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

• reagents has been reported by Kluver et al. [54], by which the product was isolated in excellent yield (71%). It was noted that the magnesium ions increase the water partition coefficient of these compounds since they coordinate stronger to the nitrogen atoms as compared to lithium ions. In this case

• magnesium-containing triazoles 66 which, upon quenching with ammonium chloride, afforded the triazoles 67. Lithiation followed by coupling with the appropriate chlorophosphines resulted in the desired 1,5-disubstitued triazolylphosphine ligands 68. The procedure could be performed in one pot by directly

• deprotection then furnished 83b in reasonable yields between 68 and 87%. Bis(diphenylphosphine)-substituted imidazoles were also synthesized by Karthik et al. [87] starting from the diiodoimidazole derivative 84. The lithium chloride mediated magnesium/iodine exchange reaction of 84 followed by the addition of

Formal preparation of regioregular and alternating thiophene–thiophene copolymers bearing different substituents

• Atsunori Mori,
• Keisuke Fujita,
• Chihiro Kubota,
• Toyoko Suzuki,
• Kentaro Okano,
• Takuya Matsumoto,
• Takashi Nishino and
• Masaki Horie

Beilstein J. Org. Chem. 2020, 16, 317–324, doi:10.3762/bjoc.16.31

• to afford the regioregular polythiophene in which 2,5-dihalo-3-substituted thiophene 1 is employed as a monomer precursor, converting to the corresponding organometallic monomer by a halogen−magnesium exchange reaction with a Grignard reagent. The employment of 1 leading to polythiophene has been

• shown to proceed in a dehalogenative manner [3]. We have recently shown that the generation of the organometallic monomer species can alternatively also be achieved by deprotonation, using 2-halo-3-substituted thiophene 2 or 3 with a bulky magnesium amide Knochel–Hauser base (TMPMgCl⋅LiCl) [7], followed

Understanding the role of active site residues in CotB2 catalysis using a cluster model

• Keren Raz,
• Ronja Driller,
• Thomas Brück,
• Bernhard Loll and
• Dan T. Major

Beilstein J. Org. Chem. 2020, 16, 50–59, doi:10.3762/bjoc.16.7

• reaction. The coordinates of the amino acids and the substrate GGPP were taken from the corresponding X-ray structure, with a resolution of 1.8 Å [42]. In this approach, geometry optimizations with the “Modredundant” keyword were performed, and the active site residues, diphosphate moiety, and magnesium

Palladium-catalyzed synthesis and nucleotide pyrophosphatase inhibition of benzo[4,5]furo[3,2-b]indoles

• Hoang Huy Do,
• Saif Ullah,
• Alexander Villinger,
• Joanna Lecka,
• Jean Sévigny,
• Peter Ehlers,
• Jamshed Iqbal and
• Peter Langer

Beilstein J. Org. Chem. 2019, 15, 2830–2839, doi:10.3762/bjoc.15.276

• considering an already reported colorimetric method with minor modifications [38][39][40][41]. The reaction buffer was comprised of 50 mM Tris-hydrochloric acid, 5 mM magnesium chloride (MgCl2) and 0.1 mM zinc chloride (ZnCl2) with final pH 9.5. For initial screening of compounds, first enzyme and substrate

Acid-catalyzed rearrangements in arenes: interconversions in the quaterphenyl series

• Sarah L. Skraba-Joiner,
• Carter J. Holt and
• Richard P. Johnson

Beilstein J. Org. Chem. 2019, 15, 2655–2663, doi:10.3762/bjoc.15.258

• , 3H). Synthesis of o,o’-quaterphenyl (17) [36]: A solution of 2-bromobiphenyl (0.15 g, 0.65 mmol), magnesium turnings (0.02 g, 0.69 mmol), and THF (2 mL) was stirred at ambient temperature overnight under a nitrogen atmosphere. Additional THF (4 mL) was added and the reaction mixture was cooled to −78

A new approach to silicon rhodamines by Suzuki–Miyaura coupling – scope and limitations

• Thines Kanagasundaram,
• Antje Timmermann,
• Carsten S. Kramer and
• Klaus Kopka

