Synthesis of a leopolic acid-inspired tetramic acid with antimicrobial activity against multidrug-resistant bacteria

• Luce Mattio,
• Loana Musso,
• Leonardo Scaglioni,
• Andrea Pinto,
• Piera Anna Martino and
• Sabrina Dallavalle

Beilstein J. Org. Chem. 2018, 14, 2482–2487, doi:10.3762/bjoc.14.224

• intermediate 10 by treatment of compound 9 with potassium tert-butoxide (1 M in THF) in THF [24]. The optimisation of reaction conditions, work-up and purification, allowed us to obtain the desired compound in 65% yield. Before removing the PMB group and installing the ureidodipeptide fragment, we needed to

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• potassium tert-butoxide. Several substituted 5- to 8-membered ring π-conjugated systems are isolated in moderate to high yields. Mechanistic investigations for the iodine/sulfur exchange have led to propose the initial formation of the trisulfur radical anion S3•– 72, which adds to the diaryliodonium moiety

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

Transition-metal-free [3 + 3] annulation of indol-2-ylmethyl carbanions to nitroarenes. A novel synthesis of indolo[3,2-b]quinolines (quindolines)

• Michał Nowacki and
• Krzysztof Wojciechowski

Beilstein J. Org. Chem. 2018, 14, 194–202, doi:10.3762/bjoc.14.14

• base such as potassium tert-butoxide to form the σH-adduct in high concentration. This σH-adduct is then treated with a silylating agent and a weaker base to form the final product. Results and Discussion In this paper, we present the transformation of σH-adducts, formed from indol-2-ylmethyl

• , we decided to perform a one-pot reaction in which in situ N-silylation furnished the expected carbanion precursor. Thus, when we treated tert-butyl indol-2-ylacetate (1c) and p-chloronitrobenzene (2a) with triethylamine and potassium tert-butoxide and then added trimethylchlorosilane we obtained

The photodecarboxylative addition of carboxylates to phthalimides as a key-step in the synthesis of biologically active 3-arylmethylene-2,3-dihydro-1H-isoindolin-1-ones

• Ommid Anamimoghadam,
• Saira Mumtaz,
• Anke Nietsch,
• Gaetano Saya,
• Cherie A. Motti,
• Jun Wang,
• Peter C. Junk,
• Ashfaq Mahmood Qureshi and
• Michael Oelgemöller

Beilstein J. Org. Chem. 2017, 13, 2833–2841, doi:10.3762/bjoc.13.275

• ca. 8.7 at the end of the irradiation. Temperature control was crucial as thermal conversion of 3a into 4 was found to occur above 40 °C. Compound 1a could be converted quantitatively to the oxazolidine derivative 4 by treatment with either sodium carbonate or potassium tert-butoxide in acetonitrile

• compound 1a was treated with either sodium carbonate or potassium tert-butoxide it was indeed converted quantitatively to the oxazolidine derivative 4. Similarly, the final benzylated hydroxyphthalimidine may undergo cyclization instead (path C), as was found to occur at elevated temperature of >40 °C

Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269

• -isomers more favorable [40]. Vinylphosphonium salts can also be directly converted into the corresponding ylides by potassium tert-butoxide and subjected to the Wittig reaction as described by Yamamoto et al. (Scheme 25). The transformation resulted in polyenes 35 of Z-configuration in a relatively low

• and Grignard reagents. Direct transformation of vinylphosphonium salts into ylides in the presence of potassium tert-butoxide and their subsequent Wittig reaction with aldehydes. A general method for synthesis of carbo- and heterocyclic systems by the intramolecular Wittig reaction from

Synthesis of benzannelated sultams by intramolecular Pd-catalyzed arylation of tertiary sulfonamides

• Valentin A. Rassadin,
• Mirko Scholz,
• Anastasiia A. Klochkova,
• Armin de Meijere and
• Victor V. Sokolov

