On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• site-selective C(sp3)−H bond functionalization strategy (Scheme 28B) [160]. Starting from the abundant feedstock chemical cedrol, oxidation of the gem-dimethyl group was achieved on a gram scale, with the formation of a strained tetrahydrofuran ring. The latter was methylated and eliminated via the

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

• Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

• fluorine activation (see 22i–j), and the oxygen-containing natural terpenoid ambroxide was methylated at the methylene position next to the O atom on the tetrahydrofuran ring (see 22k). This manganese-catalyzed late-stage approach enables the direct methylation of unactivated C–H bonds with excellent site

Organocatalytic asymmetric Michael/acyl transfer reaction between α-nitroketones and 4-arylidenepyrrolidine-2,3-diones

• Chandrakanta Parida and
• Subhas Chandra Pan

Beilstein J. Org. Chem. 2021, 17, 1447–1452, doi:10.3762/bjoc.17.100

• enantioselectivities. A similar enantioselectivity was attained in α,α,α-trifluorotoluene and tetrahydrofuran as the solvent, whereas in chloroform a slightly improved enantioselectivity of 86% ee was observed. Finally, the best solvent was found to be 1,2-dichloroethane and the product 3a was obtained in 82% yield

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• -isobutyrylguanine, N-benzoylcytosine, 6-O-allylhypoxanthine or N,N-dibenzoyldiaminopurine in 53 to 83% yield. The desilylation of the nucleosides 3a–f with tetrabutylammonium fluoride in tetrahydrofuran (THF) led to the formation of six different double-headed nucleosides 4a–f (Scheme 1) [38][39]. The synthesized

• (Scheme 17) [54]. The tert-butyldimethylsilyl-protected (TBDMS) nucleoside 76 was first hydrolyzed using NaOH, which was followed by TBDMS deprotection using tetra-n-butylammonium fluoride (TBAF) in tetrahydrofuran (THF) to afford the double-headed nucleoside 77. The TBDMS-protected nucleoside 73 was

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• from the condensation reaction of aldehydes or ketones with tert-butanesulfinamides. In this work, the condensation with aldehydes was carried using Ti(OEt)4 in tetrahydrofuran (THF), or CuSO4 in dichloromethane at room temperature. The combination of MgSO4 in the presence of a catalytic amount of

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

• lines [59]. The synthesis was based on the reaction of commercially available aromatic amines with sodium dicyandiamide at 80 °C to obtain the corresponding aryldicyanoamides. The latter were then separately reacted with alkylamines or cycloalkylamines at 40 °C in tetrahydrofuran in the presence of

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

• 1,3-diaxial interaction, which favors the formation of tetrahydrofuran product 17 instead of the tetrahydropyran 16 (Scheme 4). Although the Prins cyclization is one of the powerful tools for the construction of 2,6-disubstituted THPs, there are some limitations that restrict a wide applicability. The

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

Synthesis and properties of oligonucleotides modified with an N-methylguanidine-bridged nucleic acid (GuNA[Me]) bearing adenine, guanine, or 5-methylcytosine nucleobases

• Naohiro Horie,
• Takao Yamaguchi,
• Shinji Kumagai and
• Satoshi Obika

Beilstein J. Org. Chem. 2021, 17, 622–629, doi:10.3762/bjoc.17.54

• acetonitrile, dichloromethane, and tetrahydrofuran (THF) were used as purchased. 1H, 13C, and 31P NMR spectra were recorded using a JEOL JNM-ECS300 spectrometer. The chemical shift values are expressed in δ values (ppm) relative to tetramethylsilane as an internal standard, CHCl3 (δ = 7.26 ppm) for 1H NMR

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

• chirality of lactic acid, three forms of PLA (ʟ, PLLA; ᴅ, PDLA; ᴅʟ, PDLLA) with slightly different properties (crystallinity, Tg 60–65 °C, Tm 130–180 °C) exist [256]. PLA is soluble in benzene, tetrahydrofuran, ethyl acetate, propylene carbonate and dioxane [257], and it is biodegradable [258][259]. Because

Synthesis of trifluoromethyl ketones by nucleophilic trifluoromethylation of esters under a fluoroform/KHMDS/triglyme system

• Yamato Fujihira,
• Yumeng Liang,
• Makoto Ono,
• Kazuki Hirano,
• Takumi Kagawa and
• Norio Shibata

Beilstein J. Org. Chem. 2021, 17, 431–438, doi:10.3762/bjoc.17.39

• effect on the yield of the reaction of 1g (Table 2, entries 3–6, 58–72%). Next, a range of common oxygen and sulfur-containing compounds such as furan, tetrahydrofuran, 1,4-dioxane, thiophene, benzo[b]thiophene, dibenzo[b,d]thiophene, and diphenylsulfane were also screened. These substances also have

Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring

• Daria I. Tonkoglazova,
• Anna V. Gulevskaya,
• Konstantin A. Chistyakov and
• Olga I. Askalepova

