Regioselective quinazoline C2 modifications through the azide–tetrazole tautomeric equilibrium

• Dāgs Dāvis Līpiņš,
• Andris Jeminejs,
• Una Ušacka,
• Anatoly Mishnev,
• Māris Turks and
• Irina Novosjolova

Beilstein J. Org. Chem. 2024, 20, 675–683, doi:10.3762/bjoc.20.61

• product. Compounds 12 did not tolerate aqueous conditions or high temperatures and have also been observed to degrade under direct sunlight. Next, a stepwise one-pot approach was investigated to increase the overall yield (Scheme 6). The reaction in anhydrous DMF yielded a mixture of the desired product

Enabling artificial photosynthesis systems with molecular recycling: A review of photo- and electrochemical methods for regenerating organic sacrificial electron donors

• Grace A. Lowe

Beilstein J. Org. Chem. 2023, 19, 1198–1215, doi:10.3762/bjoc.19.88

• appropriate. EDTA has the highest reported oxidation potential and is the least reducing member of the amines shown (1.41 V vs SCE). Hence, it should only regenerate photooxidized Ru(bpy)3 in aqueous conditions. Unfortunately, Carpenter and co-workers did not measure the oxidation potential of their

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

• nanoorganocatalysts. Various solvent systems, such as aqueous conditions, different organic solvents, solvent-free conditions, ionic liquids, and DESs, have been reported in modified Clauson–Kaas reactions at room temperature, under thermal and microwave-assisted conditions. In the Clauson–Kaas reaction mechanism

• amines 30 and 2,5-dimethoxytetrahydrofuran (2) under aqueous conditions (Scheme 14). Among various solvents used to optimize the reaction conditions, H2O proved to be the best solvent for these transformations. Azizi and co-workers [68] described a one step, economical, and green method for the synthesis

• ). This reaction has been successfully used for common amines using acetic acid and water, but benzylamines and benzamides show no reaction under aqueous conditions. In the case of amino acid ester hydrochlorides, the reaction to give pyrrole can be carried out without the need for the two-phase

An efficient metal-free and catalyst-free C–S/C–O bond-formation strategy: synthesis of pyrazole-conjugated thioamides and amides

• Shubham Sharma,
• Dharmender Singh,
• Sunit Kumar,
• Vaishali,
• Rahul Jamra,
• Naveen Banyal,
• Deepika,
• Chandi C. Malakar and
• Virender Singh

Beilstein J. Org. Chem. 2023, 19, 231–244, doi:10.3762/bjoc.19.22

• amounts of β-cyclodextrin (β-CD) [81] under aqueous conditions at room temperature as well as under heating at 100 °C (entries 1 and 2, Table 1). Unfortunately, the model reactants remained unreacted and similar observations were recorded using a mixture of H2O/MeOH 1:4, and methanol as a reaction medium

Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions

• Surendran Amrutha,
• Sankaran Radhika and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 262–285, doi:10.3762/bjoc.18.31

• for the effective Sonogashira coupling under aqueous conditions (Scheme 3) [22]. The coupling reaction was catalyzed by the nanoparticles in water between room temperature and 45 °C. Notably, the amount of Pd was below the detection limit. The reaction done in the presence of 1000 ppm of Pd ligated

Host–guest interaction and properties of cucurbit[8]uril with chloramphenicol

• Lin Zhang,
• Jun Zheng,
• Guangyan Luo,
• Xiaoyue Li,
• Yunqian Zhang,
• Zhu Tao and
• Qianjun Zhang

Beilstein J. Org. Chem. 2021, 17, 2832–2839, doi:10.3762/bjoc.17.194

• under neutral aqueous conditions. ITC study of the interaction between CPE and Q[8] ITC is a highly sensitive and automated microcalorimeter method, which can continuously and accurately monitor and record the calorimetric curve of each process to obtain the thermodynamic parameters and action ratio

An initiator- and catalyst-free hydrogel coating process for 3D printed medical-grade poly(ε-caprolactone)

• Jochen Löblein,
• Thomas Lorson,
• Miriam Komma,
• Tobias Kielholz,
• Maike Windbergs,
• Paul D. Dalton and
• Robert Luxenhofer

Beilstein J. Org. Chem. 2021, 17, 2095–2101, doi:10.3762/bjoc.17.136

• coating and monomer concentration (Supporting Information File 1, Figure S2). As the next step, scaffolds were investigated with respect to their wettability. In order to simulate aqueous conditions in cell culture medium or after implantation, samples were immersed in water for 0, 10, 20 and 30 min

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• benzoxazoles might be explained by the subsequent hydrolysis of this relatively fragile ring under the strongly acidic aqueous conditions. Recently, a protocol using a Lewis acid (AlCl3) as an activating agent of the cyanoguanidine in dry THF allowed improving the yields up to 70% (Scheme 11B) [32]. Related

• reported by Lebel et al. [52] and McMorran et al. [53], both using overnight heating in acidic aqueous conditions (Scheme 22). The authors reported moderate to good product yields, and the final compounds found applications as intermediates for dynamic materials [52] and ligands for nickel complexation [53

