Advancements in hydrochlorination of alkenes

• Daniel S. Müller

Beilstein J. Org. Chem. 2024, 20, 787–814, doi:10.3762/bjoc.20.72

• (anti-Markovnikov product). One plausible explanation for this intriguing observation is that K10 and other zeolites may function both as Brønsted acids and radical initiators [63]. Consequently, it is likely that both ionic and radical pathways are concurrently in operation. The in situ generation of

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

1-Butyl-3-methylimidazolium tetrafluoroborate as suitable solvent for BF₃: the case of alkyne hydration. Chemistry vs electrochemistry

• Marta David,
• Elisa Galli,
• Richard C. D. Brown,
• Marta Feroci,
• Fabrizio Vetica and
• Martina Bortolami

Beilstein J. Org. Chem. 2023, 19, 1966–1981, doi:10.3762/bjoc.19.147

• ], Pd(II) [31][32][33], Pt(II) [34][35], Fe(III) [36][37], Cu(I) [38][39][40][41], Co(III) [42][43][44], as well as other metals, have been widely studied. In addition, methods involving Brønsted acids, alone or in presence of Lewis acids as co-catalysts, have been developed [45][46][47][48][49][50][51

• ][52][53][54]. However, some of these procedures suffer from major drawbacks, such as the toxicity and/or high cost of the metal catalysts, the need to use concentrated Brønsted acids in high excess, long reaction times, and high temperatures. In addition, these reactions have been studied mainly in

Lewis acid-promoted direct synthesis of isoxazole derivatives

• Dengxu Qiu,
• Chenhui Jiang,
• Pan Gao and
• Yu Yuan

Beilstein J. Org. Chem. 2023, 19, 1562–1567, doi:10.3762/bjoc.19.113

• environmentally friendly catalysts, our laboratory recently developed an alternative approach to the synthesis of isooxazoles starting from 2-methylquinoline and alkynes mediated by Brønsted acids in good yields (Scheme 1, reaction 3) [20]. The utilization of main element metal aluminum salts in organic synthesis

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

Synthesis of tetrahydrofuro[3,2-c]pyridines via Pictet–Spengler reaction

• Elena Y. Mendogralo and
• Maxim G. Uchuskin

Beilstein J. Org. Chem. 2023, 19, 991–997, doi:10.3762/bjoc.19.74

• hydrolysis could be a convenient tool for the synthesis of substituted 3-(2-oxopropyl)piperidin-4-ones 5. Using tetrahydrofuro[3,2-c]pyridine 4a as the model compound, we studied the effect of various Brønsted acids, temperature, concentrations, and the nature of the solvent on the efficiency of the reaction

Aromatic C–H bond functionalization through organocatalyzed asymmetric intermolecular aza-Friedel–Crafts reaction: a recent update

• Anup Biswas

Beilstein J. Org. Chem. 2023, 19, 956–981, doi:10.3762/bjoc.19.72

• –Crafts reaction has also been explored under the influence of organocatalysis. However, here organocatalysts act as Brønsted acids which form noncovalent interactions (H-bonding) with the imine nitrogen to enhance the electrophilicity of the imine component. In addition, by selecting suitable imine

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

• conditions (Scheme 10). Green chemistry approach for the Clauson–Kaas synthesis of N-substituted pyrroles This section describes the Clauson-Kaas pyrrole syntheses using different greener methods in the presence of various Brønsted acids or Lewis acids. These include reactions in aqueous media, under solvent

• -catalyzed reactions under heating conditions. However, due to environmental concerns, the second part of this review focuses on greener Clauson–Kaas reaction protocols. Various Brønsted acids, Lewis acids, transition metal catalysts, and organocatalysts have been used in water as a green solvent, under

Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles

• Bilge Banu Yagci,
• Selin Ezgi Donmez,
• Onur Şahin and
• Yunus Emre Türkmen

Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6

• ester 36 with an n-propyl group at the β-position is that it does not have the volatility issues of the ethyl-substituted ester, and that it is sterically less hindered than the isobutyl-substituted ester. When a broad range of Lewis and Brønsted acids such as AgOTf, Zn(OTf)2, ZnBr2, CuCl2, BF3·OEt2

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• ]. The well-known and convenient classification of organocatalysts into Lewis bases, Lewis acids, Brønsted bases, and Brønsted acids [1] also leaves the redox-organocatalysts behind. Moreover, in numerous research papers employing redox-active molecules as catalysts the developed processes are not

• -organocatalysts. Organocatalysis classification used in the present perspective. Oxidative processes catalyzed by amines. N-Heterocyclic carbene (NHC) catalysis in oxidative functionalization of aldehydes. Examples of asymmetric oxidative processes catalyzed by chiral Brønsted acids. Asymmetric aerobic α

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

• with N-bromosuccinimide (NBS) was carried out in toxic polar solvents (e.g., DMF), but no iodinated or chlorinated products were obtained because of the low reactivity of NIS and NCS (Scheme 1a) [24][25][26][27]. In recent time, the use of Lewis or Brønsted acids, Lewis bases, and transition-metal