Beilstein J. Org. Chem. 2019, 15, 2569–2576, doi:10.3762/bjoc.15.250

• added the double Grignard reagent 4 to methyl esters 5 [26]. A similar approach was established by Lavis, herein electrophiles (anhydrides or esters) were added to lithium or magnesium organyls 4 [27]. Johnsson and co-workers could establish dye formation by addition of aryllithium 7 to the silicon

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

• added dropwise. After 3 h, the mixture was filtered, 10% sodium metabisulphite (15 mL) was added to the filtrate, and the mixture was stirred for 10 min. The layers were separated, the organic layer was washed with 1 M NaOH (2 × 15 mL), brine (10 mL), and dried over anhydrous magnesium sulfate. The

• solution. The layers were separated and the aqueous layer was extracted with diethyl ether (2 × 20 mL). The combined organic layers were washed with brine (15 mL), dried with anhydrous magnesium sulfate, filtered and the solvents were removed using a rotary evaporator. The product was purified by column

• brine (5 mL). After drying the solution with anhydrous magnesium sulfate and filtration, the solvent was evaporated and the product was purified by flash chromatography on silica gel (hexane/ethyl acetate 80:20). Phosphine 23 (0.131 g, 62%) was obtained as a colorless oil. 1H NMR (700 MHz, CDCl3) δ 0.93

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

• bromo substituent of the appropriate substrates 20a or 20b should converted into the respective organomagnesium product by bromine–magnesium exchange. In an expected subsequent Parham-type ring-closing reaction [33] the nucleophilic carbon at position 4 should trap the ester (or nitrile) group to lead

• . Reaction of 20a with 2.2 equiv iPrMgCl∙LiCl, which is a very mild reagent for bromine–magnesium exchange reactions in the presence of labile functional groups like esters [35], at 0 °C led, after aqueous work-up, to the formation of the expected pyridoacridone 22 in 28% yield (Scheme 5). Although starting

• material could not be recovered, another product 23, which is most likely the debrominated, not cyclized analogue of 20a, was observed in traces. The outcome of this experiment shows that the bromine–magnesium exchange reaction was most likely completed, but the intramolecular trapping of the ester group

1,2,3,4-Tetrahydro-1,4,5,8-tetraazaanthracene revisited: properties and structural evidence of aromaticity loss

• Arnault Heynderickx,
• Sébastien Nénon,
• Olivier Siri,
• Vladimir Lokshin and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2019, 15, 2059–2068, doi:10.3762/bjoc.15.203

• ). The extracts were dried over magnesium sulfate and concentrated in vacuo. The residue was purified by column chromatography on silica gel using CH2Cl2/AcOEt/MeOH (8:2:1) as eluent, to give the titled product (696 mg, 96%) as colorless solid. Mp: 232 °C (244 °C [8]); 1H NMR (CDCl3) δ 2.37 (s, 6H), 4.05

• , the solvents were evaporated in vacuo and the residue was dissolved in dichloromethane (50 mL). The organic layer was washed with an aqueous sodium hydroxide (1 M, 2 × 5 mL), then with water (10 mL), dried over magnesium sulfate, evaporated. The crude product was purified by column chromatography on

• hydroxide (1 M, 2 × 5 mL), then with water (10 mL), dried over magnesium sulfate, and evaporated. The crude product was purified by column chromatography on silica gel using cyclohexane/AcOEt (3:7) to furnish the titled product in 48% yield (348 mg) as a yellow solid. 1H NMR (CDCl3) δ 1.38 (s, 9H), 3.67 (t

Functional panchromatic BODIPY dyes with near-infrared absorption: design, synthesis, characterization and use in dye-sensitized solar cells

• Quentin Huaulmé,
• Cyril Aumaitre,
• Outi Vilhelmiina Kontkanen,
• David Beljonne,
• Alexandra Sutter,
• Gilles Ulrich,
• Renaud Demadrille and
• Nicolas Leclerc

