Regioselectively α- and β-alkynylated BODIPY dyes via gold(I)-catalyzed direct C–H functionalization and their photophysical properties

• Takahide Shimada,
• Shigeki Mori,
• Masatoshi Ishida and
• Hiroyuki Furuta

Beilstein J. Org. Chem. 2020, 16, 587–595, doi:10.3762/bjoc.16.53

• ., bromination) of BODIPY derivatives often affords a mixture of multiply halogenated products, which is tedious to separate by column chromatography. The introduction of one or more alkynyl groups into the BODIPY skeleton indeed produces useful building blocks for functional π-materials. For example, ethynyl

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• heteroaromatic derivatives. Noteworthy, when the reaction was carried out in acetonitrile, azido bromination and diazidation reactions were possible using 10 equivalents of NaBr and NaN3, respectively. Notably, when the reaction was carried out in the dark, the diazidation reaction of the olefins occurred, while

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• photolysis. The mechanism involved in this transformation is shown in Figure 20. Aryl C–H halogenation Aerobic bromination of arenes: In another experiment, Ohkubo et al. reported that for aerobic aryl C–H brominations, HBr can be utilized with photoredox catalyst 2 in the presence of molecular oxygen to

• compounds via an oxidative photocatalytic pathway [164]. They performed the reaction in the presence of organic photoredox catalyst 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (5a, 4CzIPN), environment friendly oxygen, and hydrochloride as a chloride source. The activation proceeded via bromination

• of substituted phenols using QuCN. Synthesis of substituted phenols with DDQ (5). Aerobic bromination of arenes using an acridinium-based photocatalyst. Aerobic bromination of arenes with anthraquinone. Chlorination of benzene derivatives with Mes-Acr-MeClO4 (2). Chlorination of arenes with 4CzIPN

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

• literature procedure, 2,3-dibromobenzofuran (1) was synthesized by bromination of benzofuran [33]. The Suzuki–Miyaura reaction of 1 with 2-bromophenylboronic acid (2), carried out under standard conditions using Pd(PPh3)4, afforded the desired product 3 in 84% yield and with very good regioselectivity. The

Chemical tuning of photoswitchable azobenzenes: a photopharmacological case study using nicotinic transmission

• Lorenzo Sansalone,
• Jun Zhao,
• Matthew T. Richers and
• Graham C. R. Ellis-Davies

Beilstein J. Org. Chem. 2019, 15, 2812–2821, doi:10.3762/bjoc.15.274

• catalytic hydrogenation to 4 followed by protection with TBDMS to give 5 in 63% yield for three steps. The synthesis of the other half of the photochrome started with bromination of difluorinated aniline to give 6 followed by copper-catalyzed cyanation to 7 in 62% overall yield. Diazonization of 7 with

• % overall yield. Installation of the cationic head was performed in two steps: first bromination of 11 via Appel reaction, followed by treatment with trimethylamine to give 2 in 35% overall yield. Photoswitch 2 is the first example of a bifunctional, asymmetrically substituted 4FAB chromophore that actually

An improved, scalable synthesis of Notum inhibitor LP-922056 using 1-chloro-1,2-benziodoxol-3-one as a superior electrophilic chlorinating agent

• Nicky J. Willis,
• Elliott D. Bayle,
• George Papageorgiou,
• David Steadman,
• Benjamin N. Atkinson,
• William Mahy and
• Paul V. Fish

Beilstein J. Org. Chem. 2019, 15, 2790–2797, doi:10.3762/bjoc.15.271

• functionalised for the introduction of the C7-cyclopropyl group, the C6-chlorine atom and elaboration of the thioacetic acid moiety at C4. Electrophilic bromination at C7 with N-bromosuccinimide gave 5 as the major regioisomer reproducibly on 100 mmol scale in modest yield (41–48%). This proved to be the least

• –26%) and high purity (>99%). Improved synthesis of 1; second generation A shorter synthesis was then developed by accessing bromide 5 by an alternative route. The low-yielding C7 bromination of 4 with NBS to give 5 as described above (Scheme 1, step c) was avoided by starting with 7-bromo-4

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

• ligands. The reaction with pinacolborane (HB(pin)) gave ester 9 in 97% yield [11]. Another ester (10) was synthesized by bromination of 3-thiopheneacetic acid with NBS (applying an ultrasound bath) followed by esterification of the crude product with methanol in the presence of sulfuric acid [12]. Other

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

• and reacted with 3,3-dimethylallyl bromide, followed by changing the protecting group from MOM ether to methyl ether to provide olefin 86. Allylic oxidation of 86 followed by nucleophilic bromination of the resulting allylic alcohol gave bromide 87. Dianion displacement of the bromide of 87 gave ester

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

Remarkable effect of alkynyl substituents on the fluorescence properties of a BN-phenanthrene

