Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• and 2e were obtained in moderate yield using 3a as the aryl halide in the Heck reaction. The use of 3b in the Heck reaction resulted in a substantial improvement of yield in the synthesis of 2g but not for 2c. Interchanging the roles by using 5-vinylnicotinamide (5a) or methyl 5-vinylnicotinate (5b

1,2,3-Triazolium macrocycles in supramolecular chemistry

• Mastaneh Safarnejad Shad,
• Pulikkal Veettil Santhini and
• Wim Dehaen

Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211

• synthesized the novel tetra-1,2,3-triazolium zinc porphyrin cage 3 (Figure 4) and have probed its characteristics by using UV–visible spectroscopy, determining the association constants for complex formation in 5% water/acetone. This receptor has shown affinity toward all of the halide ions and especially

• literature there are still challenges to find selective iodide receptors due to its low basicity, large size and low charge density. There is an expectation that the combination of strong hydrogen-bonding sites and a large cavity could cause strong complexation with larger halide ions [55]. In 2016 a

• −, Br− and I− were found as 4.4 × 101 M−1, 1.7 × 101 M−1, 8.5 M−1, respectively. Thus, the interaction of 1,2,3-triazolium CH is decreasing with increasing halide size. Besides, the complexes of halides with the macrocycles were shown to have visible charge-transfer absorptions in the molecular crystals

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

• probably deprotonation of the heterocyclic rings with a base. Moreover, nucleophilic aromatic substitution (SNAr) reactions between an aryl halide and a selenium reagent such as aryl selenide anion or diaryl diselenide for C(Ar)–Se bond formation using a base have been reported [20][21][22]. However, the

Fluorinated azobenzenes as supramolecular halogen-bonding building blocks

• Esther Nieland,
• Oliver Weingart and
• Bernd M. Schmidt

Beilstein J. Org. Chem. 2019, 15, 2013–2019, doi:10.3762/bjoc.15.197

• ][22][23][24]. Huber and co-workers demonstrated the activation of a carbonyl group by halogen bonding, and successfully applied this concept to catalysts for Michael addition reactions [25] and also employed neutral [26], and hypervalent iodolium derivatives as activators in a halide abstraction

Synthesis and anion binding properties of phthalimide-containing corona[6]arenes

• Meng-Di Gu,
• Yao Lu and
• Mei-Xiang Wang

Beilstein J. Org. Chem. 2019, 15, 1976–1983, doi:10.3762/bjoc.15.193

• . Upon complexation with a halide, the planar aromatic ring adopted a heavily pinched boat conformation, a result consistent with theoretical prediction [49]. We also examined the host–guest interaction in solution phase employing NMR and UV–vis spectroscopy and fluorescence technology. Unfortunately

Halide metathesis in overdrive: mechanochemical synthesis of a heterometallic group 1 allyl complex

• Ross F. Koby,
• Nicholas R. Rightmire,
• Nathan D. Schley,
• Timothy P. Hanusa and
• William W. Brennessel

Beilstein J. Org. Chem. 2019, 15, 1856–1863, doi:10.3762/bjoc.15.181

• 14627, USA 10.3762/bjoc.15.181 Abstract As a synthesis technique, halide metathesis (n RM + M'Xn → RnM' + n MX) normally relies for its effectiveness on the favorable formation of a metal halide byproduct (MX), often aided by solubility equilibria in solution. Owing to the lack of significant

• ]∞, enable an otherwise unfavorable halide metathesis to proceed with mechanochemical assistance. From this result, we demonstrate that ball milling and unexpected solid-state effects can permit seemingly unfavored reactions to occur. Keywords: caesium; entropy; intermolecular forces; mechanochemistry

• ; metathesis; potassium; Introduction Halide (or ‘salt’) metathesis is a broadly useful synthetic technique in organometallic chemistry, applicable to elements across the entire periodic table. A typical instance involves the reaction of a metal halide (M'Xn) with an organoalkali metal compound (RM; M = Li

Metal-free mechanochemical oxidations in Ertalyte^® jars

• Andrea Porcheddu,
• Francesco Delogu,
• Lidia De Luca,
• Claudia Fattuoni and
• Evelina Colacino

Beilstein J. Org. Chem. 2019, 15, 1786–1794, doi:10.3762/bjoc.15.172

• citrate) resulted in low alcohol-to-aldehyde conversions (<40%) and promoted, conversely, the formation of significant amounts of olefins (>25%) resulting from halide elimination. Any attempt to lower the amount of the nitrosyl catalyst resulted in a poor conversion (69%, Table 2, entry 5). Once the