New advances in asymmetric organocatalysis

• Radovan Šebesta

Beilstein J. Org. Chem. 2022, 18, 240–242, doi:10.3762/bjoc.18.28

• transformations using chiral Brønsted acids, Brønsted base, and hydrogen bond donors. Recently noncovalent activation continues to expand into other types of weak attractive interactions such as halogen and chalcogen bonds. Not surprisingly, all activation modes allow further expansion and diversification via a

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

• Scott Benz and
• Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

• later explored alternative Brønsted and Lewis acids that could effectively catalyze the rearrangement of symmetric α‑hydroxy aldimines [29]. A catalyst screen was performed on the model substrate 97a (97 with R = Ph; Figure 19a) using three different Brønsted acids (acetic acid, sulfuric acid, and p

• rearrangements catalyzed by silica gel and montmorillonite K 10. a) For 102a (102 with R = Ph), silica gel and montmorillonite K 10 gave ≥95% yields, while Brønsted acids, other Lewis acids, and NaOEt generally performed much more poorly. b) Electron-rich R groups rearrange efficiently in the presence of silica

Enantioselective PCCP Brønsted acid-catalyzed aminalization of aldehydes

• Martin Kamlar,
• Robert Reiberger,
• Martin Nigríni,
• Ivana Císařová and
• Jan Veselý

Beilstein J. Org. Chem. 2021, 17, 2433–2440, doi:10.3762/bjoc.17.160

• Abstract Here we present an enantioselective aminalization of aldehydes catalyzed by Brønsted acids based on pentacarboxycyclopentadienes (PCCPs). The cyclization reaction using readily available anthranilamides as building blocks provides access to valuable 2,3-dihydroquinazolinones containing one

• chiral Brønsted acids. In the scope of Brønsted acid catalysis, chiral phosphoric acids (CPA) are dominating as potent catalysts in various asymmetric transformations [19][20][21][22][23], although the synthesis of these catalysts is expensive and laborious [24]. One of the most frequent examples of CPAs

• employed as catalysts in asymmetric dihydroquinazolinone synthesis [18]. Regarding the above-mentioned strategies involving chiral Brønsted acids, we envisioned that chiral pentacarboxycyclopentadiene (PCCP) derivatives could be used in the enantioselective aminalization of aldehydes with anthranilamide

Transition-metal-free intramolecular Friedel–Crafts reaction by alkene activation: A method for the synthesis of some novel xanthene derivatives

• Tülay Yıldız,
• İrem Baştaş and
• Hatice Başpınar Küçük

Beilstein J. Org. Chem. 2021, 17, 2203–2208, doi:10.3762/bjoc.17.142

• gold(III) [43], iridium(III) [44][45], iron(III) [46], or bismuth(III) [47][48] were used as catalysts for the intermolecular hydroarylation of unactivated alkenes. Organic Brønsted acids were also used as catalysts in a smaller number of studies [49][50]. In this work, we searched for some organic

• Brønsted acids and Lewis acids as catalysts (Table 1) to develop an intramolecular FCA protocol with activating alkenes effectively and economically in order to obtain some originally substituted arylxanthenes under mild conditions for the first time. We found that, among these acids, trifluoroacetic acid

• development trials for the synthesis of xanthene derivatives were carried out. For this purpose, catalyst researches were carried out using compound 4a. An intramolecular Friedel–Crafts reaction was tried by activating the alkene with various organic Brønsted acids and Lewis acids (Table 1). In the reaction

Chemical syntheses and salient features of azulene-containing homo- and copolymers

• Vijayendra S. Shetti

Beilstein J. Org. Chem. 2021, 17, 2164–2185, doi:10.3762/bjoc.17.139

• dehalogenative polycondensation reaction of 1,3-dibromoazulene (4) by an organonickel catalyst (Yamamoto protocol) yielded 1,3-polyazulene 5. The polymer was partially soluble in many organic solvents such as chloroform, THF, xylenes, DMF, N-methylpyrrolidone (NMP), and also in Brønsted acids like TFA and conc

Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• stereogenic centers. Review A plethora of highly effective small‐molecule organocatalysts have enriched the field of organic synthesis [27], including chiral proline derivatives, N‐heterocyclic carbenes, chiral thioureas and Brønsted acids as well as phase‐transfer catalysts (PTC), such as the quaternary

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

• described how attempts to synthesize 22-1 proved to be unsatisfactory [42] and in 1995, they reported their synthesis characterized only by 19F NMR and described that the salts were moisture-sensitive [84]. The synthesis is sensitive to solvents and the amount of Brønsted acids (HX). N,N’-Difluoro-1,4

Iodine-catalyzed electrophilic substitution of indoles: Synthesis of (un)symmetrical diindolylmethanes with a quaternary carbon center

• Thanigaimalai Pillaiyar,
• Masoud Sedaghati,
• Andhika B. Mahardhika,
• Lukas L. Wendt and
• Christa E. Müller

