Room-temperature Pd/Ag direct arylation enabled by a radical pathway

• Amy L. Mayhugh and
• Christine K. Luscombe

Beilstein J. Org. Chem. 2020, 16, 384–390, doi:10.3762/bjoc.16.36

• reported for decarboxylative coupling between indole and 2-nitrobenzoic acids at 110 °C [18]. Under such conditions, silver carboxylates decompose to produce carbonyl and phenyl radicals, which could explain the origin of nitrobenzene incorporation [19][20]. When the radical trapping agent BHT was added to

p-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies

• Panagiotis S. Gritzapis,
• Panayiotis C. Varras,
• Nikolaos-Panagiotis Andreou,
• Katerina R. Katsani,
• Konstantinos Dafnopoulos,
• George Psomas,
• Zisis V. Peitsinis,
• Alexandros E. Koumbis and
• Konstantina C. Fylaktakidou

Beilstein J. Org. Chem. 2020, 16, 337–350, doi:10.3762/bjoc.16.33

• experimental values are shown in Table 1. DNA binding studies Our previous DNA-binding studies with a series of amidoxime, ethanone oxime and aldoxime carboxylates as well as sulfonates of high, moderate or poor DNA photocleaving ability showed no substantial differences on the DNA affinities among the three

• according to previously reported methods [9]. General structures of oxime derivatives with possible DNA photocleavage ability. Left: Oxime carboxylates: O-acyl amidoximes (I), O-acyl ketoximes (II), O-acyl aldoximes (III). Centre: Oxime sulfonates: O-sulfonyl amidoximes (IV), O-sulfonyl ketoximes (V). Right

Ultrasonic-assisted unusual four-component synthesis of 7-azolylamino-4,5,6,7-tetrahydroazolo[1,5-a]pyrimidines

• Yana I. Sakhno,
• Maryna V. Murlykina,
• Oleksandr I. Zbruyev,
• Anton V. Kozyryev,
• Svetlana V. Shishkina,
• Dmytro Sysoiev,
• Vladimir I. Musatov,
• Sergey M. Desenko and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2020, 16, 281–289, doi:10.3762/bjoc.16.27

• -aryl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidine-7-carboxylates (substituents = H, CH3) 4d–o were isolated in 45–80% yields (Scheme 4, Table 1). The same products were isolated while carrying out this reaction in acetic acid at room temperature with intensive stirring instead of ultrasonic irradiation

Bacterial terpene biosynthesis: challenges and opportunities for pathway engineering

• Eric J. N. Helfrich,
• Geng-Min Lin,
• Christopher A. Voigt and
• Jon Clardy

Beilstein J. Org. Chem. 2019, 15, 2889–2906, doi:10.3762/bjoc.15.283

• further oxidation to carbonyls or carboxylates. Other reactions, such as epoxidation, ether bond formation, and structural rearrangement have also been reported (Figure 7). CYP114 in gibberellin (5) biosynthesis, for example, catalyzes the unique oxidation/six-membered to five-membered ring contraction of

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• over Mg2+ ions, and relative insensitivity to pH in biological media due to the relatively low pKa of the electron-poor aniline nitrogens [1]. BAPTA-type molecules complex Ca2+ in an octacoordinated fashion, involving the two aniline functions, the two central ether oxygens and the four carboxylates

Synthesis of aryl-substituted thieno[3,2-b]thiophene derivatives and their use for N,S-heterotetracene construction

• Nadezhda S. Demina,
• Nikita A. Kazin,
• Nikolay A. Rasputin,
• Roman A. Irgashev and
• Gennady L. Rusinov

Beilstein J. Org. Chem. 2019, 15, 2678–2683, doi:10.3762/bjoc.15.261

• . N. Yeltsin, Mira St., 19, Ekaterinburg, 620002, Russia 10.3762/bjoc.15.261 Abstract Fiesselmann thiophene synthesis was applied for the convenient construction of thieno[3,2-b]thiophene derivatives. Thus, new 5- or 6-aryl-3-hydroxythieno[3,2-b]thiophene-2-carboxylates were obtained by condensation