Beilstein J. Org. Chem. 2019, 15, 1758–1768, doi:10.3762/bjoc.15.169

• %, 6: 30%; d) (3-(2-methoxyethoxy)prop-1-yn-1-yl)magnesium bromide, THF, 60 °C, 85%; e) carbon monoxide, sodium formiate, [Pd(PPh3)2Cl2], anhydrous DMF, 100 °C, 8: 19%, 9: 35%; f) cyanoacetic acid, piperidine, MeCN, CHCl3, 80 °C, BOD-TTPA: 34%, BOD-TTPA-alk: 26%. a) Absorption spectra of compounds BOD

Anomeric sugar boronic acid analogues as potential agents for boron neutron capture therapy

• Daniela Imperio,
• Erika Del Grosso,
• Silvia Fallarini,
• Grazia Lombardi and
• Luigi Panza

Beilstein J. Org. Chem. 2019, 15, 1355–1359, doi:10.3762/bjoc.15.135

• conversion into trifluoroborates [10]. In principle, the best way to obtain anomeric boron analogues mimicking hexoses would be the addition of a nucleophilic boron reagent on a properly protected pentose. Actually, boryllithium and magnesium reagents [11][12][13][14] have been described but, after a careful

An improved synthesis of adefovir and related analogues

• David J. Jones,
• Eileen M. O’Leary and
• Timothy P. O’Sullivan

Beilstein J. Org. Chem. 2019, 15, 801–810, doi:10.3762/bjoc.15.77

• Sciences, Cork Institute of Technology, Cork, Ireland 10.3762/bjoc.15.77 Abstract An improved synthesis of the antiviral drug adefovir is presented. Problems associated with current routes to adefovir include capricious yields and a reliance on problematic reagents and solvents, such as magnesium tert

• studies [35][37][38][39]. While it was demonstrated that magnesium tert-butoxide (MTB) is the optimum base for this transformation (Scheme 1), it is not without drawbacks. MTB is expensive and hydrolyses on storage when exposed to moisture. The yield for the reaction is often inconsistent, being highly

• dependent on the quality of the MTB employed. The reaction does not proceed to completion when a stoichiometric amount of the base is used and up to 3.0 equivalents may be required in order to ensure complete consumption of the starting alcohol. The resultant magnesium salts are highly deliquescent and form

Synthesis of the aglycon of scorzodihydrostilbenes B and D

• Katja Weimann and
• Manfred Braun

Beilstein J. Org. Chem. 2019, 15, 610–616, doi:10.3762/bjoc.15.56

• brine and dried with magnesium sulfate. The solvent was removed in a rotary evaporator and the crude product (1.08 g) was purified by column chromatography (silica gel; ethyl acetate/n-hexane, 1:4 to 1:2) to give 91 mg (14%) of pure glycoside 12 as a colorless syrup. 1H NMR (CDCl3, 600 MHz) δ 2.04 (s

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

• order to manipulate the NAD+ pathway in mammalian cells and tissues. The key step in the synthesis of the NMN analogues 39–41 is the activation of the 5′-hydroxy group of the NRH acetonide 42 with a Grignard reagent, to produce the corresponding magnesium alkoxide. As illustrated by the synthesis of the

Study on the regioselectivity of the N-ethylation reaction of N-benzyl-4-oxo-1,4-dihydroquinoline-3-carboxamide

• Pedro N. Batalha,
• Luana da S. M. Forezi,
• Maria Clara R. Freitas,
• Nathalia M. de C. Tolentino,
• Ednilsom Orestes,
• José Walkimar de M. Carneiro,
• Fernanda da C. S. Boechat and
• Maria Cecília B. V. de Souza

Beilstein J. Org. Chem. 2019, 15, 388–400, doi:10.3762/bjoc.15.35

• carboxamide group, may contribute to enhance the bioactivity. This fact could be explained by the coplanarity induced by the C-4 carbonyl hydrogen bond interactions with biological targets [3] or complexation with physiological metal cations such as magnesium and zinc [23]. Besides the derivatives 3a and 3b

Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels–Alder reaction with inverse electron demand

• Anne Schnell,
• J. Alexander Willms,
• S. Nozinovic and
• Marianne Engeser

Beilstein J. Org. Chem. 2019, 15, 30–43, doi:10.3762/bjoc.15.3

• organic layer was washed with brine and dried over magnesium sulfate. The solvents were evaporated and the remaining solid was dissolved in 4.4 mL acetic acid at 0 °C. The mixture was stirred while a solution of sodium nitrite (839 mg, 12.17 mmol, 7.4 equiv) in 1 mL of deionized water was added dropwise

