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

• , namely pyrrolino-tetrahydroberberines, synthesized by some of us [68], exhibited enhanced antioxidant properties in comparison to THBER against a wide variety of pathophysiologically relevant oxidants such as peroxyl radicals, ferrous ion, and hydrogen peroxide [65]. In continuation of our ongoing

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

Synthesis of 3-substituted isoxazolidin-4-ols using hydroboration–oxidation reactions of 4,5-unsubstituted 2,3-dihydroisoxazoles

• Lívia Dikošová,
• Júlia Laceková,
• Ondrej Záborský and
• Róbert Fischer

Beilstein J. Org. Chem. 2020, 16, 1313–1319, doi:10.3762/bjoc.16.112

• isoxazolidin-4-ols. The strategy relies on a highly regio- and trans-stereoselective hydroboration–oxidation reaction of the 4,5-unsubstituted 2,3-dihydroisoxazoles with basic hydrogen peroxide. The consecutive oxidation/reduction route, sequentially employing Dess–Martin periodinane and ʟ-selectride, is used

• hydroxylamines using malonoyl peroxide, providing N-tosylated 3-aryl-substituted 4-hydroxyisoxazolidines in a highly stereoselective manner in favor of the C-3/4-trans isomers [27]. We believe that the 3-substituted isoxazolidin-4-ols, represented by the general structures of the trans and the cis stereoisomer 3

• -hydroxyisoxazolidines by the treatment of boronic ester-substituted isoxazolidines with basic hydrogen peroxide has previously been described [30][31]. To start with, the phenyl-substituted 2,3-dihydroisoxazole 5a was chosen as the starting substrate. After optimizing Kang's reaction conditions in terms of the borane

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• , arylalkyl, and diaryl oxime radicals was also studied by EPR spectroscopy [53]. Radicals were generated under inert atmosphere directly in the EPR cavity by photolysis of the added di-tert-butyl peroxide (Scheme 1). The authors pointed out the complexity of the processes of iminoxyl radicals’ decomposition

• iminoxyl radical 90. Presumably, the radical 90 underwent cyclization involving the azo group to form indazole 91. During the photolysis of a mixture of di-tert-butyl peroxide with oxime 92 containing an alkenyl fragment at temperatures from −30 to −10 °C, two signals were observed in the EPR spectrum with

• -system. According to EPR data, the authors suggested that iminoxyl radicals 101 generated from oximes 100 by photolysis with the addition of the di-tert-butyl peroxide gave nitroxides 102 [123]. The widespread use of iminoxyl radicals in organic synthesis involving a radical addition to a C=C bond

Activated carbon as catalyst support: precursors, preparation, modification and characterization

• Melanie Iwanow,
• Tobias Gärtner,
• Volker Sieber and
• Burkhard König

Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104

• the surface of the treated carbons in form of carboxyl groups, ketones, ether groups and carboxyl-carbonate structures is higher using nitric acid compared to hydrogen peroxide [116]. Nitrogen adsorption–desorption isotherms: The surface area and pore size distribution of solid catalyst materials can

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

• the peroxo radical III when using O2. Nicewicz and co-workers noticed that the presence of nucleophilic peroxide radicals generated from O2 led to the degradation of the classical Mes-Acr+ photocatalyst. The presence of bulky tert-butyl groups in the 3- and 6-positions provided a greater catalyst

• -butyl peroxide (40.1), generating a hydroxy radical and a tert-butoxy radical. The latter promotes an H abstraction from the substrate tetrahydrofuran (8.1), giving access to an α-oxy C(sp3) radical, which is trapped by an alkyne 40.2, providing the desired vinylation product 40.3. Sulfur-centered

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• UNLPF-12 afforded the Mannich products in 87–98% yields (Scheme 63) [40]. As previously shown (Scheme 50), the oxidation of amines to imines by singlet oxygen furnishes hydrogen peroxide as a byproduct. In 2014, Seeberger and co-workers used this byproduct, in a continuous-flow approach, as an