• of 5- or 4-aryl-3-chlorothiophene-2-carboxylates, respectively, with methyl thioglycolate in the presence of potassium tert-butoxide. The saponification of the resulting esters, with decarboxylation of the intermediating acids, gave the corresponding thieno[3,2-b]thiophen-3(2H)-ones. The latter

• synthesis [16], viz., the interaction of ethyl thioglycolate with ethyl 3-chlorobenzo[b]thiophene-2-carboxylates, to form a benzo[b]thieno[2,3-d]thiophene scaffold [17][18], we have decided to apply a similar approach to the synthesis of aryl-substituted TT derivatives. Thus, 3-chloro- or 3-bromothiophene-2

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• , substitution of fluorine and/or the addition of nucleophiles to the electron-poor double bond take place. Therefore, tert-butyl protection is required for carboxylates present in diarylethenes with “oxidized” benzothiophene units and perfluorocyclopentene rings. Photoswitches containing the free carboxylic

Cyclopropanation–ring expansion of 3-chloroindoles with α-halodiazoacetates: novel synthesis of 4-quinolone-3-carboxylic acid and norfloxacin

• Sara Peeters,
• Linn Neerbye Berntsen,
• Pål Rongved and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2019, 15, 2156–2160, doi:10.3762/bjoc.15.212

• retrosynthetic approach towards quinolone-3-carboxylates, as outlined in Scheme 2. Cyclopropanation–ring expansion of 3-chloroindole derivatives with X-EDA would give ethyl 4-chloro-quinoline-3-carboxylates, which would subsequently undergo alcoholysis to give 4-quinolone-3-carboxylates. Results and Discussion

• Detailed experimental procedures and analytical data for the compounds are available in Supporting Information File 1. General procedure for the synthesis of ethyl 4-chloroquinoline-3-carboxylates from X-EDA and 3-chloroindoles X-EDA was synthesized according to a literature procedure [35]. This gave X-EDA

• -chloroquinoline-3-carboxylates to ethyl 4(1H)-oxoquinolone-3-carboxylates [33] To the desired ethyl 4-chloro-quinoline-3-carboxylate derivative (1–2 mmol) was added 5 mL dry ethanol. This solution was refluxed for 24 h or monitored by TLC analysis. The reaction mixture was cooled after the starting material was

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

• racemization, alternative three-carbon chirons would be of great value in enantioselective syntheses of natural compounds and/or drugs. This review article summarizes applications of N-(1-phenylethyl)aziridine-2-carboxylates, -carbaldehydes and -methanols in syntheses of approved drugs and potential

• catalytic hydrogenation but metal-ammonia reduction (Birch reaction) and organic acid in anisole (vide infra) can be efficiently applied. We begin with a short presentation of syntheses of aziridine-2-carboxylates, the corresponding aldehydes and 2-methanols. Review Syntheses of starting materials Synthesis

• of N-(1-phenylethyl)aziridine-2-carboxylates 5 In general, enantiomerically pure starting materials used in asymmetric syntheses are prepared from natural products. This does not hold for N-(1-phenylethyl)aziridine-2-carboxylates 5 since after synthesis in the Gabriel–Cromwell reaction between 3,3

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

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• carbon–carbon triple bond attached to a nitrogen atom that gives them both nucleophilic and electrophilic properties. This dual reactivity is similar to that shown by isocyanides, as they may react with iminium ions and carboxylates as isocyanides do. However, in comparison with the typical Ugi-4CR where

Novel (2-amino-4-arylimidazolyl)propanoic acids and pyrrolo[1,2-c]imidazoles via the domino reactions of 2-amino-4-arylimidazoles with carbonyl and methylene active compounds

• Victoria V. Lipson,
• Tetiana L. Pavlovska,
• Nataliya V. Svetlichnaya,
• Anna A. Poryvai,
• Nikolay Yu. Gorobets,
• Erik V. Van der Eycken,
• Irina S. Konovalova,
• Svetlana V. Shiskina,
• Alexander V. Borisov,
• Vladimir I. Musatov and
• Alexander V. Mazepa