• . The mixture was stirred for another 3 h, after the solution of sodium nitrite had been added. 55 mL dichloromethane were added and the organic layer was washed twice with saturated sodium hydrogen carbonate solution and dried over magnesium sulfate. The solvents were evaporated and 340 mg of a pink

Thermophilic phosphoribosyltransferases Thermus thermophilus HB27 in nucleotide synthesis

• Ilja V. Fateev,
• Ekaterina V. Sinitsina,
• Aiguzel U. Bikanasova,
• Maria A. Kostromina,
• Elena S. Tuzova,
• Larisa V. Esipova,
• Tatiana I. Muravyova,
• Alexei L. Kayushin,
• Irina D. Konstantinova and
• Roman S. Esipov

Beilstein J. Org. Chem. 2018, 14, 3098–3105, doi:10.3762/bjoc.14.289

• (1.1 unit/mg) is observed at 60 °C. The activity at 36 °C is 5% from the maximal one and at 90 °C it is 3% from the maximal one. It is interesting, that TthAPRT shows its maximal activity at 75 °C. The influence of the magnesium ion concentration on the TthHPRT activity is nonlinear. The activity

• increases rapidly while the magnesium chloride concentration increases from 0 to 1 mM (Figure 4). Further increasing of the concentration (up to 5 mM) does not increase the activity significantly. Since the reaction rate increases rapidly with increasing the magnesium chloride concentration to values

• equivalent to the concentration of 5-phosphoribosyl-α-1-pyrophosphate (1 mM), it can be assumed that the presence of magnesium ions promotes the proper spatial orientation of the substrate. The reaction also proceeds in the absence of magnesium ions in solution. A similar dependence is observed for TthAPRT

Nucleofugal behavior of a β-shielded α-cyanovinyl carbanion

• Rudolf Knorr and
• Barbara Schmidt

Beilstein J. Org. Chem. 2018, 14, 3018–3024, doi:10.3762/bjoc.14.281

• °C; the subsequent cleavage reaction of the generated magnesium alkoxide 14b was very slow at rt, creating 2MgBr (Scheme 3) in the presence of t-BuCH=O (4) and therefrom 7 together with only a small amount of 1. This almost clean production of 7 agrees with the versatile [5] reactions of H2C=C(CN

• ; this provided a first evidence for the retro-addition process with an alkenylmetal intermediate. These fissions were slow in case of the magnesium alkoxide but rapid for the lithium or potassium alkoxides at ambient temperatures. (iii) The alternative trapping [3] of the carbonyl component by means of

Domino ring-opening–ring-closing enyne metathesis vs enyne metathesis of norbornene derivatives with alkynyl side chains. Construction of condensed polycarbocycles

• Ritabrata Datta and
• Subrata Ghosh

Beilstein J. Org. Chem. 2018, 14, 2708–2714, doi:10.3762/bjoc.14.248

• (G-II) was used. The norbornene derivative 7a was first chosen for investigating ROM–RCEYM. Compound 7a was prepared in the following way (Scheme 3). Reaction of the known lactol 5 [33] with propargyl magnesium bromide afforded the diol 6 in 88% yield (For detailed experimental procedures and

Microwave-assisted synthesis of biologically relevant steroidal 17-exo-pyrazol-5'-ones from a norpregnene precursor by a side-chain elongation/heterocyclization sequence

• Gergő Mótyán,
• László Mérai,
• Márton Attila Kiss,
• Zsuzsanna Schelz,
• Izabella Sinka,
• István Zupkó and
• Éva Frank

Beilstein J. Org. Chem. 2018, 14, 2589–2596, doi:10.3762/bjoc.14.236

• magnesium enolate of malonic acid half ester, prepared in situ from potassium methyl malonate, MgCl2 and triethylamine in acetonitrile, was added [24][25]. The acylation of magnesium methyl malonate by the preformed imidazole 3 led to the desired bifunctional starting material 4 in good yield (79