Combining enyne metathesis with long-established organic transformations: a powerful strategy for the sustainable synthesis of bioactive molecules

• Valerian Dragutan,
• Ileana Dragutan,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2020, 16, 738–755, doi:10.3762/bjoc.16.68

• peroxide bridge, has been subject of extensive scientific investigations during the last decade [53][54][55][56][57][58][59][60][61][62][63]. In this context, Seeberger and co-workers successfully developed an ingenious continuous-flow process for the hemisynthesis of pure artemisinin from

• peroxide groups in the corresponding artemisinin analog was eventually achieved by applying further oxidation. In a similar way to the above Oguri protocol, Li et al. prepared nanolobatolide (2), a potent neuroprotective agent, by successfully applying a tandem ring-closing metathesis of dienynes and

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• products (Scheme 26). From the different radical generators screened, dicumyl peroxide (DCP) was found to be very effective in leading to the corresponding products 144–148. Along with different acrylamides, different hydrosilanes were used as silyl source and the reaction could be applied to a wide

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• carbon dioxide and phenyllithium gives the phosphine ferrocene carboxylic acid 152 as the major reagent. Oxidation of the phosphine using hydrogen peroxide generated the phosphine oxide 153. In situ chlorination of the carboxylic acid followed by addition of the chiral amino alcohols gave the phosphoryl

Why do thioureas and squaramides slow down the Ireland–Claisen rearrangement?

• Dominika Krištofíková,
• Juraj Filo,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2019, 15, 2948–2957, doi:10.3762/bjoc.15.290

• rearrangement proceeded in 2-MeTHF with slightly lower yield and very similar diastereoselectivity as in DCM (Table 5, entries 1 and 2). A low tendency to peroxide formation, stability under acidic and basic conditions, high boiling point, and low heat of vaporization are also positive features of cyclopentyl

Chiral terpene auxiliaries V: Synthesis of new chiral γ-hydroxyphosphine oxides derived from α-pinene

• Anna Kmieciak and
• Marek P. Krzemiński

Beilstein J. Org. Chem. 2019, 15, 2493–2499, doi:10.3762/bjoc.15.242

• % yield) allowed to upgrade the enantiomeric purity of dIpc2BH [25]. Oxidation of the resulting dialkylborane with hydrogen peroxide provided enantiomerically pure (−)-isopinocampheol (7) in 78% yield. The Brown–Garg protocol [26] was employed to oxidize 7 with an aqueous solution of sodium dichromate and

• selenium dioxide in methanol [28]. The obtained phenyl selenide 14 was oxidized with hydrogen peroxide in the presence of pyridine to selenoxide, which readily undergoes intramolecular syn-elimination to produce α,β-unsaturated (+)-apoverbenone (15) [28][29]. In the next step, Luche reduction of 15

• sodium hydroxide (2.7 mL, 8.1 mmol) were carefully added. After cooling to 0 °C, a 30% solution of hydrogen peroxide (1.2 mL, 12 mmol) was added dropwise to the reaction mixture. The solution was stirred for 30 minutes at rt and 1 h at 50 °C. After this time, potassium carbonate was added to saturate the

Functionalization of 4-bromobenzo[c][2,7]naphthyridine via regioselective direct ring metalation. A novel approach to analogues of pyridoacridine alkaloids

• Benedikt C. Melzer,
• Alois Plodek and
• Franz Bracher

Beilstein J. Org. Chem. 2019, 15, 2304–2310, doi:10.3762/bjoc.15.222

• [12]. Our group demonstrated that nucleophilic radicals (1,3,5-trioxanyl, ethoxycarbonyl, methyl [14], but not benzoyl [15]) generated with peroxide under Minisci conditions, readily add to C-5 of 4-bromo- (9d) and 4-acetylbenzo[c][2,7]naphthyridine (9e) to give 5-substituted-5,6-dihydro derivatives

