Nanoreactors for green catalysis

• M. Teresa De Martino,
• Loai K. E. A. Abdelmohsen,
• Floris P. J. T. Rutjes and
• Jan C. M. van Hest

Beilstein J. Org. Chem. 2018, 14, 716–733, doi:10.3762/bjoc.14.61

• (enzymes), organocatalysts and metal catalysts [47]. Catalysis is defined as heterogeneous when catalysts are in an aggregated state, and are thus in a different phase than the reactants [27][48]. Heterogeneous catalysts typically consist of a solid carrier, the so called “support”, on which catalytic

• sites are dispersed [49][50]. Homogeneous catalysis is generally performed under milder operative conditions than heterogeneous catalysis [51]. In fact, heterogeneous catalysts generally possess very high decomposition temperatures (above 100 °C) [52]. The presence of a solid phase often results in the

Heterogeneous Pd catalysts as emulsifiers in Pickering emulsions for integrated multistep synthesis in flow chemistry

• Katharina Hiebler,
• Georg J. Lichtenegger,
• Manuel C. Maier,
• Eun Sung Park,
• Renie Gonzales-Groom,
• Bernard P. Binks and
• Heidrun Gruber-Woelfler

Beilstein J. Org. Chem. 2018, 14, 648–658, doi:10.3762/bjoc.14.52

• of the catalytic active compounds. To assess the reusability of the heterogeneous catalysts, the Pd-substituted metal oxides were subjected to Suzuki–Miyaura couplings of 4-bromotoluene with phenylboronic acid in five subsequent reactions, i.e., after one reaction was finished, the particles were

• potential as heterogeneous catalysts for the synthesis of APIs, such as 1 and 2. Suzuki–Miyaura reactions in continuous flow After the applicability and versatility of the palladium substituted cerium tin oxides was confirmed in batch, the aim was to implement the catalysts in a continuous flow setup, which

An alternative to hydrogenation processes. Electrocatalytic hydrogenation of benzophenone

• Cristina Mozo Mulero,
• Alfonso Sáez,
• Jesús Iniesta and
• Vicente Montiel

Beilstein J. Org. Chem. 2018, 14, 537–546, doi:10.3762/bjoc.14.40

• K) and high-pressure (even 350 atm). Even though the hydrogenation is performed using either homogeneous or heterogeneous catalysts to enhance chemical kinetics, a number of side reactions reduces the selectivity of the chemical reaction providing also complex and cost-ineffective work-up procedures

Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides

• Irwan Iskandar Roslan,
• Kian-Hong Ng,
• Gaik-Khuan Chuah and
• Stephan Jaenicke

Beilstein J. Org. Chem. 2017, 13, 2739–2750, doi:10.3762/bjoc.13.270

• -Diels–Alder reaction [87]. Coupling between alkynoic acid and 2-aminobenzothiazole and the use of ionic liquids have also been developed [88]. Heterogeneous catalysts such as kaolin and hydrotalcites have been employed in the synthesis of benzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones [89][90

Novel approach to hydroxy-group-containing porous organic polymers from bisphenol A

• Tao Wang,
• Yan-Chao Zhao,
• Li-Min Zhang,
• Yi Cui,
• Chang-Shan Zhang and
• Bao-Hang Han

Beilstein J. Org. Chem. 2017, 13, 2131–2137, doi:10.3762/bjoc.13.211

• potential as heterogeneous catalysts [5][6][7], supports for catalysts [8][9], gas permeable membranes [10][11], and gas storage materials [12][13][14] have attracted much attentions from researchers all over the world as reviewed by Matyjaszewski [15]. During the past years, a large amount of porous

New bio-nanocomposites based on iron oxides and polysaccharides applied to oxidation and alkylation reactions

• Daily Rodríguez-Padrón,
• Alina M. Balu,
• Antonio A. Romero and
• Rafael Luque

