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

• sodium carbonate to give (+)-3-methyleneverbanone (5) in 57% yield from 3. α,β-Unsaturated ketone 5 was exclusively reduced to allylic alcohol (1R,2R,4S,5R)-3-methyleneneoisoverbanol (6), using the Luche method [24]. 1,2-Reduction of enone 5 was achieved with sodium borohydride in the presence of cerium

• 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

• cross-coupling reactions, 4-bromo-5 iodobenzo[c][2,7]naphthyridine (13) is regarded as an interesting building block for synthetic chemists. Another interesting building block is ester 14, which was obtained in 37% yield by quenching 5-metalated 9d with diethyl carbonate. The quenching of 9d after

Regioselective Pd-catalyzed direct C1- and C2-arylations of lilolidine for the access to 5,6-dihydropyrrolo[3,2,1-ij]quinoline derivatives

• Hai-Yun Huang,
• Haoran Li,
• Thierry Roisnel,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2019, 15, 2069–2075, doi:10.3762/bjoc.15.204

• % affording 1a in 83% yield. The use of KOAc associated to PdCl(C3H5)(dppb) catalyst also afforded the regioisomer 1a in a quite good regioselectivity and yield (Table 1, entry 11). The higher conversions observed in the presence of acetate bases compared to carbonate bases (Table 1, entries 4–6 and 8–11

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

• was stirred at reflux for 48 h. After cooling, the excess of acetic anhydride was evaporated under reduced pressure. The residue was triturated with dichloromethane (20 mL) and H2O (20 mL). The aqueous layer was neutralized by adding solid sodium carbonate and extracted with dichloromethane (2 × 20 mL

Synthesis of benzo[d]imidazo[2,1-b]benzoselenoazoles: Cs₂CO₃-mediated cyclization of 1-(2-bromoaryl)benzimidazoles with selenium

• Mio Matsumura,
• Yuki Kitamura,
• Arisa Yamauchi,
• Yoshitaka Kanazawa,
• Yuki Murata,
• Tadashi Hyodo,
• Kentaro Yamaguchi and
• Shuji Yasuike

Beilstein J. Org. Chem. 2019, 15, 2029–2035, doi:10.3762/bjoc.15.199

• . Keywords: benzimidazole; cesium carbonate; cyclization; selenium; selenoazole; Introduction Selenium-containing heterocyclic ring systems have attracted attention not only because of their chemical properties and reactivities, but also for their wide biological activities [1][2][3][4]. For example

• . Experimental General procedure for the synthesis of benzoimidazo[2,1-b]benzoselenoazoles: 1-(2-Bromoaryl)benzimidazoles 1 (0.5 mmol), selenium powder (79 mg, 1.0 mmol, 2 equiv), and cesium carbonate (326 mg, 1.0 mmol, 2 equiv) were dissolved in DMF (1 mL) under Ar atmosphere. The mixture was stirred at 150 °C

Design, synthesis and biological evaluation of immunostimulating mannosylated desmuramyl peptides

• Rosana Ribić,
• Ranko Stojković,
• Lidija Milković,
• Mariastefania Antica,
• Marko Cigler and
• Srđanka Tomić

Beilstein J. Org. Chem. 2019, 15, 1805–1814, doi:10.3762/bjoc.15.174

• substitution of bromine from tert-butyl bromoacetate with 2,3,4,6-tetra-O-acetyl-α-ᴅ-mannopyranose (9) in the presence of potassium carbonate followed. Chemoselective removal of the tert-butyl ester group from compound 10 resulted with O-mannoside 11 with a free carboxy group available for coupling of the

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• hydrogenation followed by saponification converted 178 into (2S,3S)-N-Boc-3-hydroxy-2-hydroxymethylpyrrolidine (2S,3S)-179, one of the simplest members of the iminosugar family. Reaction of aziridine 4-methoxyphenyl esters either (2R,1′S)-5e or (2S,1′S)-5e with vinylene carbonate at 280 °C gave a mixture of

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• carbonate as a base under aerobic conditions. Along with the synthesis of pyrido[1,2-a]benzimidazoles 78, they have reported the synthesis of benzimidazo[1,2-a]quinoline 79 and benzimidazo[1,2-a]isoquinoline 80 in good to excellent yields. They have used differently substituted arylboronic acids 77 as one

Synthesis of ([1,2,4]triazolo[4,3-a]pyridin-3-ylmethyl)phosphonates and their benzo derivatives via 5-exo-dig cyclization