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

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

• singlet state oxygen to form similar peroxide, epoxide or epidioxide [16] derivatives, which can be isolated at room temperature (Scheme 4). An interesting physical characteristic of pentafulvene derivatives is their bright colour, which results from their cross conjugation, and varies with substitution

α-Photooxygenation of chiral aldehydes with singlet oxygen

• Dominika J. Walaszek,
• Magdalena Jawiczuk,
• Jakub Durka,
• Olga Drapała and
• Dorota Gryko

Beilstein J. Org. Chem. 2019, 15, 2076–2084, doi:10.3762/bjoc.15.205

• ], TEMPO [4], or benzoyl peroxide [5][6][7][8]. Therefore, the use of environmentally friendly reagents instead is highly desirable. Along this line, singlet oxygen by being easily photochemically generated from triplet oxygen in the presence of organic dyes seems promising. Despite its high reactivity and

A review of the total syntheses of triptolide

• Xiang Zhang,
• Zaozao Xiao and
• Hongtao Xu

Beilstein J. Org. Chem. 2019, 15, 1984–1995, doi:10.3762/bjoc.15.194

• the desired stereochemistry of the C-7 benzylic hydroxy group. Compound 46 was converted to triptonide 2 by Alder periodate reaction (NaIO4, 74%), and a sequencing m-CPBA epoxidation and basic hydrogen peroxide oxidation (H2O2/OH−) procedure (two steps, 28%). Finally, sodium borohydride reduction of 2

Insertion of [1.1.1]propellane into aromatic disulfides

• Robin M. Bär,
• Gregor Heinrich,
• Martin Nieger,
• Olaf Fuhr and
• Stefan Bräse

Beilstein J. Org. Chem. 2019, 15, 1172–1180, doi:10.3762/bjoc.15.114

• internal standard was added. In the dark, no conversion could be observed at all. The exposure to daylight led to a conversion of less than 10% after 1 h. With a 500 W halogen lamp, 90% of the starting material was consumed after 1 h. By the addition of di-tert-butyl peroxide (DTBP) as a radical initiator

• peroxide, DTBP) led to increased amounts of insoluble polymer. Molecular structure of 6a (displacement parameters are drawn at 50% probability level), distance C1–C3 1.844(3) Å. NMR spectra of pure 6a (green) and 6d (red) and the obtained mixture with the new compound 15 (blue). Summary of the most recent

Stereo- and regioselective hydroboration of 1-exo-methylene pyranoses: discovery of aryltriazolylmethyl C-galactopyranosides as selective galectin-1 inhibitors

• Alexander Dahlqvist,
• Axel Furevi,
• Niklas Warlin,
• Hakon Leffler and
• Ulf J. Nilsson

Beilstein J. Org. Chem. 2019, 15, 1046–1060, doi:10.3762/bjoc.15.102

• route to 2-deoxyhepuloses 3, 5 and 7 [27][28][29][30]. The hydroboration of enol ethers 2, 4, and 6 with borane dimethyl sulfide in THF, followed by oxidation using hydrogen peroxide and sodium hydroxide gave 2-deoxygalactoheptulose 3 and 2-deoxymannoheptulose 5 in good yields (89% and 78%) and with

• , 14.00 mmol, 1 M) and hydrogen peroxide (33%, 2 mL, 20.5 mmol) were added, and the reaction mixture left for 2 h. Upon completion of the reaction, 1 M hydrochloric acid was added to the reaction mixture until the pH was approximately 7. The reaction mixture was poured into brine (150 mL), extracted with

• observed. After completion of the gas evolution, sodium hydroxide (131 µL, 0.131 mmol, 1 M) and hydrogen peroxide (33%, 13 µL, 0.131 mmol) were added, and the reaction mixture left for 2 h. Upon completion of the reaction, 1 M hydrochloric acid was added to the reaction mixture until the pH was

Towards the preparation of synthetic outer membrane vesicle models with micromolar affinity to wheat germ agglutinin using a dialkyl thioglycoside

• Dimitri Fayolle,
• Nathalie Berthet,
• Bastien Doumeche,
• Olivier Renaudet,
• Peter Strazewski and
• Michele Fiore

