Chiral bisoxazoline ligands designed to stabilize bimetallic complexes

• Deepankar Das,
• Rudrajit Mal,
• Nisha Mittal,
• Zhengbo Zhu,
• Thomas J. Emge and
• Daniel Seidel

Beilstein J. Org. Chem. 2018, 14, 2002–2011, doi:10.3762/bjoc.14.175

• , Florida 32611, USA 10.3762/bjoc.14.175 Abstract Chiral bisoxazoline ligands containing naphthyridine, pyridazine, pyrazole, and phenol bridging units were prepared and shown to form bimetallic complexes with various metal salts. X-ray crystal structures of bis-nickel naphthyridine-bridged, bis-zinc

• -epoxides [16]. Trost et al. disclosed the synthesis of dinuclear zinc complexes 3 and their application to enantioselective Aldol reactions [17][18] and a host of other asymmetric transformations [18]. Other notable contributions in this area were provided by the groups of Martell [19][20], Maruoka [21][22

• ligand with three nitrogen donor atoms per metal center. Ligand 16-H2 was found to undergo complex formation with various copper, zinc, palladium and nickel salts. Figure 3 shows the X-ray crystal structure of 16·Ni2(OAc)2, obtained from ligand 16-H2 and two equivalents of nickel(ΙΙ) acetate. The

Cationic cobalt-catalyzed [1,3]-rearrangement of N-alkoxycarbonyloxyanilines

• Itaru Nakamura,
• Mao Owada,
• Takeru Jo and
• Masahiro Terada

Beilstein J. Org. Chem. 2018, 14, 1972–1979, doi:10.3762/bjoc.14.172

• [13]. A divalent cationic zinc catalyst also promoted the present reaction, albeit with lower chemical yield than Co(II) (Table 1, entries 10 and 11), while the use of Fe(II) and Pd(II) resulted in low chemical yield due to the formation of the para-isomer 3a (Table 1, entries 12 and 13). Indeed the

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• organophosphine was found to have a profound effect on the catalytic activity; some reactions were sluggish when tricyclohexylphosphine or triphenylphosphine were used as catalysts. The tributylphosphine acts as a nucleophilic trigger to attack, and thus initiates the reaction. 3.1.1.3 Use of zinc salts. In

• continuation of their effort to develop a general methodology for the thiolysis of epoxides, Pizzo et al. reported zinc(II) chloride-catalyzed thiolysis of epoxides in water at 30 °C as shown in Scheme 4 [23]. The reaction was compatible with a variety of epoxide substrates such as α- and β-substituted 1,2

• acid catalyzed protocols. Many asymmetric versions of epoxide opening by thiols assisted by chiral catalysts have been reported and are part of several reviews [30][31][32][33][34][35][36]. In 1985, Yamashita and Mukaiyama demonstrated the efficacy of zinc L-tartrate as a heterogeneous chiral Lewis

Synthesis of chiral 3-substituted 3-amino-2-oxindoles through enantioselective catalytic nucleophilic additions to isatin imines

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 1349–1369, doi:10.3762/bjoc.14.114

• aldehydes catalyzed by L-diphenylprolinol trimethylsilyl ether. Addition of dimedone-derived enaminones to N-Boc-isatin imines catalyzed by a phosphoric acid. Addition of hydroxyfuran-2-one-derived enaminones to N-Boc-isatin imines catalyzed by a phosphoric acid. Zinc-catalyzed Mannich reaction of N-Boc

A selective removal of the secondary hydroxy group from ortho-dithioacetal-substituted diarylmethanols

• Anna Czarnecka,
• Emilia Kowalska,
• Agnieszka Bodzioch,
• Joanna Skalik,
• Marek Koprowski,
• Krzysztof Owsianik and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2018, 14, 1229–1237, doi:10.3762/bjoc.14.105

• % yields and is recommended for the substrates containing sulfur atoms, for which transition metal-induced reactions fail. Keywords: diarylmethanes; diarylmethanols; 1,3-dithiane; selective reduction; sodium cyanoborohydride; zinc iodide; Introduction In last decades, diarylmethanes, such as I–IV and

• ortho-1,3-dithianylaryl(aryl)methanols leading to ortho-1,3-dithianylaryl(aryl)methanes using the ZnI2-Na(CN)BH3 reductive system (Scheme 1). The use of zinc iodide is critical in this system. It was used for the first time in dichloroethane by Lau et al. to reduce aryl ketones, aldehydes, benzylic

• -dithianyl derivatives is facilitated by oxophilic zinc which preferentially binds to the OH oxygen atoms (bond dissociation energies for Zn–O and Zn–S are 284 and 205 kJ/mol, respectively) [67]. The weakened C–O bond is thus more susceptible to the borohydride attack to produce the corresponding

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

• ), the corresponding benzyl bromides were mainly obtained along with a small amount of the target C–H acetoxylation product; this byproduct formation might imply the intermediacy of these organic bromides before the production of benzyl acetates. Hence, the reaction system was modified to include zinc(II