Beilstein J. Org. Chem. 2017, 13, 1932–1939, doi:10.3762/bjoc.13.187

• equivalents of NaH. Although full conversion of 8a was achieved and the NMR-determined yield of sultam 10a was 89% (Table 1, entry 1), attempts were made to further improve the reaction conditions by testing different bases such as potassium tert-butoxide and sodium methoxide in dioxane and potassium

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

Efficient mechanochemical synthesis of regioselective persubstituted cyclodextrins

• Laszlo Jicsinszky,
• Marina Caporaso,
• Katia Martina,
• Emanuela Calcio Gaudino and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2016, 12, 2364–2371, doi:10.3762/bjoc.12.230

• (entries 22, 23, and 26–28 in Table 1) despite the use of the considerably milder and safer base, potassium tert-butoxide (KOt-Bu). Our first target was to investigate the reaction between a good nucleophile (sulfur) and per-halogenated CDs. The TU method is widely used in the synthesis of various thiols

Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes

• Michael Nonnenmacher,
• Dominik M. Buck and
• Doris Kunz

Beilstein J. Org. Chem. 2016, 12, 1884–1896, doi:10.3762/bjoc.12.178

• mL of tetrahydrofuran was cooled to −35 °C and a solution of potassium tert-butoxide (14.9 mg, 133 μmol) in 1 mL tetraydrofuran was added. After 30 min the deep red suspension was warmed up to room temperature and stirred overnight. The solvent was removed in vacuo and the residue suspended in 7 mL

Three-component synthesis of highly functionalized aziridines containing a peptide side chain and their one-step transformation into β-functionalized α-ketoamides

• Lena Huck,
• Juan F. González,
• Elena de la Cuesta and
• J. Carlos Menéndez

Beilstein J. Org. Chem. 2016, 12, 1772–1777, doi:10.3762/bjoc.12.166

• of 1,4-diacetyl-2,5-piperazinedione with aldehydes in the presence of potassium tert-butoxide, followed by deacetylation with hydrazine hydrate (see the Supporting Information File 1 for further details). As shown in Scheme 2, treatment of these materials with N-bromosuccinimide and methanol in

Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• led to low conversion. The use of potassium tert-butoxide was found to be essential to achieve good reactivity and enantioselectivity. Other amino-protecting groups (Boc, phthalimido) or tertiary N-methylated variants rendered the 1,4-acceptor unreactive. Glorius and co-workers proposed that an

Unusual traits of cis and trans-2,3-dibromo-1,1-dimethylindane on the way from 1,1-dimethylindene to 2-bromo-, 3-bromo-, and 2,3-dibromo-1,1-dimethylindene

• Rudolf Knorr,
• David S. Stephenson,
• Ernst Lattke,
• Petra Böhrer and
• Jakob Ruhdorfer

Beilstein J. Org. Chem. 2016, 12, 1178–1184, doi:10.3762/bjoc.12.113

• Scheme 2) [10]. We observed a less distinct kinetic preference in the corresponding base-induced processes: In di(2-methoxyethyl) ether (diglyme) as the solvent, a substoichiometric amount of KOt-Bu (potassium tert-butoxide) reacted faster with cis-1 than with trans-1 by a factor of roughly 9 at room

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• nine-membered carbocyclic ring. Treatment of this intermediate with potassium tert-butoxide led to the cleavage of the 2-cyanoethylsulfide moiety and the generation of a thiolate anion, which underwent SN2 displacement of the primary mesylate, affording the 13-membered lactam 56. The stage was now set

Comparison of the catalytic activity for the Suzuki–Miyaura reaction of (η⁵-Cp)Pd(IPr)Cl with (η³-cinnamyl)Pd(IPr)(Cl) and (η³-1-t-Bu-indenyl)Pd(IPr)(Cl)

• Patrick R. Melvin,
• Nilay Hazari,
• Hannah M. C. Lant,
• Ian L. Peczak and
• Hemali P. Shah