Beilstein J. Org. Chem. 2019, 15, 937–946, doi:10.3762/bjoc.15.90

• color was developed using OPD (100 μL per well, 0.4 mg mL−1 in 0.05 M phosphate-citrate buffer) and urea hydrogen peroxide (0.4 mg mL−1). The reaction was stopped after 10 min by adding H2SO4 (30% v/v, 50 μL per well) and the absorbance was measured at 490 nm. The percentage of inhibition was determined

Azologization of serotonin 5-HT₃ receptor antagonists

• Karin Rustler,
• Galyna Maleeva,
• Piotr Bregestovski and
• Burkhard König

Beilstein J. Org. Chem. 2019, 15, 780–788, doi:10.3762/bjoc.15.74

• reacted with the 2-chloroacetylacetone ester derivative 7 providing hydrazine 8 [66]. Upon reaction of the chloro-ester 8 with phenylenediamine (9) in the presence of triethylamine the quinoxaline moiety was formed [67]. Oxidation of the hydrazine derivative 10 using hydrogen peroxide under an oxygen

Synthesis of polydicyclopentadiene using the Cp₂TiCl₂/Et₂AlCl catalytic system and thin-layer oxidation of the polymer in air

• Zhargolma B. Bazarova,
• Ludmila S. Soroka,
• Alex A. Lyapkov,
• Мekhman S. Yusubov and
• Francis Verpoort

Beilstein J. Org. Chem. 2019, 15, 733–745, doi:10.3762/bjoc.15.69

• time of a layer in air at ambient temperature (Figure 13). According to the classical theory of oxidation of polymers, the formation of primary radicals occurs predominantly, and only when they are formed, further oxidation of the -C=C- bonds occurs with the aid of the peroxide radicals formed. However

• adsorption of oxygen and its transport through the polymer layer becomes the slowest process, which leads to a change in shape of the kinetic curve of the accumulation of peroxide radicals (Figure 13). The curve in Figure 13 averages the experimental points of the oxidation process and is a result of two

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• hexachloroacetone [28][71] or cobalt(II) acetate in the presence of hydrogen peroxide followed by removal of the cobalt cations with QuadraSil AP resin [60]. The nature of the counter anion vary as a function of the conditions applied. Reduction of N1-substituted 3-nicotinamide salts to the corresponding 1,4

• cobalt acetate in the presence of hydrogen peroxide. This approach required the subsequent removal of metal ions by Quadrasil resin. The oxidized acetonides 45 were subsequently deprotected using

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• and aldehydes 48 to provide 2-acyl-3,4-dihydronaphthalenes 49 in moderate to excellent yields via a series of radical addition, ring-opening and cyclization in the presence of DTBP (di-tert-butyl peroxide) and Lewis acids (Scheme 12) [73]. Moreover, the experimental results showed MCPs 1 with electron

Catalysis of linear alkene metathesis by Grubbs-type ruthenium alkylidene complexes containing hemilabile α,α-diphenyl-(monosubstituted-pyridin-2-yl)methanolato ligands

• Tegene T. Tole,
• Johan H. L. Jordaan and
• Hermanus C. M. Vosloo

Beilstein J. Org. Chem. 2019, 15, 194–209, doi:10.3762/bjoc.15.19

• %), 1-octene (99% GC), nonane (reagent plus 99%) and toluene (99%) were purchased from Sigma-Aldrich. Toluene-d8 (99.5%) was purchased from MERCK and tert-butyl hydrogen peroxide (80%) from Riedel-de Haen. Diethyl ether and THF were dried over Na in the presence of benzophenone. Pentane was distilled

• min with a gastight syringe (1 mL), transferred to a GC vial (1 mL), quenched with toluene (0.3 mL) and tert-butyl hydrogen peroxide (2 drops), and then injected into a GC/FID by auto sampler. The metathesis reaction was terminated after 1440 minutes and analysed by GC/FID. Some samples were also