 9, 838–845, doi:10.3762/bjoc.9.96

• reaction promoter. These salts were chosen in particular because of their present high recyclability, low cost, and great applicability as promoters in cycloaddition processes [12][13][14][15][16][17]. Thus, the reactions between the very reactive beta-nitrostyrene 5d, used as a model compound, and the

Iron-containing mesoporous aluminosilicate catalyzed direct alkenylation of phenols: Facile synthesis of 1,1-diarylalkenes

• Satyajit Haldar and
• Subratanath Koner

Beilstein J. Org. Chem. 2013, 9, 49–55, doi:10.3762/bjoc.9.6

• advantageous aspect of this type of solid-support catalyst is their scope for recycling. The reaction between phenol and phenylacetylene under optimized conditions was chosen to evaluate the recyclability of Fe-Al-MCM-41. The catalyst was separated after the completion of the reaction by simple centrifugation

Ion-exchange-resin-catalyzed adamantylation of phenol derivatives with adamantanols: Developing a clean process for synthesis of 2-(1-adamantyl)-4-bromophenol, a key intermediate of adapalene

• Nan Wang,
• Ronghua Wang,
• Xia Shi and
• Gang Zou

Beilstein J. Org. Chem. 2012, 8, 227–233, doi:10.3762/bjoc.8.23

• first use. Therefore, both the resin catalyst and the acetic acid solvent can be easily recovered by simple filtration and readily reused. The recyclability of the acidic ion-exchange-resin catalyst was then investigated (Figure 1). To facilitate the operation, the reaction was run at 15 mmol scale with

PEG-embedded KBr₃: A recyclable catalyst for multicomponent coupling reaction for the efficient synthesis of functionalized piperidines

• Sanny Verma,
• Suman L. Jain and
• Bir Sain

Beilstein J. Org. Chem. 2011, 7, 1334–1341, doi:10.3762/bjoc.7.157

• tetrabutylammonium tribromide (TBATB) [30], bromodimethylsulfonium bromide (BDMS) [31], InCl3 [32] and L-proline/TFA [33] were reported for the one-pot syntheses of these heterocyclic compounds. However, tedious synthetic procedures, the need for high catalyst loadings, and the expense and non-recyclability of the

Nano copper oxide catalyzed synthesis of symmetrical diaryl sulfides under ligand free conditions

• K. Harsha Vardhan Reddy,
• V. Prakash Reddy,
• A. Ashwan Kumar,
• G. Kranthi and
• Y.V.D. Nageswar

Beilstein J. Org. Chem. 2011, 7, 886–891, doi:10.3762/bjoc.7.101

• and ligands [43], long reaction times [43][44], metal contamination of the final product, and non recyclability of the catalyst. This leads to increased costs as well as limiting the scope of the reaction. From the synthetic point of view, it is desirable to find novel recyclable catalytic systems

Air-stable, recyclable, and time-efficient diphenylphosphinite cellulose-supported palladium nanoparticles as a catalyst for Suzuki–Miyaura reactions

• Qingwei Du and
• Yiqun Li

Beilstein J. Org. Chem. 2011, 7, 378–385, doi:10.3762/bjoc.7.48

• ) lattice planes of the face-centered cubic crystalline structure of the Pd nanoparticles are correspondingly clearly seen from the XRD pattern of Cell–OPPh2–Pd0 catalyst. The thermal stability of Cell–OPPh2–Pd0 has a great effect on its catalytic activity and recyclability because the Suzuki–Miyaura

C–C (alkynylation) vs C–O (ether) bond formation under Pd/C–Cu catalysis: synthesis and pharmacological evaluation of 4-alkynylthieno[2,3-d]pyrimidines

• Dhilli Rao Gorja,
• K. Shiva Kumar,
• K. Mukkanti and
• Manojit Pal

Beilstein J. Org. Chem. 2011, 7, 338–345, doi:10.3762/bjoc.7.44

• -tetrahydrobenzothieno[2,3-d]pyrimidine. The use of another palladium catalyst (PPh3)2PdCl2 was also examined and found to be effective (Table 1, entry 7). However, we preferred to use Pd/C because it is less expensive, easy to handle and separable from the product and has the potential for recyclability, for a review

• see [13]. To assess the recyclability of the recovered Pd/C-catalyst in the present coupling reaction, the reaction mixture of 1a and 2a (Table 1, entry 2) was allowed to cool to room temperature and filtered. The residue was washed with MeOH, acetone, and DCM. After drying under vacuum the recovered

• catalyst was used directly in the reaction of 1a with 2a in the presence of PPh3, CuI, and Et3N: A conversion of 85% was observed confirming the recyclability of the recovered Pd/C-catalyst. Having established the optimum reaction conditions for the preparation of 3a we decided to test the generality and

Olefin metathesis in nano-sized systems

• Didier Astruc,
• Abdou K. Diallo,
• Sylvain Gatard,
• Liyuan Liang,
• Cátia Ornelas,
• Victor Martinez,
• Denise Méry and
• Jaime Ruiz