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

• halide substituent in the product which was successfully overcome by this protocol along with the synthesis of pyrazines and pyrimidines in high yield (Scheme 3). Furthermore, easy functionalization of the products from the viewpoint of reactive halide made them valuable synthons. Molecular oxygen used

Enantioselective Diels–Alder reaction of anthracene by chiral tritylium catalysis

• Qichao Zhang,
• Jian Lv and
• Sanzhong Luo

Beilstein J. Org. Chem. 2019, 15, 1304–1312, doi:10.3762/bjoc.15.129

• investigated in Lewis acid catalysis over the past decades, a chiral counter anion [34][35] with metal elements as the central atom, however, was seldom reported. Typically, the tritylium salts with weakly coordinating anions can be synthesized through a simple halide abstraction from the trityl halide in the

Bambusuril analogs based on alternating glycoluril and xylylene units

• Tomáš Lízal and
• Vladimír Šindelář

Beilstein J. Org. Chem. 2019, 15, 1268–1274, doi:10.3762/bjoc.15.124

• of one molecule and methine and methylene hydrogen atoms of neighboring macrocycles. Finally, we investigated the affinity of the newly prepared bambusuril analogs 1a and 1b towards anions. The addition of halide anions in form of their tetrabutylammonium salts to the solutions of 1a and 1b did not

Alkylation of lithiated dimethyl tartrate acetonide with unactivated alkyl halides and application to an asymmetric synthesis of the 2,8-dioxabicyclo[3.2.1]octane core of squalestatins/zaragozic acids

• Herman O. Sintim,
• Hamad H. Al Mamari,
• Hasanain A. A. Almohseni,
• Younes Fegheh-Hassanpour and
• David M. Hodgson

Beilstein J. Org. Chem. 2019, 15, 1194–1202, doi:10.3762/bjoc.15.116

• be carried out first, and the isolated monoalkylated material then separately subjected to a second alkylation, allowing warming to ≈−40 °C. Our first synthesis of 6,7-dideoxysqualestatin H5 (DDSQ (2), Figure 1), required extension of the above tartrate alkylation chemistry to a homoallylic halide as

• system, where the corresponding diene 39 was isolated in up to 36% yield. In our earlier studies, typically approximately equimolar quantities of tartrate and alkylating agent were used, but with the halide now being synthetically more valuable, efforts focused on conditions which gave the best yields

Insertion of [1.1.1]propellane into aromatic disulfides

• Robin M. Bär,
• Gregor Heinrich,
• Martin Nieger,
• Olaf Fuhr and
• Stefan Bräse

Beilstein J. Org. Chem. 2019, 15, 1172–1180, doi:10.3762/bjoc.15.114

• nucleophiles also proceeds through a radical mechanism [14][15]. The reaction with alkyl halides, initially described by Michl et al. [16], has recently been further investigated by Anderson et al. (Scheme 1) [17]. Both groups showed that the BCP halide can be lithiated to further modify the products. The

Design of a double-decker coordination cage revisited to make new cages and exemplify ligand isomerism

• Sagarika Samantray,
• Sreenivasulu Bandi and
• Dillip K. Chand

Beilstein J. Org. Chem. 2019, 15, 1129–1140, doi:10.3762/bjoc.15.109

• pushing the conversion towards the formation of 3a (Supporting Information File 1, Figure S50). Prolonged heating could not help because the complex 3a is unstable under such conditions. This provided additional support on the higher stability of 4a as compared to 3a. Halide binding by the cavities of a

• ]. Halide recognition by the complex 4a through anion exchange was studied by portionwise addition of freshly prepared solutions of tetra-n-butylammonium halide, i.e., TBA(X) (where X stands for F−, Cl−, Br− and I−) in four separate experiments using DMSO-d6 as the solvent. The anion exchange processes were

• are provided in Supporting Information File 1, Figures S56–S66. The molecular compositions of the halide encapsulated complexes were confirmed by recording ESIMS data for the systems. The double halide encapsulated complexes 6a and 7a were detected. Also, one of the mixed halide–nitrate encapsulated

Molecular recognition using tetralactam macrocycles with parallel aromatic sidewalls

• Dong-Hao Li and
• Bradley D. Smith

Beilstein J. Org. Chem. 2019, 15, 1086–1095, doi:10.3762/bjoc.15.105

• enables them to be effective hosts for a wide range of guest molecules including organic biscarbonyl derivatives, near-infrared dyes, acenes, precious metal halide complexes, trimethylammonium ion-pairs, and saccharides. Keywords: fluorescent dye; host–guest chemistry; hydrogen bonding; hydrophobic