Beilstein J. Org. Chem. 2019, 15, 1032–1045, doi:10.3762/bjoc.15.101

• -arylpropanoic acids. The interaction of 2-amino-4-arylimidazoles with aromatic aldehydes or isatins and acyclic methylene active compounds has led to the formation of pyrrolo[1,2-c]imidazole-6-carbonitriles, pyrrolo[1,2-с]imidazole-6-carboxylates and spiro[indoline-3,7'-pyrrolo[1,2-c]imidazoles], which can be

• ]imidazole-6-carboxylates. A mixture of the corresponding 2-amino-4-arylimidazole 1 (1.0 mmol), aromatic aldehyde 2 (2.0 mmol) and ethyl 2-cyanoacetate 15 (1.0 mmol) in 2 mL of 2-propanol was refluxed during 20–30 min. After cooling, the yellow solid products 16 were filtered off and crystallized from iPrOH

• : С, 69.43; H, 5.07; N, 22.64. General procedure for the synthesis of 3',5'-diamino-1-alkyl-2-oxo-1'-arylspiro[indoline-3,7'-pyrrolo[1,2-c]imidazole]-6'-carboxylates: The mixture of corresponding 2-amino-4-arylimidazoles 1 (1.0 mmol), isatin 18 (1.0 mmol) and ethyl 2-cyanoacetate 15 (1.0 mmol) in 2 mL

Coordination chemistry and photoswitching of dinuclear macrocyclic cadmium-, nickel-, and zinc complexes containing azobenzene carboxylato co-ligands

• Jennifer Klose,
• Tobias Severin,
• Peter Hahn,
• Alexander Jeremies,
• Jens Bergmann,
• Daniel Fuhrmann,
• Jan Griebel,
• Bernd Abel and
• Berthold Kersting

Beilstein J. Org. Chem. 2019, 15, 840–851, doi:10.3762/bjoc.15.81

• 5–8 display an isostructural series of compounds with bridging azobenzene carboxylates in the trans form. The paramagnetic Ni complexes 2, 4 and 7 reveal a weak ferromagnetic exchange interaction with magnetic exchange coupling constant values between 21 and 23 cm−1 (H = −2JS1S2). Irradiation of 1

• with λ = 365 nm reveals a photoisomerization of the co-ligand from the trans to the cis form. Keywords: azobenzene carboxylates; cadmium; complexes; macrocyclic ligands; nickel; zinc; Introduction The macrocyclic N6S2 donor ligand H2L is an effective dinucleating ligand that supports a large number

• redox potential [6]. The facile formation of such compounds and their unusual properties led us to synthesize derivatives bearing azobenzene carboxylates as bridging co-ligands. A series of mixed-ligand complexes of the type [M2L(μ-L')]+, where M = Zn(II), Ni(II), or Cd(II), L' = p-azobenzene

Synthesis and selected transformations of 2-unsubstituted 1-(adamantyloxy)imidazole 3-oxides: straightforward access to non-symmetric 1,3-dialkoxyimidazolium salts

• Grzegorz Mlostoń,
• Małgorzata Celeda,
• Katarzyna Urbaniak,
• Marcin Jasiński,
• Vladyslav Bakhonsky,
• Peter R. Schreiner and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2019, 15, 497–505, doi:10.3762/bjoc.15.43

• types of adamantylation reactions (C-, N-, or O-adamantylation) attract attention, and typically 1,3-dehydroadamantane [28] or 1-haloadamantanes [29] are applied as alkylating reagents. Adamantan-1-yl carboxylates are also known as efficient adamantylating reagents [30]. In spite of the fact that

Synthesis of 1,2-divinylcyclopropanes by metal-catalyzed cyclopropanation of 1,3-dienes with cyclopropenes as vinyl carbene precursors

• Jesús González,
• Alba de la Fuente,
• María J. González,
• Laura Díez de Tejada,
• Luis A. López and
• Rubén Vicente