Beilstein J. Org. Chem. 2011, 7, 94–103, doi:10.3762/bjoc.7.13

• of catalysts to dendrimers was mostly focused on the recovery of the catalyst. Only a few metallodendritic carbene complexes with covalent binding of the olefin metathesis catalyst are known. Prior to our involvement only compounds with four branches were known [11][12][13][14] but good recyclability

New library of aminosulfonyl-tagged Hoveyda–Grubbs type complexes: Synthesis, kinetic studies and activity in olefin metathesis transformations

• Etienne Borré,
• Frederic Caijo,
• Christophe Crévisy and
• Marc Mauduit

Beilstein J. Org. Chem. 2010, 6, 1159–1166, doi:10.3762/bjoc.6.132

• . [14]. Nevertheless, some difficulties remain, for instance: Lower yields are observed when successive silica gel chromatography is performed and some scavengers are very toxic (PbOAc2, DMSO…) [15]. Another strategy aims to control the catalyst activity in order to improve recyclability. Recently

• with excellent recyclability (up to 60% at 0.3 mol %). Extremely low levels of Ru-contamination in the final products were determined by ICP-MS analyses (below 6 ppm) after silica gel chromatography. Additionally, a recent study in the synthesis of natural products involving a library of precatalysts 3

Suzuki–Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported N-heterocyclic carbene–palladium complex catalyst

• Guangming Nan,
• Fang Ren and
• Meiming Luo

Beilstein J. Org. Chem. 2010, 6, No. 70, doi:10.3762/bjoc.6.70

• at different temperatures, which suggested that the reaction temperature did not apparently influence the final reaction yield (Table 3, entry 7). After optimizing the amount of catalyst, solvent, substrate ratio and temperature, the recyclability of the polymer-supported Pd–NHC catalyst for the

• demonstrate the general recyclability of the catalyst, the recovered catalysts from the first, fifth and eighth runs of the reaction of 1-(3-nitrophenyl)-2-(pyrrolidin-1-yl)diazene and phenylboronic acid were also used to catalyze the reaction of 1-phenyl-2-(pyrrolidin-1-yl)diazene and 4-methoxyphenylboronic

• still retains high activity, which reflects its high stability and recyclability. Advantages of this method also include good substrate generality, good chemoselectivity over arylhalides and mild reaction conditions. Experimental General All chemicals were obtained from commercial sources and were, in

C-Arylation reactions catalyzed by CuO-nanoparticles under ligand free conditions

• Mazaahir Kidwai,
• Saurav Bhardwaj and
• Roona Poddar

Beilstein J. Org. Chem. 2010, 6, No. 35, doi:10.3762/bjoc.6.35

• aryl halides. The products were obtained in good to excellent yield. The catalyst can be recovered and reused for four cycles with almost no loss in activity. Keywords: active methylene compounds; C-arylation; heterogeneous catalyst; recyclability; Introduction Carbon-carbon (C–C) bond formation is

Ring opening metathesis polymerization-derived block copolymers bearing chelating ligands: synthesis, metal immobilization and use in hydroformylation under micellar conditions

• Gajanan M. Pawar,
• Jochen Weckesser,
• Siegfried Blechert and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2010, 6, No. 28, doi:10.3762/bjoc.6.28

• their MS spectra as well as by their retention times using commercially available compounds as reference material. Recyclability studies with poly(M1-b-M2)-Rh: Hydroformylations were carried out as described above. For recycling, the product was extracted with diethyl ether (4 × 10 mL). Fresh 1-octene

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

• . Thus, the use of aqueous solvents in chemical reactions has proved a cleaner and safer alternative to organic solvents [2]. Heterogeneous catalysis, which has the immediate advantage of easy recoverability and recyclability of the catalyst – sometimes with the further advantage of increased selectivity

• acid with this mild procedure was 88% (3b, Table 2). The protocol described above provides an efficient method for Knoevenagel condensation between aromatic aldehydes and active methylene groups using HAP–Cs2CO3 as a new recyclable solid base catalyst in water. Moreover, the recyclability of this

• catalyst (HAP–Cs2CO3) makes the method very cost-effective. Heterogeneity and recyclability of the catalyst When using supported heterogeneous catalysts, there are two important points to consider: heterogeneity and recyclability. To rule out the possibility of homogeneous catalysis, a reaction between 4

Can we measure catalyst efficiency in asymmetric chemical reactions? A theoretical approach

• Shaimaa El-Fayyoumy,
• Matthew H. Todd and
• Christopher J. Richards

Beilstein J. Org. Chem. 2009, 5, No. 67, doi:10.3762/bjoc.5.67

• considered here will be important in explaining the adoption of a catalyst, or a particular chemical route, by industry. Cost of starting materials, and the hazards involved in a process are key considerations from a manufacturing perspective. Aqueous or air compatibility and recyclability are two features