• flexibility of the macrocyclic tetralactams enables them to be effective hosts for a wide range of guest molecules including organic biscarbonyl derivatives, near-infrared dyes, acenes, precious metal halide complexes, trimethylammonium ion pairs, and saccharides. Because of this versatility, macrocyclic

• (left) with anionic square planar metal halide complexes (right). (b) Solid-state structures of B·AuBr4− (X = CH, Z = t-Bu, left) and C·AuBr4− (X = CH, Z = t-Bu, right). (c) Electrostatic potential maps of the interior surfaces of (left) B and (right) C obtained by DFT calculations at the B3LYP/631G

Halogen bonding and host–guest chemistry between N-alkylammonium resorcinarene halides, diiodoperfluorobutane and neutral guests

• Fangfang Pan,
• Mohadeseh Dashti,
• Michael R. Reynolds,
• Kari Rissanen,
• John F. Trant and
• Ngong Kodiah Beyeh

Beilstein J. Org. Chem. 2019, 15, 947–954, doi:10.3762/bjoc.15.91

• 79.45 Å3 in MeOH@1 and 101.17 Å3 in MeCN@1 (rprobe = 1.2 Å) [34]. The deformation also shifts the relative positions of the N-alkyl “arms” and the halide anions, which additionally change the relative orientation of DIOFB XB donors when directional halogen bonding forms. Two DIOFB linked two MeOH-MeCN@1

• was confirmed from the increase shielding of the guest signals. These results adds to the literature of small organic guest compounds bound by N-alkylammonium resorcinarene halide receptors synergistically via HB and XB interactions. Tetravalent XB acceptor, Hex-NARBr 1, Cy-NARCl 2, divalent XB donor

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

• obtain a polymer with particular properties – polydicyclopentadiene (PDCPD) [8][9]. Cationic polymerization of DCPD takes place with metal-halide-based catalyst systems and organometallic compounds. A number of scientific reports were dedicated to the investigation of DCPD polymerization based on these

Selective benzylic C–H monooxygenation mediated by iodine oxides

• Kelsey B. LaMartina,
• Haley K. Kuck,
• Linda S. Oglesbee,
• Asma Al-Odaini and
• Nicholas C. Boaz

Beilstein J. Org. Chem. 2019, 15, 602–609, doi:10.3762/bjoc.15.55

• functional groups including halide groups, esters, and nitrogen-containing heterocycles, yielding monoxidized acetate products in moderate to good yields. While the reaction conditions were effective in the oxidation of secondary benzylic C–H bonds, the reaction was less effective in the oxidation of primary

Thiol-free chemoenzymatic synthesis of β-ketosulfides

• Adrián A. Heredia,
• Martín G. López-Vidal,
• Marcela Kurina-Sanz,
• Fabricio R. Bisogno and
• Alicia B. Peñéñory

Beilstein J. Org. Chem. 2019, 15, 378–387, doi:10.3762/bjoc.15.34

• benign conditions is highly desirable. Based on our previously developed MCR [43] for the synthesis of enol esters with sulfur-containing substituents, we envisaged a two-step methodology starting from an α-haloketone, a thiocarboxylate and an alkyl (pseudo)halide (Scheme 2). Thus, once the enolester is

• chemoenzymatic synthesis of β-ketosulfides. One-pot two-step preparation of phenacylalkylsulfides. aReaction conditions: i. α-haloketone (0.25 mmol), potassium thioacetate (1.1 equiv), alkyl halide (1.1 equiv) and K2CO3 (2.0 equiv) in 500 µL of DMSO, 5 h at room temperature; ii. 100 mg of CAL-B (Novozyme 435

• ) and 9.5 mL of Tris·HCl buffer (50 mM pH 7.5), 30 °C, 24 h, 250 rpm. bReaction performed using 1.0 g of α-chloroacetophenone, potassium thioacetate (1.1 equiv), alkyl halide (1.1 equiv) and K2CO3 (2.0 equiv) in 5 mL of DMSO, 200 mg of CAL-B and 45 mL of Tris-HCl buffer (50 mM pH 7.5), 24 h at room

Synthesis of C₃-symmetric star-shaped molecules containing α-amino acids and dipeptides via Negishi coupling as a key step

