Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

• of green chemistry. Organocatalysis is the acceleration of chemical reactions with the use of small organic compounds, which do not contain any amounts of enzyme or inorganic elements [37][38][39]. The benefits of solid acid catalysis render them as an appealing choice, compared to their liquid

• counterparts, due to their recyclability, ease of handling, and low cost [40]. Carbon-based solid acid catalysts especially are an interesting catalyst class, because they display low corrosiveness, toxicity, and higher catalytic activity, while also being insoluble in most organic solvents. The large amount

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• of acid-sensitive pyrrole derivatives without decomposition in a short time. Abid et al. [89] described the synthesis of N-substituted pyrrole derivatives in good yields using K-10 montmorillonite as an effective solid acid catalyst under microwave irradiation. K-10 monomorillonite is a widely used

• solid acid catalyst, which features strong acidity, larger surface area and high stability. Pyrrole derivatives 73 were prepared in 83–95 % yields by condensation reactions between various alkyl-, aryl-, heteroaryl-, and sulfonylamines 72 and 2,5-dimethoxytetrahydrofuran (2) under MW conditions at 100

Automated grindstone chemistry: a simple and facile way for PEG-assisted stoichiometry-controlled halogenation of phenols and anilines using N-halosuccinimides

• Dharmendra Das,
• Akhil A. Bhosle,
• Amrita Chatterjee and
• Mainak Banerjee

Beilstein J. Org. Chem. 2022, 18, 999–1008, doi:10.3762/bjoc.18.100

• requires the use of a solid acid catalyst [52], apart from the use of high-cost, high-end milling equipment which limits to laboratory scale only. Therefore, developing an operationally simple, environmentally benign protocol, potentially useful for the batch-scale synthesis of aryl halides is highly

• of the solid acid catalyst and the cost of high-end milling instruments are additional considerations for that method [52]. Conclusion In conclusion, we have developed a facile and sustainable mechanochemical route for the catalyst-free halogenation of phenol and aniline derivatives using N

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

Valorisation of plastic waste via metal-catalysed depolymerisation

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

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• which Zn ions act as Lewis acid activators for the C=O ester bonds toward nucleophilic attack by EG. In addition to soluble catalysts, metal-containing insoluble materials, namely solid acid catalysts, were developed for the glycolytic depolymerisation of PET by EG. Representative data are summarised in

A novel and robust heterogeneous Cu catalyst using modified lignosulfonate as support for the synthesis of nitrogen-containing heterocycles

• Bingbing Lai,
• Meng Ye,
• Ping Liu,
• Minghao Li,
• Rongxian Bai and
• Yanlong Gu

Beilstein J. Org. Chem. 2020, 16, 2888–2902, doi:10.3762/bjoc.16.238

• ; heterogeneous catalyst; immobilized copper catalyst; lignosulfonate; nitrogen-containing heterocycles; solid acid; Introduction Heterogeneous metal catalysts have been continuously receiving considerable attention in the field of organic synthesis owing to the advantages of easy separation and recycling [1][2

One-pot synthesis of isosorbide from cellulose or lignocellulosic biomass: a challenge?

• Isaline Bonnin,
• Raphaël Mereau,
• Thierry Tassaing and
• Karine De Oliveira Vigier

Beilstein J. Org. Chem. 2020, 16, 1713–1721, doi:10.3762/bjoc.16.143

• Solid acid catalysts such as ion exchange resins exhibiting sulfonic groups on their external surface resembling to some extent p-toluenesulfonic acid (p-TSA) can be used in combination with supported metal catalyst (Scheme 6). Yamaguchi et al. used a combination of Ru/C and Pt/C with Amberlyst 70, an

• step reported in the literature, several researchers investigated the direct conversion of cellulose or lignocellulosic biomass to isosorbide. Several strategies were employed such as a combination of homogeneous acid and supported metal catalyst, or a combination of supported metal catalyst and solid

• acid or a metal on an acid support. Here, we will report all these strategies to perform the one-pot conversion of (ligno)cellulose to isosorbide and the key parameters of this reaction (acidity, nature of the feedstocks, poisoning of the catalyst). Review Combination of an acidic homogeneous catalyst

Synthesis of the tetrasaccharide repeating unit of the O-specific polysaccharide of Azospirillum doebereinerae type strain GSF71^T using linear and one-pot iterative glycosylations

• Arin Gucchait,
• Pradip Shit and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2020, 16, 1700–1705, doi:10.3762/bjoc.16.141

• on silica (HClO4-SiO2) [31][32]. HClO4-SiO2 was used as a noncorrosive solid acid in the glycosylation reactions. The selection of functional groups and their post-glycosylation modifications led to the formation of partially O-acetylated tetrasaccharide 1, as found in the naturally isolated