• Alberto Abengózar,
• David Sucunza,
• Patricia García-García and
• Juan J. Vaquero

Beilstein J. Org. Chem. 2019, 15, 1257–1261, doi:10.3762/bjoc.15.122

• -aromatics. Interestingly, 1a turned out to be weakly fluorescent [23], in contrast to other BN-phenanthrene isomers described previously [25][26]. The presence of aryl or amino substituents at C1, which can be introduced via bromination and subsequent palladium-catalyzed cross coupling, does not have a

• -phenanthrene 1a and the derivatives prepared in this work are shown in Figure 2. 1-(Phenylethynyl)-4a-aza-10a-boraphenanthrene (5), which was previously prepared in our group by bromination of 1a and subsequent coupling [23], was also included in this comparative study. The absorption and emission data for

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

• drastically alter its structural properties and reactivities. Prominent examples are the cis-bromination of α,β-unsaturated carboxylato ligands [2], regioselective Diels–Alder reactions of encapsulated dienoate ligands [3], and the stabilization of unusual co-ligand conformations, respectively [4]. The

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

• located on the surface of the polymer are capable of various addition reactions (bromination, epoxidation, oxidation) forming films of several tens or hundreds of nanometers thick on the surface. However, no further penetration of reactants into the deeper polydicyclopentadiene layers occurs [28]. It is

Efficient synthesis of 4-substituted-ortho-phthalaldehyde analogues: toward the emergence of new building blocks

• Clémence Moitessier,
• Ahmad Rifai,
• Pierre-Edouard Danjou,
• Isabelle Mallard and
• Francine Cazier-Dennin

Beilstein J. Org. Chem. 2019, 15, 721–726, doi:10.3762/bjoc.15.67

• , rarely recorded in the literature with an efficient synthetic pathway; conjointly to the 3-substituted OPA that is even less described. In 1966, Khan et al. presented the synthesis of 4-hydroxy and 4-methoxy-ortho-phthalaldehyde (4-HO-OPA and 4-MeO-OPA) by bromination and oxidation of 4-hydroxy and 4

Synthesis of 2H-furo[2,3-c]pyrazole ring systems through silver(I) ion-mediated ring-closure reaction

• Vaida Milišiūnaitė,
• Rūta Paulavičiūtė,
• Eglė Arbačiauskienė,
• Vytas Martynaitis,
• Wolfgang Holzer and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2019, 15, 679–684, doi:10.3762/bjoc.15.62

• -trisubstituted 2H-furo[2,3-c]pyrazole-5-carboxylic acids and related carboxamides [11][12]. The aforementioned carboxylic acids have been prepared by bromination of the corresponding pyrano[2,3-c]pyrazol-6(1H)-one derivatives followed by heating of the obtained 5-bromo derivatives in the presence of sodium

Low-budget 3D-printed equipment for continuous flow reactions

• Jochen M. Neumaier,
• Amiera Madani,
• Thomas Klein and
• Thomas Ziegler

Beilstein J. Org. Chem. 2019, 15, 558–566, doi:10.3762/bjoc.15.50

• reagent (Ag2CO3 on Celite) [36][37]. The bromination and glycosylation reaction steps had to be performed in separate reactions. Therefore, we also investigated glycosylations with the respective imidate glycosyl donor 5. First, the cleavage of the anomeric acetyl group with hydrazine acetate was

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

• + chemistry. Finally, Lee et al. [27] studied in detail the regiochemical outcomes of the synthesis of the bromosugars 7a and 7b of the glycosylation of Nam (1a) with these bromosugars as well as the deprotection of the acylated nucleosides 8a,b. It was observed that the bromination of 2a with HBr gas in

• β/α mixture was obtained when 2a was reacted with neat bromotrimethylsilane at room temperature. Bromination of 2b yielded a 10:1 β/α mixture of the anomeric bromide 7b [27]. The reaction between Nam (1a) and the bromide 7a was carried out in liquid SO2 and proceeded in high yields with the

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

• carried out with inexpensive reagents and can also be applied to the distal bromination of cycloalkanols. The possible mechanism is outlined in Scheme 28. The cycloalkoxy radical 98 is generated from cyclopropanol 91 under the action of the metastable Ag(II) species, which is formed by the interaction of

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• -hydroxy-L-glutamic acid derivative 66 (Scheme 16) was required and it was obtained as a single diastereoisomer from 65 in the same way [75][76]. By bromination of L-glutamic acid Bromination of N-phthaloyl-L-glutamic acid [(S)-67] followed by methanolysis gave a 2:1 mixture of threo and erythro

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

• procedure published by Liu et al. [56] and bromination to the new benzyl bromide 9 succeeded with tribromoisocyanuric acid (TBCA) as published by de Almeida et al. [57]. The final transformation of benzyl bromide 9 to triphenylphosphonium charge-tagged 4∙Br was performed with a slightly modified protocol