• magnesium enolate. Although the presence of a C16–C17 double bond as in 4' is assumed to be beneficial for a P45017α-inhibitory effect, further transformations of this compound were abandoned because of the insufficient yield and its potential tendency to react with monosubstituted hydrazines – not only

Practical tetrafluoroethylene fragment installation through a coupling reaction of (1,1,2,2-tetrafluorobut-3-en-1-yl)zinc bromide with various electrophiles

• Ken Tamamoto,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2018, 14, 2375–2383, doi:10.3762/bjoc.14.213

• that possesses higher thermal stability than the corresponding organolithium or -magnesium species due to the almost covalent C–Zn bond [29][30]. Moreover, organozinc reagents can be easily transformed to the “reactive” species, through a transmetallation process with a transition metal (e.g., Pd or Cu

• tetrafluoroethyllithium [12][25] and -magnesium species [22][23]. The synthetic uses of 2-Zn as a promising tetrafluorinating agent were tested in several reactions. First, we demonstrated a typical C–C bond formation reaction. Treating freshly prepared 2-Zn (ca. 0.70 M in DMF) with 5.0 equiv of iodobenzene (3a) in the

Novel photochemical reactions of carbocyclic diazodiketones without elimination of nitrogen – a suitable way to N-hydrazonation of C–H-bonds

• Liudmila L. Rodina,
• Xenia V. Azarova,
• Jury J. Medvedev,
• Dmitrij V. Semenok and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2018, 14, 2250–2258, doi:10.3762/bjoc.14.200

• for up to 6.5 h (control of the reacted diazodiketone 1 by TLC). Thereupon the reaction mixture was dried over magnesium sulfate, the solvent completely distilled off in vacuum and the residue separated by column chromatography (SiO2, eluent: petroleum ether → petroleum ether/acetone 8:1) to give the

• disappearance of diazodiketone 1a (control by TLC). Then the reaction mixture was dried with magnesium sulfate and the solvent distilled off in vacuum. The obtained residue was dissolved in 25 ml of anhydrous Et2O, cooled to −75 to −78 °C. The precipitated resinous matter was separated by decantation and the

• glutaric acid. Photolysis of diazodiketone 1b (with MeOH). A solution of diazodiketone 1b (141 mg, 0.75 mmol) in 10 ml of THF/CH3OH 200:1 was irradiated for 55 min in a quartz reactor (λ > 210 nm). Then the reaction mixture was dried with magnesium sulfate and the solvent and excess of CH3OH were

Studies towards the synthesis of hyperireflexolide A

• G. Hari Mangeswara Rao

Beilstein J. Org. Chem. 2018, 14, 2106–2111, doi:10.3762/bjoc.14.185

• dichloroethane (1,2-DCE) were distilled over phosphorous pentoxide and stored over 4 Å molecular sieves. Acetone was distilled over anhydrous K2CO3. Methanol was refluxed and distilled over magnesium turnings and stored over 4 Å molecular sieves. Distilled water was used for aqueous reactions and aqueous work-up

Oligonucleotide analogues with cationic backbone linkages

• Melissa Meng and
• Christian Ducho

Beilstein J. Org. Chem. 2018, 14, 1293–1308, doi:10.3762/bjoc.14.111

• ≈25 °C for the according hybridization with DNA was observed [40]. In addition, the cationic dimer 11 was shown to bind more tightly to native RNA and DNA strands in the presence of magnesium chloride [40]. For the cationic T-oligomer 18, Letsinger and co-workers reported a strongly reduced absorbance

Rhodium-catalyzed C–H functionalization of heteroarenes using indoleBX hypervalent iodine reagents

• Erwann Grenet,
• Ashis Das,
• Paola Caramenti and
• Jérôme Waser

Beilstein J. Org. Chem. 2018, 14, 1208–1214, doi:10.3762/bjoc.14.102

• separated and the aqueous layer was extracted twice with DCM (5 mL). The organic layers were combined, dried over magnesium sulfate dehydrate, filtered and concentrated under reduced pressure. The crude residue was purified by preparative TLC using DCM/MeOH to afford the pure desired compound. Bioactive