• common glycosyl donor provided the desired compound in a minimum number of reaction steps. HClO4-SiO2 was used as a solid acid activator in the glycosylation reactions as well as for functional group transformation. Experimental General methods: All reactions were monitored by thin-layer chromatography

Convenient synthesis of the pentasaccharide repeating unit corresponding to the cell wall O-antigen of Escherichia albertii O4

• Tapasi Manna,
• Arin Gucchait and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2020, 16, 106–110, doi:10.3762/bjoc.16.12

• presence of HClO4/SiO2 as a solid acid activator [31] to provide tetrasaccharide derivative 11 in 76% yield, which was de-O-acetylated to furnish tetrasaccharide acceptor 14 in 94% yield. The formation of compound 11 with appropriate configuration at the glycosidic linkages was supported by its NMR

• pentasaccharide repeating unit of the cell wall O-antigen of Escherichia albertii O4 in very good yield. Although the target compound can be achieved by block synthetic approach but a better yield of the product was obtained by a sequential approach. HClO4/SiO2 was used as a solid acid activator in the

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• trimethylsilylated phenyl-modified SBA-15 78. This white solid was reacted with ClSO3H to get SBA-15 functionalized with phenyl sulfonic acid groups (SBA-15-Ph-SO3H, 79, Scheme 14). The SBA-15-Ph-SO3H catalyst 79 is a hydrophobic nanoreactor solid acid catalyst that presents a series of advantages, such as

• -functionalized catalyst. The SBA-15-SO3H containing fluorinated alcohols had more catalytic activity [60]. In an initiative research, Doustkhah and Rostamnia developed a green catalytic system based on SBA-15 mesoporous silica with sulfamic acid content. This heterogeneous Brønsted solid acid was used as an

• intermediate IV. Finally, this intermediate is split by a nucleophilic attack of hydroxyl radicals to afford byproducts (including acetic acid, acetanilide, and formic acid) and desired product. The proposed mechanism was confirmed by EPR spectrum. The SSA catalyst is an inexpensive and reusable solid acid

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• pentoxide (P2O5) [46], silica-supported phosphorus pentoxide (P2O5-SiO2) [47], N,N,N’,N’-tetrabromobenzene-1,3-disulfonamide (TBBDA) [48], 1-methyl-3-(2-(sulfoxy)ethyl)-1H-imidazol-3-ium chloride (MSI) [49], succinic acid [50], tannic acid [49], p-nitrobenzoic acid [52], a carbon-based solid acid (CBSA) [53

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

• . The quantity of probe molecule adsorbed by the solid acid catalyst can subsequently be easily quantified. In order to distinguish between Lewis and Brønsted acidity, it was assumed that all DMPY selectively titrates Brønsted sites (methyl groups hinder coordination of nitrogen atoms with Lewis acid

Sustainable synthesis of 3-substituted phthalides via a catalytic one-pot cascade strategy from 2-formylbenzoic acid with β-keto acids in glycerol

• Lina Jia and
• Fuzhong Han

Beilstein J. Org. Chem. 2017, 13, 1425–1429, doi:10.3762/bjoc.13.139

• /cyclization reaction of 2-formylbenzoic acid and substituted ketones catalyzed by strong acids [15][16][17], strong bases [18][19] and solid acid catalysts [20][21]. The majority of these protocols generally suffer from one or more drawbacks, such as the requirement of stoichiometric or excess amounts of

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

• Federica Santoro Matteo Mariani Federica Zaccheria Rinaldo Psaro Nicoletta Ravasio CNR ISTM, via C. Golgi 19, 20133 Milano, Italy 10.3762/bjoc.12.259 Abstract The synthesis of thioethers starting from alcohols and thiols in the presence of amorphous solid acid catalysts is reported. A silica

• thiols and benzylic alcohols under solvent-free conditions in excellent yields [21]. We already reported on the use of amorphous solid acid catalysts in organic synthesis. These solids are formed by dispersing a small amount of an inorganic oxide with Lewis acid nature onto the surface of silica [22]. In

• wide as other systems only convert propargylic alcohols [30] or benzhydrol and electron-deficient thiols [31] in agreement with the high electrophilicity of these substrates. Conclusion Amorphous solid acid catalysts are very promising materials in the roadmap to green and sustainable organic synthesis

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

• context, levulinic acid, which is easily obtained from cellulose, is valuable since it can be transformed into a variety of industrially relevant fine chemicals. Here we present a simple protocol for the selective esterification of levulinic acid using solid acid catalysts. Silica supported sulfonic acid

• particular, issues with catalyst recycling and product separation limits the environmental viability of this strategy. As a result, it remains of high interest to develop alternatives to trigger this reaction, which are more sustainable, for instance through the design of suitable and recyclable solid acid