Beilstein J. Org. Chem. 2015, 11, 2476–2486, doi:10.3762/bjoc.11.269

• one hour and stored under dinitrogen. Potassium tert-butoxide (99.99%, sublimed) was purchased from Aldrich. Potassium carbonate was purchased from Mallinckrodt and ground up with a mortar and pestle and stored in an oven at 130 °C prior to use. 1,3-Divinyltetramethyldisiloxane was purchased from TCI

Deproto-metallation of N-arylated pyrroles and indoles using a mixed lithium–zinc base and regioselectivity-computed CH acidity relationship

• Mohamed Yacine Ameur Messaoud,
• Ghenia Bentabed-Ababsa,
• Madani Hedidi,
• Aïcha Derdour,
• Floris Chevallier,
• Yury S. Halauko,
• Oleg A. Ivashkevich,
• Vadim E. Matulis,
• Laurent Picot,
• Valérie Thiéry,
• Thierry Roisnel,
• Vincent Dorcet and
• Florence Mongin

Beilstein J. Org. Chem. 2015, 11, 1475–1485, doi:10.3762/bjoc.11.160

• hexane (thermodynamic conditions) [11][12] or (ii) with butyllithium activated by potassium tert-butoxide (LICKOR) in tetrahydrofuran (THF) at −75 °C [11][13]. N-Arylpyrroles substituted on their six-membered ring by methoxy [14], halogen [15][16], alkyl [17][18], or trifluoromethyl [19][20] groups have

Antioxidant potential of curcumin-related compounds studied by chemiluminescence kinetics, chain-breaking efficiencies, scavenging activity (ORAC) and DFT calculations

• Adriana K. Slavova-Kazakova,
• Silvia E. Angelova,
• Timur L. Veprintsev,
• Petko Denev,
• Davide Fabbri,
• Maria Antonietta Dettori,
• Maria Kratchanova,
• Vladimir V. Naumov,
• Aleksei V. Trofimov,
• Rostislav F. Vasil’ev,
• Giovanna Delogu and
• Vessela D. Kancheva

Beilstein J. Org. Chem. 2015, 11, 1398–1411, doi:10.3762/bjoc.11.151

• solution of potassium tert-butoxide (1.75 g, 15.6 mmol) in tetrahydrofuran (20 mL) was added dropwise a solution of dehydrozingerone (2, 1 g, 5.2 mmol) in THF (15 mL) at room temperature under N2 atmosphere. The reaction mixture was stirred at room temperature for 10 min. Diethyl oxalate (1.1 mL, 7.8 mmol

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• ) delivered ketophenol 335 (37%), which on further treatment with potassium tert-butoxide/methyltriflate mixture, gave the dimethyl ether bis[10]paracyclophane 336 (63%, Scheme 58). In 1980, Gassman and co-workers [194] have synthesized [8]paracyclophane via the DA reaction as a key step. In this connection

NAA-modified DNA oligonucleotides with zwitterionic backbones: stereoselective synthesis of A–T phosphoramidite building blocks

• Boris Schmidtgall,
• Claudia Höbartner and
• Christian Ducho

Beilstein J. Org. Chem. 2015, 11, 50–60, doi:10.3762/bjoc.11.8

• stability, thymidine-5'-aldehydes 10 and 11 were not stored, but directly used for the subsequent Wittig–Horner reaction. They were therefore converted with glycine-derived phosphonate 12 [51][52][53][54] in the presence of potassium tert-butoxide as a base. As anticipated [47][48][55], these reactions

Efficient deprotection of F-BODIPY derivatives: removal of BF₂ using Brønsted acids

• Mingfeng Yu,
• Joseph K.-H. Wong,
• Cyril Tang,
• Peter Turner,
• Matthew H. Todd and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 37–41, doi:10.3762/bjoc.11.6

• : potassium tert-butoxide in tert-butanol/water with microwave heating to 90–140 °C (26–98% yield) [15][16]. Kusaka et al. built on this strategy to achieve deboration of F-BODIPYs using sodium tert-butoxide in refluxing toluene (59–83% yield) en route to bis(dipyrrinato)zinc(II) complexes [17]. Two very