• Aleksandr S. Krylov,
• Artem A. Petrosian,
• Julia L. Piterskaya,
• Nataly I. Svintsitskaya and
• Albina V. Dogadina

Beilstein J. Org. Chem. 2019, 15, 1563–1568, doi:10.3762/bjoc.15.159

• ring of the starting 2-hydrazinylpyridines 1i and 1j significantly violates the reaction selectivity, leading to a rapid resinification of the reaction mixture. However, the exclusion of potassium carbonate allows the reaction to proceed selectively within 150 hours at a temperature of 60 °C. The

• . The ease of the formation of isomers 11 in this case and 12 in other similar synthesis, is caused not only by the presence of a nitro group in the pyridine ring, but also by the presence of hydrogen chloride, which is eliminated by potassium carbonate in the former experiments (Scheme 2). The acid

An azobenzene container showing a definite folding – synthesis and structural investigation

• Abdulselam Adam,
• Saber Mehrparvar and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2019, 15, 1534–1544, doi:10.3762/bjoc.15.156

• strategy and we tried to synthesize the chiral foldable container 10 in a one pot reaction. For this purpose, the platforms 2a and 3a and the dibromide 9 were dissolved in acetonitrile in the ratio 1:1:2.2. To this solution potassium carbonate as base was added and the whole mixture was refluxed for one

• , 0.391 mmol) in acetonitrile (225 mL), potassium carbonate (491 mg, 3.554 mmol) was added and the mixture was refluxed at 85 °C for 25 h under an argon atmosphere. After cooling to room temperature, the solvent was evaporated to dryness, the residue was dissolved in DCM and washed with water. The aqueous

A novel three-component reaction between isocyanides, alcohols or thiols and elemental sulfur: a mild, catalyst-free approach towards O-thiocarbamates and dithiocarbamates

• András György Németh,
• György Miklós Keserű and
• Péter Ábrányi-Balogh

Beilstein J. Org. Chem. 2019, 15, 1523–1533, doi:10.3762/bjoc.15.155

• isocyanide component under air. In the case of using other bases, such as caesium carbonate (Cs2CO3), diisopropylethylamine (DIPEA) or sodium ethoxide (NaOEt), only the isothiocyanate intermediate of the reaction was isolated (Table 1, entries 17, 18, and 20). However, using diazabicycloundecene (DBU) as the

Synthesis of aryl cyclopropyl sulfides through copper-promoted S-cyclopropylation of thiophenols using cyclopropylboronic acid

• Emeline Benoit,
• Ahmed Fnaiche and
• Alexandre Gagnon

Beilstein J. Org. Chem. 2019, 15, 1162–1171, doi:10.3762/bjoc.15.113

• equivalent of copper(II) acetate, 1.0 equivalent of bipyridine, and 2.0 equivalents of sodium carbonate in dichloroethane at 70 °C for 16 hours provided the desired S-cyclopropylated compound 1a in 86% yield accompanied by only 4% of the diaryl disulfide side-product 26a (Table 1, entry 1, "standard

• only viable alternative to bipyridine (Table 1, entry 7), with other ligands commonly used in copper-catalyzed reactions such as proline and 2,2,6,6-tetramethyl-3,5-heptanedione giving yields under 15%. Reducing the number of equivalents of boronic acid 25 and sodium carbonate was found to be well

• tolerated, giving a comparable yield as the "standard conditions" (Table 1, entry 8). While changing the inorganic base to potassium phosphate tribasic or potassium carbonate gave yields below 75%, we found that cesium carbonate provided a net increase in the yield of the reaction (Table 1, entry 9

Electrophilic oligodeoxynucleotide synthesis using dM-Dmoc for amino protection

• Shahien Shahsavari,
• Dhananjani N. A. M. Eriyagama,
• Bhaskar Halami,
• Vagarshak Begoyan,
• Marina Tanasova,
• Jinsen Chen and
• Shiyue Fang

Beilstein J. Org. Chem. 2019, 15, 1116–1128, doi:10.3762/bjoc.15.108

• ). Due to the steric hindrance of the side product 2 from deprotection, we found that a nucleophilic scavenger was no longer needed during deprotection, and the β-elimination step could be achieved using the non-nucleophilic weak base potassium carbonate. Results and Discussion To develop the dM-Dmoc

• the overall results of the deprotection and cleavage procedure. Removal of the oxidized dM-Dmoc protection groups and cleavage of the oxidized Dmoc linker were achieved with a solution of the weak non-nucleophilic base potassium carbonate at pH 8 at room temperature giving the fully deprotected 5