Metal-free glycosylation with glycosyl fluorides in liquid SO₂

• Krista Gulbe,
• Jevgeņija Lugiņina,
• Edijs Jansons,
• Artis Kinens and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 964–976, doi:10.3762/bjoc.17.78

• oligosaccharides and glycopeptides under basic aqueous conditions [32][33]. Nevertheless, most of the conventional conditions for glycosyl fluoride activation have considerable drawbacks in terms of atom efficiency and environmental impact. These methods generally require (1) stoichiometric amounts of promoters

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

• -ones 24 using substituted phenylenediamine 23, aldehydes 5 and cyclic 1,3-diketone such as tetronic acid 6c under microwave irradiation in aqueous conditions delivering the product in good yields (70–89%). The use of a non-polar solvent resulted in the formation of side products like benzimidazole

The biomimetic synthesis of balsaminone A and ellagic acid via oxidative dimerization

• Sharna-kay Daley and
• Nadale Downer-Riley

Beilstein J. Org. Chem. 2020, 16, 2026–2031, doi:10.3762/bjoc.16.169

• 16 in 29, 34, and 19% yields, respectively (Table 1). As anticipated, the reaction of naphthalene 17 with CAN under aqueous conditions resulted in preferential oxidative demethylation to give quinone 7, as opposed to oxidative dimerization. The elimination of water from the reaction posed a few

• aqueous conditions to prevent complexation of the reagent and the starting material. Of the Lewis acids used, stannic chloride proved to be the most effective oxidant for dimerization (Table 1). However, the hypervalent iodine reagents PIFA and PIDA gave better results overall, affording dimer 18 in 63

An overview of the cycloaddition chemistry of fulvenes and emerging applications

• Ellen Swan,
• Kirsten Platts and
• Anton Blencowe

Beilstein J. Org. Chem. 2019, 15, 2113–2132, doi:10.3762/bjoc.15.209

• reactive, is prone to dimerization and polymerisation [59][111]. If the reaction is conducted under aqueous conditions, the probability of dimerization has been reported to increase further due to hydrophobic packing of the fulvene molecules [120][121]. Intramolecular cycloadditions Whilst not as widely

• ][172][174][176][183][186][227][229]. There are very few papers reporting the aforementioned reaction occurring in aqueous conditions [175] most likely as a result of the poor solubility of fulvene derivatives in water [175]. Although the stereochemistry of DACs can usually be predicted by the ‘endo

Homo- and hetero-difunctionalized β-cyclodextrins: Short direct synthesis in gram scale and analysis of regiochemistry

• Gábor Benkovics,
• Mihály Bálint,
• Éva Fenyvesi,
• Erzsébet Varga,
• Szabolcs Béni,
• Konstantina Yannakopoulou and
• Milo Malanga

Beilstein J. Org. Chem. 2019, 15, 710–720, doi:10.3762/bjoc.15.66

• proves that tosylation of 6-monoazido-β-CD under Cu(II)-assisted aqueous conditions is also a side-selective process, with a slight preference towards the formation of the 6A,6D–6D,6A-disubstituted product. Conclusion In the development of a direct strategy for β-CD difunctionalization, several focal

Ammonium-tagged ruthenium-based catalysts for olefin metathesis in aqueous media under ultrasound and microwave irradiation

• Łukasz Gułajski,
• Andrzej Tracz,
• Katarzyna Urbaniak,
• Stefan J. Czarnocki,
• Michał Bieniek and
• Tomasz K. Olszewski

Beilstein J. Org. Chem. 2019, 15, 160–166, doi:10.3762/bjoc.15.16

• NHC ligand. This result suggests that a fast propagation ensured by a smaller carbene ligand rather than robustness ascribed to larger catalysts is a prerequisite for the efficient metathesis in homogeneous aqueous conditions. Except in the case of catalyst 3a, exhibiting the lowest activity under

Water-soluble SNS cationic palladium(II) complexes and their Suzuki–Miyaura cross-coupling reactions in aqueous medium

• Alphonse Fiebor,
• Richard Tia,
• Banothile C. E. Makhubela and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1859–1870, doi:10.3762/bjoc.14.160

• solvents in the presence of an excess of base [1][2][3]. With the drive for the development of environmentally friendly and low cost protocols, a number of methodologies for the Suzuki–Miyaura reaction under aqueous conditions or in neat water have been reported [4][5][6]. This has been achieved via

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• benefits both in terms of efficiency (reducing total processing times from weeks to hours) and by minimising exposure to aqueous conditions, access to previously elusive materials. In the absence of large quantities of solvent and heating, side-reactions can be reduced or eliminated. The central

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• Aggarwal et al. [80][89] under aqueous conditions. The reaction exhibited a high level of chemoselectivity and regiospecificity yielding 2-(3-methylpyrazol-1-yl)-5-methylpyrazolo[1,5-a]pyrimidines 120 out of the four possible isomers (Scheme 33). In the case of arylbutadiones, formation of two more