Beilstein J. Org. Chem. 2021, 17, 1464–1475, doi:10.3762/bjoc.17.102

• derivatives have recently received increasing attention from synthetic organic chemists, biologists, and pharmacologists. In general, DIMs can be synthesized via electrophilic substitution of indoles by aldehydes or ketones in the presence of conventional Lewis or Brønsted acids as catalysts [19]. This

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• ion, which was followed by a completely diastereoselective Friedel–Crafts reaction (Scheme 70). List and co-workers devised a strategy employing highly acidic confined iminoimidodiphosphate (iIDP) Brønsted acids 308 that catalyzed asymmetric Prins cyclizations of both aliphatic and aromatic aldehydes

An atom-economical addition of methyl azaarenes with aromatic aldehydes via benzylic C(sp³)–H bond functionalization under solvent- and catalyst-free conditions

• Divya Rohini Yennamaneni,
• Vasu Amrutham,
• Krishna Sai Gajula,
• Rammurthy Banothu,
• Murali Boosa and
• Narender Nama

Beilstein J. Org. Chem. 2020, 16, 3093–3103, doi:10.3762/bjoc.16.259

• functionalization [21][22]. The synthesis of pyridine and related azaarene derivatives involve the C(sp3)–H activation of 2-methylpyridines using different transition-metal compounds, Lewis acids, and Brønsted acids [23][24][25][26][27][28]. Recently, C(sp3)–H functionalizations of methylazaarenes with isatins and

Natural dolomitic limestone-catalyzed synthesis of benzimidazoles, dihydropyrimidinones, and highly substituted pyridines under ultrasound irradiation

• Kumar Godugu,
• Venkata Divya Sri Yadala,
• Mohammad Khaja Mohinuddin Pinjari,
• Trivikram Reddy Gundala,
• Lakshmi Reddy Sanapareddy and
• Chinna Gangi Reddy Nallagondu

Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156

• pharmacological properties [32][33][34][35][36][37]. A wide variety of Brønsted acids and Lewis acids are employed as efficient catalysts for the Biginelli reaction [38][39][40][41][42][43][44][45][46][47]. In addition, some transition metal-based catalysts and a few nonacidic inorganic salts are also utilized as

The charge-assisted hydrogen-bonded organic framework (CAHOF) self-assembled from the conjugated acid of tetrakis(4-aminophenyl)methane and 2,6-naphthalenedisulfonate as a new class of recyclable Brønsted acid catalysts

• Svetlana A. Kuznetsova,
• Alexander S. Gak,
• Yulia V. Nelyubina,
• Vladimir A. Larionov,
• Han Li,
• Michael North,
• Vladimir P. Zhereb,
• Alexander F. Smol'yakov,
• Artem O. Dmitrienko,
• Michael G. Medvedev,
• Igor S. Gerasimov,
• Ashot S. Saghyan and
• Yuri N. Belokon

Beilstein J. Org. Chem. 2020, 16, 1124–1134, doi:10.3762/bjoc.16.99

• that are insoluble in organic solvents and derived from the neutralization of polyacidic and polybasic tectones could be good candidates for becoming efficient heterogeneous Brønsted acids. Herein, we report the synthesis of a novel, purely organic, charge-assisted hydrogen-bonded self-assembled

• applications of the material. Thus, the catalytic properties of uncrystallized F-1 and F-1 with an F-1a phase were explored in a series of reactions typically promoted by Brønsted acids, such as epoxide ring openings with methanol and water (Scheme 2). The reactions were conducted at room temperature, and

Asymmetric synthesis of CF₂-functionalized aziridines by combined strong Brønsted acid catalysis

• Xing-Fa Tan,
• Fa-Guang Zhang and
• Jun-An Ma

Beilstein J. Org. Chem. 2020, 16, 638–644, doi:10.3762/bjoc.16.60

• ; difluoromethyl compounds; fluorinated diazo reagents; strong Brønsted acids; Introduction Chiral aziridines are prevalently found in natural products and artificially made bioactive molecules, thus receiving significant attention in the past decades [1][2][3][4][5][6]. Among them, the introduction of fluorine

• no enantioselectivity at all. As arylboronic acids have been harnessed to enhance the Brønsted acidity in asymmetric organocatalysis in combination with chiral diols or chiral aminoalcohols [40][41][42][43][44], we envisioned that the simultaneous use of arylboronic acids and chiral Brønsted acids

• limited Brønsted acidity of chiral phosphoric acids. Bearing this in mind, we then turned our attention to chiral disulfonimides developed by List, which have been established as a unique type of stronger Brønsted acids [45]. Putting it into practice, a range of BINOL-derived disulfonimides was used as

Oligomeric ricinoleic acid preparation promoted by an efficient and recoverable Brønsted acidic ionic liquid

• Fei You,
• Xing He,
• Song Gao,
• Hong-Ru Li and
• Liang-Nian He

Beilstein J. Org. Chem. 2020, 16, 351–361, doi:10.3762/bjoc.16.34

• be used as catalyst in the synthesis of oligomeric ricinoleic acid, the estolide with an acid value of 48 ± 2.5 mg KOH/g was obtained after 14 h [28]. Nevertheless, the product separation and catalyst reusability have not yet been investigated until now. Based on the fact that Brønsted acids present