• ammonium hydroxide deprotection and cleavage conditions. We have demonstrated that the so called UltraMild deprotection and cleavage conditions involving potassium carbonate in anhydrous methanol are incompatible with α-chloroacetamide and thioester [40]. These findings are easily understandable because

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• of 9, followed by an intramolecular cyclic amide formation, would produce isoindolinone derivatives 4. Employing benzoic acids 10 ortho-substituted with iodine along with alkynylcarboxylic acids 11 and ammonium acetate (12), in the presence of caesium carbonate and copper iodide as catalyst (10%), a

• reaction of propiolic acid and aryl halides [78]. Furthermore, the authors have been able to carry out the reaction in a sequential manner starting from propiolic acid and aryl iodides in the presence of caesium carbonate and a palladium catalyst. Next, addition of 2-iodobenzoic acid and ammonium acetate

Mechanochemical synthesis of poly(trimethylene carbonate)s: an example of rate acceleration

• Sora Park and
• Jeung Gon Kim

Beilstein J. Org. Chem. 2019, 15, 963–970, doi:10.3762/bjoc.15.93

• from low reactivity. The solvent-free mechanochemical polymerization of trimethylene carbonate using the organocatalysts 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) are examined herein. The polymerizations under ball-milling conditions exhibited significant

• carbonate); Introduction Nowadays mechanochemical syntheses are widespread in many areas of chemistry [1][2][3][4]. The efficient mixing and energy input induced by mechanical motions have promoted many chemical reactions with superior efficiencies [5]. Sometimes, unexpected outcomes that cannot be

• mechanochemical ball milling. The organocatalytic polymerization of trimethylene carbonate to form aliphatic polycarbonates was found to be more efficient when using a mechanical ball-milling reaction than a solution polymerization (Scheme 1). The detailed findings are disclosed in this article. Results and

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

• microscopic observation. Enzyme-linked lectin assays: 96-well microtiter Nunc-Immuno plates (Maxi-Sorp) were coated with PAA-GlcNAc (100 μL per well, diluted from a stock solution of 5 μg mL−1 in 50 mM carbonate buffer pH 9.6) for 1 h at 37 °C. The wells were then washed with T-PBS (3 × 100 μL per well, PBS

The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives

• Tilman Lechel,
• Roopender Kumar,
• Mrinal K. Bera,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61

• -Acetoxymethyl-substituted pyrimidine derivatives offer many options for the introduction of new substituents. For example the removal of the acetyl group by treatment with potassium carbonate in methanol and oxidation with Dess–Martin periodinane (DMP) converted PM61 and PM63 into aldehydes PM69 and PM71 in

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

• trifluoride etherate (0.4 mL, 3.12 mmol) were injected by syringe. The mixture was stirred at 25 °C for 2 d. Thereafter, saturated aqueous sodium hydrogen carbonate (10 mL) was added and the mixture was extracted five times with 15 mL portions of dichloromethane. The combined organic layers were washed with

Cyclopropene derivatives of aminosugars for metabolic glycoengineering

• Jessica Hassenrück and
• Valentin Wittmann

Beilstein J. Org. Chem. 2019, 15, 584–601, doi:10.3762/bjoc.15.54

• Scheme 3. Alcohol 4 was activated with 4-nitrophenyl chloroformate, and the obtained carbonate 5 reacted with neutralized mannosamine and peracetylated as described above to give Ac4ManNCyoc(H2) in a yield of 57%. Deacetylation with N,N-ethyldimethylamine in methanol and further aldolase reaction and DMB

• for C19H27NO10, 452.1527; found, 452.1522. (2-Methylcyclopropyl)methyl (4-nitrophenyl) carbonate (5): 2-Methylcyclopropanemethanol (4, 0.57 mL, 5.81 mmol) was dissolved under nitrogen atmosphere in dry dichloromethane (80 mL) and dry pyridine (2.8 mL). The solution was cooled to 4 °C and 4-nitrophenyl

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

• rather on the respective thermodynamic stability of the dihydro derivatives. Application of the dithionite reduction to the synthesis of 2,3,5-tri-O-acetyl- and 2,3,5-tri-O-benzoyl-D-β-1,4-dihydronicotinamide ribosides [19][31][35], their tripropionate, tri-n-butyrate, triisobutyrate, triethyl carbonate