Beilstein J. Org. Chem. 2021, 17, 11–21, doi:10.3762/bjoc.17.2

• alternating enantiomers form a screw along the a axis. Optical properties All helicenes 10 are well soluble in dichloromethane and chloroform. Solubility in other common solvents such as acetonitrile, DMSO, tetrahydrofuran, ethanol and hexane is markedly lower. Carbazole-based [6]helicene 12 was described as

Naphthalonitriles featuring efficient emission in solution and in the solid state

• Sidharth Thulaseedharan Nair Sailaja,
• Iván Maisuls,
• Jutta Kösters,
• Alexander Hepp,
• Andreas Faust,
• Jens Voskuhl and
• Cristian A. Strassert

Beilstein J. Org. Chem. 2020, 16, 2960–2970, doi:10.3762/bjoc.16.246

• environment responsiveness is based on having variable substituents at the para-position of the two phenyl moieties. The excited state properties were fully investigated in tetrahydrofuran (THF) solutions and in THF/H2O mixtures. The size of the aggregates in aqueous media were measured by dynamic light

Vicinal difluorination as a C=C surrogate: an analog of piperine with enhanced solubility, photostability, and acetylcholinesterase inhibitory activity

• Yuvixza Lizarme-Salas,
• Alexandra Daryl Ariawan,
• Ranjala Ratnayake,
• Hendrik Luesch,
• Angela Finch and
• Luke Hunter

Beilstein J. Org. Chem. 2020, 16, 2663–2670, doi:10.3762/bjoc.16.216

• = tetrahydrofuran, AD-mix-α = commercially available asymmetric dihydroxylation reagent, TBAF = tetrabutylammonium fluoride, DeoxoFluor = bis(2-methoxyethyl)aminosulfur trifluoride. Synthesis of compound 2 via a stepwise fluorination approach (ester series). DIC = diisopropylcarbodiimide, HOBt

Synthesis of 4-substituted azopyridine-functionalized Ni(II)-porphyrins as molecular spin switches

• Jannis Ludwig,
• Tobias Moje,
• Fynn Röhricht and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2589–2597, doi:10.3762/bjoc.16.210

• procedure of Nishimura et al. using mercury acetate in trifluoroacetic acid and anisole as radical scavenger (Scheme 5) [34]. Cleavage of the tert-butyl protection group yielded the disulfide 1g, which was reduced with catecholborane in tetrahydrofuran to give the free thiol 1h, which readily reoxidizes

Water-soluble host–guest complexes between fullerenes and a sugar-functionalized tribenzotriquinacene assembling to microspheres

• Si-Yuan Liu,
• Xin-Rui Wang,
• Man-Ping Li,
• Wen-Rong Xu and
• Dietmar Kuck

Beilstein J. Org. Chem. 2020, 16, 2551–2561, doi:10.3762/bjoc.16.207

• -(OAcG)6 exhibited good solubility in most organic solvents such as dichloromethane, chloroform, tetrahydrofuran, and DMSO, but it was insoluble in solvents like methanol, ethanol, and water. Compound TBTQ-(OAcG)6 was finally deacetylated with sodium methoxide in methanol to afford the desired six-fold

• -2,3,4,6-tetraacetylglucose (1.48 g, 3.96 mmol), copper(II) sulfate pentahydrate (52 mg, 0.21 mmol), and sodium ascorbate (28 mg, 0.14 mmol) in tetrahydrofuran/water cosolvent 2:1 (10 mL, v/v) was stirred vigorously under nitrogen in the dark at 60 °C for 24 h. Then, the solvent was removed under reduced

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• enantioenriched tetrahydrofuran 256 in excellent yields and moderate enantioselectivities (14 examples, up to 82:18 er). Knowles et al. synthesised enantioenriched pyrroloindolines 257 from indoles 258 and TEMPO using an iridium-based photocatalyst and a similar chiral phosphate base 259 to that employed by Luo

Chan–Evans–Lam N1-(het)arylation and N1-alkеnylation of 4-fluoroalkylpyrimidin-2(1H)-ones

• Viktor M. Tkachuk,
• Oleh O. Lukianov,
• Mykhailo V. Vovk,
• Isabelle Gillaizeau and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2020, 16, 2304–2313, doi:10.3762/bjoc.16.191

• . Average product yields of 38–69% were observed for the reaction run in methanol, dichloroethane, tetrahydrofuran, and ethyl acetate (Table 1, entries 13–15, 20 and 21). In dimethyl carbonate and DMSO solutions, the yields were reduced to 4 and 11%, respectively (Table 1, entries 22 and 23). In contrast

Controlling the stereochemistry in 2-oxo-aldehyde-derived Ugi adducts through the cinchona alkaloid-promoted electrophilic fluorination

• Yuqing Wang,
• Gaigai Wang,
• Anatoly A. Peshkov,
• Ruwei Yao,
• Muhammad Hasan,
• Manzoor Zaman,
• Chao Liu,
• Stepan Kashtanov,
• Olga P. Pereshivko and
• Vsevolod A. Peshkov