Beilstein J. Org. Chem. 2019, 15, 285–290, doi:10.3762/bjoc.15.25

• equimolar mixture of cis/trans diastereoisomers (cis refers to both vinyl substituents). Even though the lack of selectivity was already noticed by Uemura and co-workers in related reactions [17], we attempted the reaction with other zinc salts or rhodium(II) carboxylates as catalysts. Unfortunately, these

Dynamic light scattering studies of the effects of salts on the diffusivity of cationic and anionic cavitands

• Anthony Wishard and
• Bruce C. Gibb

Beilstein J. Org. Chem. 2018, 14, 2212–2219, doi:10.3762/bjoc.14.195

• effects, but these are usually much weaker, and we believe there are two reasons for this. First, simple metal cations are generally more strongly solvated than comparable anions that can induce Hofmeister effects. Second, the anions that predominate in biomacromolecules are carboxylates, phosphates and

• ] (Figure 1), to different salts using dynamic light scattering (DLS) [17][18][19][20]. Respectively functionalized with carboxylates and trimethylammonium groups, these hosts are expected to possess unique ion-pairing properties and hence have very different reverse-Hofmeister responses to added salts

• be as strong as 4.60 kcal mol−1. Host 2 has a second anion binding site in the form of the crown of trimethylammoniums “under” the primary bowl [14], and correspondingly the four chelating carboxylates of the crown of 1 may be a reasonable cation binding site. Furthermore, in addition to these

Thiocarbonyl-enabled ferrocene C–H nitrogenation by cobalt(III) catalysis: thermal and mechanochemical

• Santhivardhana Reddy Yetra,
• Zhigao Shen,
• Hui Wang and
• Lutz Ackermann

Beilstein J. Org. Chem. 2018, 14, 1546–1553, doi:10.3762/bjoc.14.131

• by weakly-coordinating thiocarbonyl-assisted cobalt catalysis. Thus, carboxylates enabled ferrocene C–H nitrogenations with dioxazolones, featuring ample substrate scope and robust functional group tolerance. Mechanistic studies provided strong support for a facile organometallic C–H activation

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

• Veronika Hladíková,
• Jiří Váňa and
• Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

• corresponding rather to type II or even type I cycloadditions. The most reactive were electron-poor alkynes (acetylene(di)carboxylates, benzoyl phenylacetylene) while electron-rich alkynes (tetradec-1-yne, 1-phenylpropyne) were much less reactive. Unfortunately, the reaction rate constant was not measured for

• vessels is inconvenient and may be even dangerous. Two strategies can overcome such problems: liquid DMAD, diethyl acetylenedicarboxylate or alkyl propiolate can be used instead of acetylene and the resulting pyrazole-3,4-dicarboxylates or pyrazole-3-/4-carboxylates can then undergo hydrolysis and

• ). A completely different ratio of both isomers was observed when Cu(II) carboxylates and acetylacetonates were employed instead of Cu(OTf)2. This was explained by different operating mechanisms. While Cu(OTf)2, Cu(TFA)2 and Cu(BF4)2 behave mainly as Lewis acids, other Cu(II) salts/complexes

An unusual thionyl chloride-promoted C−C bond formation to obtain 4,4'-bipyrazolones

• Gernot A. Eller,
• Gytė Vilkauskaitė,
• Algirdas Šačkus,
• Vytas Martynaitis,
• Ashenafi Damtew Mamuye,
• Vittorio Pace and
• Wolfgang Holzer

Beilstein J. Org. Chem. 2018, 14, 1287–1292, doi:10.3762/bjoc.14.110

• of 5-hydroxypyrazole-4-carboxylates in refluxing thionyl chloride. The obtained diesters can be transformed into the corresponding 4,4'-bipyrazoles via alkaline hydrolysis and subsequent decarboxylation. Detailed NMR spectroscopic investigations (1H, 13C, 15N) were undertaken with all products

• in a convenient access to 1-substituted or 1,3-disubstituted 5-chloropyrazole-4-carboxylates required as valuable precursors for further functionalizations. Such compounds have been mainly prepared from the corresponding 5-aminopyrazole-4-carboxylates via (non-aqueous) diazotation and subsequent