Enhanced single-isomer separation and pseudoenantiomer resolution of new primary rim heterobifunctionalized α-cyclodextrin derivatives

• Iveta Tichá,
• Gábor Benkovics,
• Milo Malanga and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2018, 14, 2829–2837, doi:10.3762/bjoc.14.261

• regioisomers on the primary rim of homobifunctionalized diazido-α-CDs by selective substitution on the primary rim. Specifically, three positional regioisomers 6A,6B-, 6A,6C-, and 6A,6D-diazido-α-CDs were prepared via different intermediates (using sulfonylation with capping agents, bromination and tosylation

• prepared all possible regioisomers of primary rim-disubstituted α-CD derivatives using the most common CD intermediates by commonly used derivatization (bromination, tosylation and capping). The three positional isomers (AB, AC, AD) were separated by ad hoc-developed HPLC methods, and the regioisomeric

• ). On one hand, a direct bromination of α-CD was performed under Vilsmeier/Haack conditions (reaction 3, Scheme 2) with N-bromosuccinimide (NBS) and Ph3P in N,N-dimethylformamide (DMF). Previous studies have shown that this reaction is highly regioselective for the primary rim of CD [28]. After a fast

Synthesis of mono-functionalized S-diazocines via intramolecular Baeyer–Mills reactions

• Miriam Schehr,
• Daniel Hugenbusch,
• Tobias Moje,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2018, 14, 2799–2804, doi:10.3762/bjoc.14.257

• benzyl bromides 8–11, which were commercially available or synthesized by radical bromination. The S-diazocines precursors 13–16 were then subjected to the intramolecular Baeyer–Mills reaction yielding the S-diazocines 1–4. In the first step the nitro group was reduced with zinc powder to the

Non-metal-templated approaches to bis(borane) derivatives of macrocyclic dibridgehead diphosphines via alkene metathesis

• Tobias Fiedler,
• Michał Barbasiewicz,
• Michael Stollenz and
• John A. Gladysz

Beilstein J. Org. Chem. 2018, 14, 2354–2365, doi:10.3762/bjoc.14.211

• (in,in/out,out)-2·2BH3 (2%). Four of these structures are verified by independent syntheses. Second, 1,14-tetradecanedioic acid is converted (reduction, bromination, Arbuzov reaction, LiAlH4) to H2P((CH2)14)PH2 (10; 76% overall yield). The reaction with H3B·SMe2 gives 10·2BH3, which is treated with n

Recent advances in hypervalent iodine(III)-catalyzed functionalization of alkenes

• Xiang Li,
• Pinhong Chen and
• Guosheng Liu

Beilstein J. Org. Chem. 2018, 14, 1813–1825, doi:10.3762/bjoc.14.154

• -disubstituted-α-hydroxy-carboxylamides, was disclosed by Gulder and co-workers [76]. This catalytic system was applied to the bromination of alkenes by Gulder and co-workers. For example, the iodine(III)-catalyzed halocyclization of methacrylamide 68 generated the brominated oxindole 69 (Scheme 20) [77]. In

• ]. Oxyarylation of alkenes [71]. Asymmetric oxidative rearrangements of alkenes [72]. Bromolactonization of alkenes [75]. Bromination of alkenes [77][78]. Cooperative strategy for the carbonylation of alkenes [79]. Acknowledgements We are grateful for financial support from the National Nature Science Foundation

Enantioselective phase-transfer catalyzed alkylation of 1-methyl-7-methoxy-2-tetralone: an effective route to dezocine

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 1421–1427, doi:10.3762/bjoc.14.119

• with allyl or propargyl bromide to obtain C12 and C13. In another way, cinchonidine was reduced by H2/Pd/C to yield dihydrocinchonidine, and then reacted with 4-trifluoromethylbenzyl bromide to obtained C14. C15 was prepared from cinchonidine via bromination, debromination and condensation with 4

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

• (Scheme 8). After bromination of 40 with molecular bromine in carbon tetrachloride, direct dehydrobromination with lithium chloride in dimethylformamide gave 11 in 85% isolated yield. Müller’s group reported an alternative synthesis for 11 starting from the carbene adduct 41 over two or three steps [55

• benzotropylium ion 45. Secondly, 11 is obtained in 18% yield after benzylic bromination of 42 with NBS, followed by in situ elimination reaction of the labile bromide 43 mediated by t-BuOK (Scheme 9). Palladium-catalyzed C–C bond-formation reactions such as Heck and Sonogashira couplings are employed in a wide

• method for the synthesis of 2,3-benzotropone (12) starting with 1-benzosuberone (162) (Scheme 29) [134]. First, the unsaturated ketone 163, which is called Julia’s ketone, was prepared by NBS-bromination in the presence of a trace of benzoyl peroxide (BPO) and followed by dehydrobromination. Another