Beilstein J. Org. Chem. 2020, 16, 1963–1973, doi:10.3762/bjoc.16.163

• preferred reaction medium for this process with acetonitrile, tetrahydrofuran, and dichloromethane being less efficient in terms of ee of the obtained product 12a (Table 3, entries 1–5). Using catalytic quantities of quinine led to a prolonged reaction time and diminished yield and ee of 12a compared to the

Regiodivergent synthesis of functionalized pyrimidines and imidazoles through phenacyl azides in deep eutectic solvents

• Paola Vitale,
• Luciana Cicco,
• Ilaria Cellamare,
• Filippo M. Perna,
• Antonio Salomone and
• Vito Capriati

Beilstein J. Org. Chem. 2020, 16, 1915–1923, doi:10.3762/bjoc.16.158

• ][3]. As part of our ongoing research in DES chemistry, we reported recently on the preparation of valuable heterocycles by (a) nucleophilic substitution (tetrahydrofuran derivatives) [4], (b) heterocyclodehydration reactions (2-aminoimidazoles, 2-pyrazinones, benzoxazines, thiophenes) [5][6][7][8

Rearrangement of o-(pivaloylaminomethyl)benzaldehydes: an experimental and computational study

• Csilla Hargitai,
• Györgyi Koványi-Lax,
• Tamás Nagy,
• Péter Ábrányi-Balogh,
• András Dancsó,
• Gábor Tóth,
• Judit Halász,
• Angéla Pandur,
• Gyula Simig and
• Balázs Volk

Beilstein J. Org. Chem. 2020, 16, 1636–1648, doi:10.3762/bjoc.16.136

• under the same conditions in tetrahydrofuran (THF) instead of DCM, substantially less dimer-like product 3a or 3b was formed in favor of the rearranged aldehyde 2a or 2b. When starting from aldehyde 1c [2], containing the methoxy function in the ortho position of the formyl moiety and meta to the

Synthesis of new dihydroberberine and tetrahydroberberine analogues and evaluation of their antiproliferative activity on NCI-H1975 cells

• Giacomo Mari,
• Lucia De Crescentini,
• Serena Benedetti,
• Francesco Palma,
• Stefania Santeusanio and
• Fabio Mantellini

Beilstein J. Org. Chem. 2020, 16, 1606–1616, doi:10.3762/bjoc.16.133

• achieved as a pure pale yellow solid directly from the reaction medium with the best yields (Table 1, entry 7). In tetrahydrofuran (THF), in ethyl acetate (EtOAc), and in alcohols such as methanol, ethanol, isopropanol (MeOH, EtOH, iPrOH) the reaction furnishes a complicate profile, where the desired 2a is

Mechanochemical green synthesis of hyper-crosslinked cyclodextrin polymers

• Alberto Rubin Pedrazzo,
• Fabrizio Caldera,
• Marco Zanetti,
• Silvia Lucia Appleton,
• Nilesh Kumar Dhakar and
• Francesco Trotta

Beilstein J. Org. Chem. 2020, 16, 1554–1563, doi:10.3762/bjoc.16.127

• extraction with acetone). Moreover, this could be also explained since not all the reactive groups are freely accessible within the NS structure. Carbonyl diimidazole can react with carboxylic acids at room temperature in many aprotic solvents (such as tetrahydrofuran, DMSO, or DMF) to form imidazolides in

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• tetrahydrofuran (8.1), giving access to the key C(sp3) radical. The nickel catalyst, after an oxidative addition with the aryl bromide 8.2 and intercepting the alkyl radical species, gave the radical cross-coupling product 8.3 upon a reductive elimination. Other diaryl ketone dyes, such as 9-fluorenone, have been

• system to perform a ring closure/pyridylation radical cascade for the synthesis of tetrahydrofuran derivatives (Scheme 39b) [161]. Eosin Y (OD13) has been demonstrated to be another competent photocatalyst for the generation of O-centered radicals from N-alkoxypyridynium salts. These radicals have been

• , including eosin Y (OD13) [163] and acridine red [164]. Wang and co-workers relied on this approach for the development of an organophotocatalytic vinylation of tetrahydrofuran derivatives with alkynes (Scheme 40) [165]. In this method, the photoexcited OD13 induces the cleavage of the weak O–O bond of tert

Synthesis and properties of quinazoline-based versatile exciplex-forming compounds

• Rasa Keruckiene,
• Simona Vekteryte,
• Ervinas Urbonas,
• Matas Guzauskas,
• Eigirdas Skuodis,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 1142–1153, doi:10.3762/bjoc.16.101

• polarities, i.e., toluene (0.099), tetrahydrofuran (0.207) and dimethylformamide (0.4) (values in parentheses are the solvent polarities relative to water) [21]. The PL spectra of the solutions of compound 3 appeared to be solvent-polarity independent as only the structured emission band of the locally