(2R,1'S,2'R)- and (2S,1'S,2'R)-3-[2-Mono(di,tri)fluoromethylcyclopropyl]alanines and their incorporation into hormaomycin analogues

• Armin de Meijere,
• Sergei I. Kozhushkov,
• Dmitrii S. Yufit,
• Christian Grosse,
• Marcel Kaiser and
• Vitaly A. Raev

Beilstein J. Org. Chem. 2014, 10, 2844–2857, doi:10.3762/bjoc.10.302

• , the conversion of 20 was quantitative, and the yield of 21 was excellent (98%). In the final step, the attempted 1,3-dehydrotosylation of 22 with potassium tert-butoxide, when carried out in dimethyl sulfoxide as reported [26][27], compound 23 as an intermolecular condensation product of the expected

Synthesis of new, highly luminescent bis(2,2’-bithiophen-5-yl) substituted 1,3,4-oxadiazole, 1,3,4-thiadiazole and 1,2,4-triazole

• Anastasia S. Kostyuchenko,
• Vyacheslav L.Yurpalov,
• Aleksandra Kurowska,
• Wojciech Domagala,
• Adam Pron and
• Alexander S. Fisyuk

Beilstein J. Org. Chem. 2014, 10, 1596–1602, doi:10.3762/bjoc.10.165

• reacting with ethyl mercaptoacetate in a basic medium. The yields of 5 and 6 were 76% and 49%, respectively. Ethyl 4-(hexyloxy)-2,2'-bithiophene-5-carboxylate (7) was obtained by the alkylation of 6 with hexyl iodide in the presence of potassium tert-butoxide in 81% yield (Scheme 2). Compounds 5–7 were

Streptopyridines, volatile pyridine alkaloids produced by Streptomyces sp. FORM5

• Ulrike Groenhagen,
• Michael Maczka,
• Jeroen S. Dickschat and
• Stefan Schulz

Beilstein J. Org. Chem. 2014, 10, 1421–1432, doi:10.3762/bjoc.10.146

• added. Afterwards the mixture was allowed to warm to −30 °C in 2 h and again phenyllithium solution (1.63 mL, 15.5 mmol) was added. Then the mixture was cooled down again to −78 °C and potassium tert-butoxide (2.61 g, 23.25 mmol) was added. Overnight the mixture was allowed to warm to rt and quenched

An economical and safe procedure to synthesize 2-hydroxy-4-pentynoic acid: A precursor towards ‘clickable’ biodegradable polylactide

• Quanxuan Zhang,
• Hong Ren and
• Gregory L. Baker

Beilstein J. Org. Chem. 2014, 10, 1365–1371, doi:10.3762/bjoc.10.139

• [30] to provide propargyl tosylate in high yield as a dark liquid after drying under vacuum. Diethyl 2-acetamidomalonate (4), deprotonated by potassium tert-butoxide, was alkylated in dioxane by a conventional C-alkylation method [31][32][33][34] with propargyl tosylate to give propargylic derivative

• (s, 3H); 13C NMR (125 MHz, CDCl3) δ 145.3, 133.1, 130.0, 128.2, 77.4, 75.4, 57.44, 21.8. Synthesis of diethyl α-propargyl-α-acetamidomalonate (5) To a solution of 105 g (0.483 mol) of diethyl 2-acetamidomalonate (4) in 1.35 L of dioxane was added a slurry of 61 g (0.54 mol) of potassium tert-butoxide

Addition of H-phosphonates to quinine-derived carbonyl compounds. An unexpected C9 phosphonate–phosphate rearrangement and tandem intramolecular piperidine elimination

• Łukasz Górecki,
• Artur Mucha and
• Paweł Kafarski

Beilstein J. Org. Chem. 2014, 10, 883–889, doi:10.3762/bjoc.10.85

• chromatography, for details see Supporting Information File 1). C9 position modification, phosphonate–phosphate rearrangement Oxidation of the C9 hydroxy group of quinine to the corresponding ketone, quininone, was performed with potassium tert-butoxide and benzophenone (Scheme 4) [34]. Using toluene as the