• Sambasivarao Kotha and
• Saidulu Todeti

Beilstein J. Org. Chem. 2019, 15, 371–377, doi:10.3762/bjoc.15.33

• iodo compound 6 was treated with freshly activated Zn in DMF at room temperature to afford the zinc insertion product 7 (Scheme 1) [43]. With the organozinc compound 7 at hand we turned to the synthesis of the halide component for the attempted Negishi coupling. For this 4-iodoacetophenone (8) was

Gold-catalyzed ethylene cyclopropanation

• Silvia G. Rull,
• Andrea Olmos and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2019, 15, 67–71, doi:10.3762/bjoc.15.7

• carbene-transfer reactions [22][23]. Neutral IPrAuCl was not effective (Table 1, entry 4), assessing the need of a cationic, halide-free gold species toward that end. The choice of the halide scavenger is not innocent: on the other hand, it is key for the success of this search. Thus, addition of one

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• [55] (Table 6). The size of the ring formed was found to have a crucial influence on the enantioselectivity of the reaction with the enantiomeric excesses decreasing when passing from five to six and seven-membered rings (Table 6, entries 1, 4 and 7). The use of halide additives such as NaBr and NaI

• was also found to be dependent on the size of the ring formed, affecting both conversions and enantiomeric excesses with controversial results (Table 6). It should be underlined that the ambiguous halide influence constitutes a relevant difference between 164 and 165. In fact, for the latter, the

• employment of halide additives had always a beneficial effect on the enantioselectivity [55]. The product ring size dependence observed in the desymmetrization of 166, 168 and 170 with 164 was explained considering that an NHC rotation is possible during the catalytic cycle and that 166, 168 and 170 should

Photocatalyic Appel reaction enabled by copper-based complexes in continuous flow

• Clémentine Minozzi,
• Jean-Christophe Grenier-Petel,
• Shawn Parisien-Collette and
• Shawn K. Collins

Beilstein J. Org. Chem. 2018, 14, 2730–2736, doi:10.3762/bjoc.14.251

• organic halide from the corresponding alcohol (Figure 1) [6][7]. The Appel reaction is representative of a host of transformations that require stoichiometric reagents to effect a functional group change of an alcohol. In 2011, Stephenson and co-workers reported that photocatalysis could be used to

• promote the alcohol→halide conversion using low catalyst loadings of a ruthenium-based catalyst (Ru(bpy)3Cl2, 1 mol %) in the absence of PPh3 as a reductant (Figure 1) [8]. The method possesses numerous advantages (wide functional group tolerance, no formation of oxidized phosphine byproducts [9][10][11

• ][12][13][14], mild reaction conditions and visible-light irradiation), which should be easily embraced by the synthetic community. To further develop the photochemical alcohol→halide transformation, the use of alternative photocatalysts based upon more abundant metals was envisioned [15][16][17][18

The design and synthesis of an antibacterial phenothiazine–siderophore conjugate

• Abed Tarapdar,
• James K. S. Norris,
• Oliver Sampson,
• Galina Mukamolova and
• James T. Hodgkinson

Beilstein J. Org. Chem. 2018, 14, 2646–2650, doi:10.3762/bjoc.14.242

• . However, as our final conjugate contains an aromatic halide we wanted to avoid hydrogenation as the final step and we instead chose to use the para-methoxybenzyl (PMB) protecting group which can be removed under acidic conditions. PMB-protected benzoic acid building block 7 was prepared following a

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• electrochemical reduction. In addition, the corrin-ring of the B12 derivatives is tolerant to free radicals, as described above. Thus, alkylated complexes have been used for radical-mediated organic synthesis such as halide coupling, alkene coupling, and addition to double bonds [7][26][27]. In particular, the Co

Quinolines from the cyclocondensation of isatoic anhydride with ethyl acetoacetate: preparation of ethyl 4-hydroxy-2-methylquinoline-3-carboxylate and derivatives

• Nicholas G. Jentsch,
• Jared D. Hume,
• Emily B. Crull,
• Samer M. Beauti,
• Amy H. Pham,
• Julie A. Pigza,
• Jacques J. Kessl and
• Matthew G. Donahue

Beilstein J. Org. Chem. 2018, 14, 2529–2536, doi:10.3762/bjoc.14.229

• trituration. The reaction is tolerant to halide substitution at the 6-, 7-, and 8-positions (9b, 9c, 9f, 9h). The unprotected hydroxy group in 9d gave reasonably high yield as did electron-withdrawing nitro groups in the 6- and 7-positions (9e, 9g). The substituted isatoic anhydrides from Scheme 3 were then