Continuous flow nitration in miniaturized devices

• Amol A. Kulkarni

Beilstein J. Org. Chem. 2014, 10, 405–424, doi:10.3762/bjoc.10.38

• be overlooked without focusing entirely on using the “micro reactor” concept. 3.1.4 Nitration with solid acid catalysts. The continuous flow vapour phase nitration using a solid acid catalyst has also been explored [26]. It is known that the solid acid catalysts, i.e., ZSM and other zeolite catalysts

• , can improve the selectivity of p-nitrotoluene in a conventional reactor using a mixed acid as the nitrating agent [52][53]. Continuous flow nitration of toluene in a packed bed microreactor using concentrated nitric acid as the nitrating agent was reported by Halder et al. [54]. Different ‘solid acid

• microreactor, concentrated nitric acid reacted very rapidly in the absence of any sulfuric acid or a solid acid catalyst. Nitric acid and toluene were brought into contact by using a SS316L T-mixer (1.58 mm inner diameter) at room temperature. The immiscible reactants were passed through a tubular microreactor

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

• temperature was lower and the yields of the products were higher, the yields were still only moderate. This encouraged us to execute the optimization study in presence of a solid acid catalyst under solvent-free conditions. This is one important facet of green chemistry: the eradication of solvents in

• reaction mixture to 100 °C (Table 1, entries 9 and 10). Unfortunately, the reactions on silica gel and MSA failed to give the desired product 8a. In the search of a suitable solid acid catalyst we employed silica sulfuric acid (SSA) at 100 °C. However, the reaction mixture got charred after 0.5 h and a

Camera-enabled techniques for organic synthesis

• Steven V. Ley,
• Richard J. Ingham,
• Matthew O’Brien and
• Duncan L. Browne

Beilstein J. Org. Chem. 2013, 9, 1051–1072, doi:10.3762/bjoc.9.118

• setup that might not otherwise be available. Suzuki–Miyaura reaction performed within a microfluidic system. The product is observed by high-speed microscope photography, which shows a precipitate forming within the microdroplets. Friedel–Crafts reactions performed by using solid-acid catalysis at high

Perhydroazulene-based liquid-crystalline materials with smectic phases

• Zakir Hussain,
• Henning Hopf and
• S. Holger Eichhorn

Beilstein J. Org. Chem. 2012, 8, 403–410, doi:10.3762/bjoc.8.44

• impurities with dichloromethane and finally washing the column with Et2O to yield 240 mg (87%) of 6a as a colorless solid. Acid 6b was obtained from ester 5b by the same procedure as for 6a in 84% yield (230 mg), also as a colorless solid. Compound 6a: Mp 102–104 °C; 1H NMR (400.1 MHz, CDCl3) δ 0.85 (t, 3J

Continuous-flow hydration–condensation reaction: Synthesis of α,β-unsaturated ketones from alkynes and aldehydes by using a heterogeneous solid acid catalyst

• Magnus Rueping,
• Teerawut Bootwicha,
• Hannah Baars and
• Erli Sugiono

Beilstein J. Org. Chem. 2011, 7, 1680–1687, doi:10.3762/bjoc.7.198

• employing a heterogeneous solid acid catalyst [66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84]. The continuous-flow apparatus for the experiment was set up according to Scheme 1. A 10 mL reaction vessel was charged with the heterogeneous solid acid catalyst (10 g) and inserted

• . Our initial reaction development was focussed on finding the optimal conditions for the continuous-flow reaction of phenylacetylene (1a) with benzaldehyde (2a) applying the ion-exchange resin amberlyst-15 [85] as heterogeneous solid acid catalyst. The effects of the substrate concentration, the

• mixture of alkyne 1 and aldehyde 2 was constantly pumped into the flow cell, filled with the solid acid catalyst and solvent, at the flow rate of 0.5 mL min−1 under microwave irradiation. This was followed by a washing procedure with 100 mL of solvent and then the next substrate was introduced

Continuous proline catalysis via leaching of solid proline

• Suzanne M. Opalka,
• Ashley R. Longstreet and
• D. Tyler McQuade

Beilstein J. Org. Chem. 2011, 7, 1671–1679, doi:10.3762/bjoc.7.197

• precursors) that only partially or slowly dissolve into or react with the solution. (See Figure 1 for a comparison of solid catalysts that are used in flow.) Proline is an example of such a catalyst [19] (others include zero-valent transition metals, many solid acid catalysts, and other secondary amine

Phase- vanishing halolactonization of neat substrates

• Nicole Windmon and
• Veljko Dragojlovic

Beilstein J. Org. Chem. 2008, 4, No. 29, doi:10.3762/bjoc.4.29

• solidified at the interface of FC-72 and ester layers, preventing further reaction. Good stirring prevented formation of a solid layer. Alternatively, the solid layer was occasionally stirred with a small glass rod (a sealed capillary melting point tube) to break the clumps. Solid acid 14 reacted without an