Beilstein J. Org. Chem. 2017, 13, 1982–1993, doi:10.3762/bjoc.13.194

• has played a crucial role in the development of the chemical industry. It has allowed the design of more efficient processes, both in an economical and environmental way, thanks to the higher activity and selectivity of heterogeneous catalysts [1][2][3]. These systems, in particular, are preferred

• oxidants with heterogeneous catalysts such as Fe2O3 nanoparticles, Ag nanoparticles supported on hydrotalcites, Au nanoparticles supported on metal oxides, and Pd nanoparticles supported on SBA-15 has been developed [41][42][43][44]. In this regard, both unsupported “free” iron oxide nanoparticles [45] and

• toluene, respectively) could find current application in the valorization of lignocellulosic biomass with heterogeneous catalysis. However, the use of heterogeneous catalysts in the aforementioned reactions usually requires a filtration or centrifugation step to recover the catalyst. In order to simplify

Continuous-flow processes for the catalytic partial hydrogenation reaction of alkynes

• Carmen Moreno-Marrodan,
• Francesca Liguori and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2017, 13, 734–754, doi:10.3762/bjoc.13.73

• potential benefits of one catalytic system over the others. Review The issue of selectivity A major challenge in alkynes partial hydrogenation is to achieve 100% selectivity to the desired product at the highest conversion level [42][43]. The conventional heterogeneous catalysts often show selectivity

• substrate. Several approaches were developed to enhance the selectivity of the batch hydrogenation processes, including tuning of the reaction conditions, use of less conventional metals [58][59], alloys [60][61] or oxide active phases [62] and engineering of single-site heterogeneous catalysts [63][64]. A

• studied process, mainly because the alkene product (3a) is an important intermediate for the industrial synthesis of vitamins (A, E), as well as a variety perfumes [127][128]. The current manufacturing process is based on the Lindlar or other Pd-based heterogeneous catalysts under batch conditions. Yields

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis

• Flavio Fanelli,
• Giovanna Parisi,
• Leonardo Degennaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2017, 13, 520–542, doi:10.3762/bjoc.13.51

• isolation of intermediates, separation of the catalyst or other work-up procedures can be considered sustainable [91]. The syntheses of (S)-rolipram and a γ-aminobutyric acid (GABA) derivative were accomplished. Readily available starting materials and columns containing chiral heterogeneous catalysts to

Continuous N-alkylation reactions of amino alcohols using γ-Al₂O₃ and supercritical CO₂: unexpected formation of cyclic ureas and urethanes by reaction with CO₂

• Emilia S. Streng,
• Darren S. Lee,
• Michael W. George and
• Martyn Poliakoff

Beilstein J. Org. Chem. 2017, 13, 329–337, doi:10.3762/bjoc.13.36

• (scCO2) have mainly been focused on continuous flow systems and the etherification of alcohols, where alcohols are activated by heterogeneous catalysts [31][32][33][34][35][36][37][38]. We have usually employed γ-alumina as the catalyst, as this is a simple, readily available and environmentally benign

Selective synthesis of thioethers in the presence of a transition-metal-free solid Lewis acid

• Federica Santoro,
• Matteo Mariani,
• Federica Zaccheria,
• Rinaldo Psaro and
• Nicoletta Ravasio

Beilstein J. Org. Chem. 2016, 12, 2627–2635, doi:10.3762/bjoc.12.259

• consequent waste reduction can be recognized as important factors for environmental protection. In this context organic synthesis over heterogeneous catalysts instead of homogeneous ones or without employing any organic solvents is of paramount interest [1][2]. In particular, metal-free coupling reactions

Diels–Alder reactions in confined spaces: the influence of catalyst structure and the nature of active sites for the retro-Diels–Alder reaction