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

• treated with potassium carbonate followed by a dropwise addition of bromoethane, as the alkylating agent. This synthetic strategy provided exclusively the 1-ethylated product 7 with a good overall yield (80%, Scheme 1). Previous treatment of 5 with potassium carbonate promotes the establishment of an acid

• for the deprotonation reaction using potassium carbonate as a base. These results are in agreement with the analysis of the stability of the conjugate bases due to structural electronic effects. The oxoquinoline conjugate base presents a great stability, since it promotes a greater dispersion of the

• . Procedure for the preparation of N-benzyl-1-ethyl-4-oxo-1,4-dihydroquinoline-3-carboxamide (7) In a round bottom flask, 1.0 g (3,6 mmol) of N-benzyl-4-oxo-1,4-dihydroquinoline-3-carboxamide (5), 1.4 g (10.1 mmol) of potassium carbonate and 10.0 mL of dimethyl sulfoxide (DMSO) were added and stirred at room

Chemical structure of cichorinotoxin, a cyclic lipodepsipeptide that is produced by Pseudomonas cichorii and causes varnish spots on lettuce

• Hidekazu Komatsu,
• Takashi Shirakawa,
• Takeo Uchiyama and
• Tsutomu Hoshino

Beilstein J. Org. Chem. 2019, 15, 299–309, doi:10.3762/bjoc.15.27

• : 181–184 °C. Preparation of the monoacetate and the tetraacetate This toxin (6.0 mg) was dissolved in 5 mL of a mixture (1:1) of CH3CN and 0.01 M carbonate buffer solution (pH 9.7), and then 1.5 mL of Ac2O was added. The reaction was carried out at room temperature for 6 h. Almost all of the toxin had

Olefin metathesis in multiblock copolymer synthesis

• Maria L. Gringolts,
• Yulia I. Denisova,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2019, 15, 218–235, doi:10.3762/bjoc.15.21

• (cyclohexene carbonate)s was carried out by the β-diiminate (BDI) zinc-catalyzed block copolymerization of functionalized epoxides and CO2 with a norbornenyl-containing initiator (Scheme 5) [68]. The subsequent “grafting through” by ROMP of norbornene resulted in the synthesis of multiblock copolymer brushes

First synthesis of cryptands with sucrose scaffold

• Patrycja Sokołowska,
• Michał Kowalski and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2019, 15, 210–217, doi:10.3762/bjoc.15.20

• , 19.84; found: C, 58.12; H, 5.67; I, 19.79. Cryptand 11: To a solution of 10 (258 mg, 0.20 mmol) in acetonitrile (7 mL), powdered potassium carbonate (342 mg, 3.227 mmol, 16 equiv) was added, followed by aza-crown 8 (53 mg, 0.20 mmol, 1 equiv), and the mixture was stirred and boiled under reflux for 24 h

• , 27.32. Synthesis of cryptand 23: To a solution of 22 (118 mg, 0.09 mmol) in acetonitrile (15 mL), powdered potassium carbonate (270 mg, 2.55 mmol, 30 equiv) was added, followed by amine 15 (40 mg, 0.09 mmol, 1.1 equiv), and the mixture was stirred and boiled under reflux for 24 h (TLC monitoring

Systematic synthetic study of four diastereomerically distinct limonene-1,2-diols and their corresponding cyclic carbonates

• Hiroshi Morikawa,
• Jun-ichi Yamaguchi,
• Shun-ichi Sugimura,
• Masato Minamoto,
• Yuuta Gorou,
• Hisatoyo Morinaga and
• Suguru Motokucho

Beilstein J. Org. Chem. 2019, 15, 130–136, doi:10.3762/bjoc.15.13

• )-limonene-derived diol and its corresponding five-membered cyclic carbonate were prepared. The diol (cyclic carbonate) comprises four diastereomers based on the stereochemical configuration of the diol (and cyclic carbonate) moiety. By choosing the appropriate starting compounds (trans- and cis-limonene

• their characteristic signals. Keywords: cyclic carbonate; diastereomer; diol; limonene; NMR; Introduction (R)-Limonene (LM) is a naturally occurring terpene, and therefore a very attractive and renewable resource [1]. Its derivatives have versatilely and widely been studied [1][2][3][4]. Otherwise

• with triphosgene. Neither of the desired products 1b and 1c have been synthesised until now. When 2c was used, the carbonation proceeded smoothly to afford the corresponding carbonate 1c exclusively. The isolated yield after purification was moderate (58%). Conversely, the reaction of 2b was