• subsequently converted into the ethyl esters by treatment with EtOH/H2SO4 [15]. However, as the latter approach is tedious and the former one uses toxic substances we envisaged to convert the easily available 5-hydroxypyrazole-4-carboxylates 1 into the corresponding 5-chloro derivatives 2 by the action of an

Selective carboxylation of reactive benzylic C–H bonds by a hypervalent iodine(III)/inorganic bromide oxidation system

• Toshifumi Dohi,
• Shohei Ueda,
• Kosuke Iwasaki,
• Yusuke Tsunoda,
• Koji Morimoto and
• Yasuyuki Kita

Beilstein J. Org. Chem. 2018, 14, 1087–1094, doi:10.3762/bjoc.14.94

• electrophilic aromatic rings, non-acidic carbonyl groups, and suitable oxygen, nitrogen, and sulfur functionalities. Carbonyloxy radicals derived from typical hypervalent iodine(III) carboxylates by photolysis and other conditions [65][66][67][68] are known to undergo irreversible decarboxylation [69][70

Polysubstituted ferrocenes as tunable redox mediators

• Sven D. Waniek,
• Jan Klett,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2018, 14, 1004–1015, doi:10.3762/bjoc.14.86

• reactions [29], borylations of arenediazonium salts [30] and in C–H imidation reactions of (hetero)arenes [31] (Scheme 1b,c). Ferrocene has been used as redox mediator for the electrochemical modification of carbon surfaces via electrochemical oxidation of carboxylates [32][33], as mediator for

One-pot preparation of 4-aryl-3-bromocoumarins from 4-aryl-2-propynoic acids with diaryliodonium salts, TBAB, and Na₂S₂O₈

• Teppei Sasaki,
• Katsuhiko Moriyama and
• Hideo Togo

Beilstein J. Org. Chem. 2018, 14, 345–353, doi:10.3762/bjoc.14.22

• N-arylation of NH groups under metal-free conditions [35][36][37][38][39]. For example, treatment of arenecarboxylic acids and alkanecarboxylic acids with diaryliodonium salts and t-BuOK under toluene refluxing conditions provides the corresponding aryl carboxylates in good yields [40][41]. However

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• -trifluoromethylpyrazolo[1,5-a]pyrimidine derivative 124 by dehydration on refluxing with acetic anhydride (Scheme 34). All the synthesized compounds were screened for their anti-inflammatory activity. Mulakayala and co-workers [91] synthesized 7-trifluoromethylpyrazolo[1,5-a]pyrimidine carboxylates 127 by the reaction of

• al. [94] reported the synthesis of aminobenzothiazole linked pyrazolo[1,5-a]pyrimidine conjugates (benzothiazolyl derivatives, 136). Methyl-2,7-diphenylpyrazolo[1,5-a]pyrimidine-5-carboxylates, obtained by the reactions of 5-aminopyrazole 16 with aryl-β-diketoesters 133 in ethanol, were hydrolyzed in

• )prop-2-en-1-one 162 in aqueous ethanol at ambient temperature through the intermediacy of methyl 7-heteroarylpyrazolo[1,5-a]pyrimidine-3-carboxylates 163 which was subsequently hydrolyzed to give the corresponding carboxylic acids 164 followed by coupling with various primary and secondary amines 165

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

• three-step process. The protocol utilized the photodecarboxylative addition of readily available carboxylates to N-(bromoalkyl)phthalimides as a versatile and efficient key step. The initially obtained hydroxyphthalimidines were readily converted to the desired N-diaminoalkylated 3-arylmethylene-2,3

Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides

• Irwan Iskandar Roslan,
• Kian-Hong Ng,
• Gaik-Khuan Chuah and
• Stephan Jaenicke

Beilstein J. Org. Chem. 2017, 13, 2739–2750, doi:10.3762/bjoc.13.270

• ). Good to excellent yields were also obtained with electron-withdrawing ester and CF3 moieties (Scheme 3, 5h–j). Likewise, the reaction with 2-aminobenzoxazole proceeded smoothly giving 5k in 79% yield. Next, a variety of methyl or ethyl carboxylates of β-ketoesters were screened for this reaction. Good