• Ángel Cantín,
• M. Victoria Gomez and
• Antonio de la Hoz

Beilstein J. Org. Chem. 2016, 12, 2181–2188, doi:10.3762/bjoc.12.208

• selectivity and atom economy. Moreover, Diels–Alder cycloadditions in combination with heterogeneous catalysts (i.e. doped-microporous materials) represent an interesting approach for the conversion of biomass feedstock into stable chemicals such as furfural derivatives, platform molecules which can be

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

• , their steric hindrance quenches any reactivity. Conclusion Silica-supported sulfonic acids proved very active heterogeneous catalysts for the selective esterification of levulinic acid with stoichiometric amounts of primary alcohols. The esterification can be carried out under mild conditions (75 °C, 2

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

• popular catalytic systems [3]. These include both acids such as sulfuric, sulfonic, phosphoric, and hydrochloric, and bases such as metal alkoxides, acetates, oxides, and carbonates. It is worth mentioning, that transesterification reactions are frequently carried out over solid (heterogeneous) catalysts

• an elegant investigation on the model transesterification of ethyl acetate with methanol [9]. The production of biodiesel blends is another sector in which the catalytic transesterification is extensively used. In particular, heterogeneous catalysts including calcium, manganese and zinc oxides as

• uses in place of the common homogeneous or heterogeneous catalysts for the transesterification of natural triglycerides in the production of biodiesel. A recent example has reported that a methylimidazolium salt with an alkyl chain mimicking the glycerol structure, promotes the almost quantitative

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• in the Baeyer–Villiger reaction with increasing frequency. Various catalysts that activate hydrogen peroxide, such as heterogeneous catalysts based on solid acids [201], zeolites [202][203], Se [204], As [205], Co [206], sulfonated organic ion exchange resins [203][207], and homogeneous catalysts

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• H2SO4 or Lewis acids such as SnCl2, FeCl3 and VCl3, as well as heterogeneous catalysts including silica gel supported sulfuric acid and sodium hydrogen sulfate did not affect this reaction. Also, the reaction in the presence of p-toluenesulfonic acid (TsOH), in aprotic solvents proceeded with much

Superstructures with cyclodextrins: chemistry and applications III

• Gerhard Wenz and
• Eric Monflier

Beilstein J. Org. Chem. 2016, 12, 937–938, doi:10.3762/bjoc.12.91

• of highly active heterogeneous catalysts. Accordingly, the catalytic transformation of bio-oil has been achieved over Cu/MCM-41 and Cu/Kit-6 catalysts obtained by a CD assisted co-impregnation method [12]. Furthermore, the combination of template-directed colloidal self-assembly with a CD-assisted

Enabling technologies and green processes in cyclodextrin chemistry

• Giancarlo Cravotto,
• Marina Caporaso,
• Laszlo Jicsinszky and
• Katia Martina

Beilstein J. Org. Chem. 2016, 12, 278–294, doi:10.3762/bjoc.12.30

• sources been tested for their ability to activate C–C and C–X bond formation. In recent years non-conventional energy sources, such as microwaves (MW), ultrasound (US), ball mills (BM) and microreactors have made access to CD derivatives much simpler, as have heterogeneous catalysts and greener solvents

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

• ruthenium [19][20][21][22][23][24]. In other contributions originating from the same group, heterogeneous catalysts covalently connected to a monolithic support via NHC ligands were presented [25][26]. These initiators were suitable for continuous metathesis processes and provided products with low residual

Reactions of nitroxides 15. Cinnamates bearing a nitroxyl moiety synthesized using a Mizoroki–Heck cross-coupling reaction

• Jerzy Zakrzewski and
• Bogumiła Huras

Beilstein J. Org. Chem. 2015, 11, 1155–1162, doi:10.3762/bjoc.11.130

• a heterogeneous catalyst which is immobilized on a solid support. In addition to the widely highlighted unquestionable advantages of immobilized, heterogeneous catalysts (easy separation from the reaction mixture and the possibility of re-use), such catalysts are rigidly anchored on a carrier and

CO₂ Chemistry

• Thomas E. Müller and
• Walter Leitner

Beilstein J. Org. Chem. 2015, 11, 675–677, doi:10.3762/bjoc.11.76

• highly reactive molecules that are isoelectronic to carbon dioxide. Threefold reactivity of carbon dioxide and examples for different activation modes for CO2 involving metal centres in homogeneous and heterogeneous catalysts [5][6].