One-pot syntheses of blue-luminescent 4-aryl-1H-benzo[f]isoindole-1,3(2H)-diones by T3P^® activation of 3-arylpropiolic acids

• Melanie Denißen,
• Alexander Kraus,
• Guido J. Reiss and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2017, 13, 2340–2351, doi:10.3762/bjoc.13.231

• electro-neutral substrates are equally well tolerated (Table 2, entries 1–3), while the electron-poor derivative 1d results in a slightly decreased yield of 88% due to the increased formation of side products (Table 2, entry 4). Expectedly, the products 2 are not stable under acidic aqueous conditions

An efficient Pd–NHC catalyst system in situ generated from Na₂PdCl₄ and PEG-functionalized imidazolium salts for Mizoroki–Heck reactions in water

• Nan Sun,
• Meng Chen,
• Liqun Jin,
• Wei Zhao,
• Baoxiang Hu,
• Zhenlu Shen and
• Xinquan Hu

Beilstein J. Org. Chem. 2017, 13, 1735–1744, doi:10.3762/bjoc.13.168

• the palladium complex in Mizoroki–Heck reactions. Furthermore, the TON of the coupling of 4-bromoacetophenone (1a) and styrene (2a) with Na2PdCl4/L1 as the catalyst was calculated to be 10,000, which is much higher than for previously reported catalytic systems under aqueous conditions. After

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

• A. Michael Downey and
• Michal Hocek

Beilstein J. Org. Chem. 2017, 13, 1239–1279, doi:10.3762/bjoc.13.123

• remarkably simple protocol that allows for a C3′-regioselective glycosylation of unprotected sucrose under aqueous conditions has been described by Schepartz, Miller and colleagues [57]. They took advantage of the fact that most glycosyl transferase enzymes operate in a divalent metal cation-dependent

• transformations to occur completely devoid of protection on the other hydroxy groups (Figure 4). Many of these reactions also take place under aqueous conditions which adds increased potential for the widespread use of these agents. These strategies appear more idealized than the indirect activation methods

• determine the organic composition [101]. The easiness of this procedure is noteworthy. By simple pH adjustments in a two-step process a functionalized glycan-surface array can be obtained using a fully unprotected saccharide donor under aqueous conditions. 5 In situ activation of the anomeric center In this

Solvent-free synthesis of novel para-menthane-3,8-diol ester derivatives from citronellal using a polymer-supported scandium triflate catalyst

• Lubabalo Mafu,
• Ben Zeelie and
• Paul Watts

Beilstein J. Org. Chem. 2016, 12, 2046–2054, doi:10.3762/bjoc.12.193

• environmentally friendly method for the synthesis of para-menthane-3,8-diol from natural citronellal oil in 96% yield, under solvent free aqueous conditions. The acylation of para-menthane-3,8-diol with various acid anhydrides over polymer-supported scandium triflate (PS-Sc(OTf)3) catalyst was subsequently

Nucleic acids through condensation of nucleosides and phosphorous acid in the presence of sulfur

• Tuomas Lönnberg

Beilstein J. Org. Chem. 2016, 12, 670–673, doi:10.3762/bjoc.12.67

• phosphorous acid are hydrolytically stable compounds that are readily formed upon concentration of aqueous solutions of alcohols and phosphite salts [12]. The monoesters may react further to H-phosphonate diesters but this is an equilibrium process that under aqueous conditions favors the starting materials

New synthetic strategies for xanthene-dye-appended cyclodextrins

• Milo Malanga,
• Andras Darcsi,
• Mihaly Balint,
• Gabor Benkovics,
• Tamas Sohajda and
• Szabolcs Beni

Beilstein J. Org. Chem. 2016, 12, 537–548, doi:10.3762/bjoc.12.53

• dyes and coupling agents, thus having clear potential for multigram scale-up. The mild, aqueous conditions, as well as the simplicity of the synthesis, make these reactions attractive tools for the preparation of fluorescent cyclodextrins connected through an amide bond. The obtained products were

Catalytic asymmetric formal synthesis of beraprost

• Yusuke Kobayashi,
• Ryuta Kuramoto and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2015, 11, 2654–2660, doi:10.3762/bjoc.11.285

• [4][5]. However, PGI2 possesses an unstable enol ether moiety, which can be hydrolyzed even under neutral aqueous conditions, resulting in a loss of pharmacological action [6][7][8]. Therefore, an increasing number of more stable PGI2 derivatives have been developed. Among these, beraprost (1) has

Azobenzene-based inhibitors of human carbonic anhydrase II

• Leander Simon Runtsch,
• David Michael Barber,
• Peter Mayer,
• Michael Groll,
• Dirk Trauner and
• Johannes Broichhagen

Beilstein J. Org. Chem. 2015, 11, 1129–1135, doi:10.3762/bjoc.11.127

• wavelength of maximal absorption (λmax) by RP–LCMS equipped with a UV–vis diode array detector, when determining the purity of our library. Therefore, λmax is determined in a water/acetonitrile mixture, which mimics aqueous conditions that are also used for the biological assays. The results are given in