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

• with low-molecular-weight alcohols was performed in the presence of heterogeneous catalysts, such as Au/TiO2 [98][99][100], Au/β-Ga2O3 [101], Au/polymer [102], and AuNiOx/SiO2-Al2O3-MgO [103]. In all the above-mentioned processes in the presence of heterogeneous catalysts, low-molecular-weight alcohols

• ]. The coupling of aldehydes and formamides with 2-substituted phenols was carried out in the presence of heterogeneous catalysts, such as CuO on α-Fe2O3-modified carbon nanotubes (a magnetically separable catalyst) [158] and the metal-organic framework Cu2(4,4’-biphenyldicarboxylate)2(4,4’-bipyridine

Anion effect controlling the selectivity in the zinc-catalysed copolymerisation of CO₂ and cyclohexene oxide

• Sait Elmas,
• Muhammad Afzal Subhani,
• Walter Leitner and
• Thomas E. Müller

Beilstein J. Org. Chem. 2015, 11, 42–49, doi:10.3762/bjoc.11.7

• heterogeneous catalysts are known to catalyse the copolymerisation reaction [5][11][12][13]. One lead structure (Scheme 1) for catalysing the reaction is based on binuclear complexes with a macrocyclic ligand framework (Type I) [14][15][16]. The macrocyclic ligand L is a 22-membered Robson-type ligand with four

Pd/C-catalyzed aerobic oxidative esterification of alcohols and aldehydes: a highly efficient microwave-assisted green protocol

• Marina Caporaso,
• Giancarlo Cravotto,
• Spyros Georgakopoulos,
• George Heropoulos,
• Katia Martina and
• Silvia Tagliapietra

Beilstein J. Org. Chem. 2014, 10, 1454–1461, doi:10.3762/bjoc.10.149

• Selective oxidations of alcohols are some of the most important transformations in organic synthesis. Therefore, reactions that employ reusable heterogeneous catalysts and molecular oxygen are highly desirable from atom economy and environmental impact point of view [1][2][3]. A number of methods have been

Integration of enabling methods for the automated flow preparation of piperazine-2-carboxamide

• Richard J. Ingham,
• Claudio Battilocchio,
• Joel M. Hawkins and
• Steven V. Ley

Beilstein J. Org. Chem. 2014, 10, 641–652, doi:10.3762/bjoc.10.56

• pyrazine 2 to piperazine 1 (Figure 2b). Both of these steps involve flowing through heterogeneous catalysts, a metal oxide for the hydration of the nitrile and a supported precious metal for the hydrogenation of the heteroaromatic ring. Furthermore, both steps involve the addition of a volatile small

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

• [Au(III)salen] [20] and [Au(III)(2-phenylpyridine)Cl2] [21] complexes, immobilized heterogeneous catalysts [22], and gold nanoparticles (Au NP) [23][24][25][26] have been reported until 2010, as well as recognized in two recent exhaustive reviews by Li [2] and Van der Eycken [3]. In the past three

• years the development of new and effective nanostructured catalytic systems dominated the gold-catalyzed approach to A3-coupling. For example, ultrasmall gold(0) nanoparticles embedded in a mesoporous carbon nitride stabilizer [27] proved to be a highly active, selective and recyclable heterogeneous

• catalysts for coupling arylaldehydes, piperidine and phenylacetylene in toluene at 100 °C. One year later, the same research group obtained comparable results under identical reaction conditions by using gold(0) nanoparticles stabilized by nanocristalline magnesium oxide [28]. In this work, the scope was