• -methoxy-3-thiocyanatobenzene (1f), prepared from 1-ethyl-4-methoxybenzene (1a) through the hypervalent iodine(III)-induced aromatic cation radical coupling with thiocyanate [75][76], similarly acetoxylated under the standard reaction conditions without zinc(II) acetate (Table 2, entry 5). The

• substituents than in other previously described compounds, showing higher reactivity and chemoselectivity of the benzylic position (see ref. [51]). The reactions of substrates 1h–j proceeded without the use of zinc(II) acetate (see Table 2, entries 7–9 versus entry 2). The installation of other carboxylic

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

Development of novel cyclic NGR peptide–daunomycin conjugates with dual targeting property

• Andrea Angelo Pierluigi Tripodi,
• Szilárd Tóth,
• Kata Nóra Enyedi,
• Gitta Schlosser,
• Gergely Szakács and
• Gábor Mező

Beilstein J. Org. Chem. 2018, 14, 911–918, doi:10.3762/bjoc.14.78

• zinc-dependent metalloprotease that functions in cell proliferation, cell migration and angiogenesis [1][3][4]. However, it is known that the Asn-Gly moiety is subject to Asn deamidation through succinimide formation leading to isoaspartic acid (isoAsp, isoD) and aspartic acid derivatives usually in a

Recent developments in the asymmetric Reformatsky-type reaction

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 325–344, doi:10.3762/bjoc.14.21

• -hydroxyalkanoates from the reaction of α-halocarbonyl compounds with aldehydes or ketones in the presence of zinc [1]. Today, the Reformatsky reactions are more generally defined as metal insertion into carbon–halogen bonds which are activated by carbonyl groups or related functions at vicinal or vinylogous

• . Furthermore, the challenging field of catalytic enantioselective (aza)-versions is fast-growing since the discovery that ZnMe2 or ZnEt2 could be used as zinc sources allowing more convenient homogeneous reaction conditions to be used [2][3]. This review collects the important developments in asymmetric

• reactions Intermolecular Reformatsky reactions Chiral β-hydroxyalkanoates constitute key intermediates in the synthesis of biologically active molecules. Diastereoselective zinc-mediated Reformatsky reactions involving either chiral aldehydes or chiral nucleophiles or both of them have been widely applied

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• is accomplished by in situ generated singlet oxygen, which is generated by energy-transfer of the excited state of Eosin Y and only possible under aerobic conditions. The authors also found that zinc acetate is beneficial for the selective oxidation. A series of electron-rich and electron-poor

Aminosugar-based immunomodulator lipid A: synthetic approaches

• Alla Zamyatina

Beilstein J. Org. Chem. 2018, 14, 25–53, doi:10.3762/bjoc.14.3

• the azido function with zinc in acetic acid followed by acylation of the liberated amino group with the long-chain acyloxyacyl fatty acid furnished fully acylated 16. In the next steps, the isopropylidene acetal and anomeric TDS ether were removed by treatment with aqueous TFA and the anomeric

Synthetic mRNA capping

• Fabian Muttach,
• Nils Muthmann and
• Andrea Rentmeister

Beilstein J. Org. Chem. 2017, 13, 2819–2832, doi:10.3762/bjoc.13.274

• nucleophiles such as nucleoside mono-, -di- or -triphosphates and are typically reacted in anhydrous DMF in the presence of zinc chloride. The GMP imidazolide (18) is reacted with m7GDP (17) in the presence of ZnCl2 as catalyst to yield m7GpppG (12) [49]. In the past years, variations of this general synthetic

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation and chlorination. Part 2: Use of CF₃SO₂Cl

• Hélène Chachignon,
• Hélène Guyon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2800–2818, doi:10.3762/bjoc.13.273

• optimisation phase, which was possible to minimise by increasing the catalyst loading (see later in the text for other chlorinations with CF3SO2Cl). Indirectly, CF3SO2Cl intervened in the trifluoromethylation of (hetero)arenes; indeed, when reacted with zinc in water, it afforded the zinc sulfinate salt

Consecutive hydrazino-Ugi-azide reactions: synthesis of acylhydrazines bearing 1,5-disubstituted tetrazoles

• Angélica de Fátima S. Barreto,
• Veronica Alves dos Santos and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2017, 13, 2596–2602, doi:10.3762/bjoc.13.256

• %) in trifluoroethanol (TFE) at room temperature for 24 h. The presence of catalytic amounts of zinc chloride as Lewis acid in this reaction had already been reported to improve the yields [33]. Indeed, initial studies without the catalyst afforded the desired products 10a in only 28% yield (120 °C, 30

A concise flow synthesis of indole-3-carboxylic ester and its derivatisation to an auxin mimic

• Marcus Baumann,
• Ian R. Baxendale and
• Fabien Deplante

Beilstein J. Org. Chem. 2017, 13, 2549–2560, doi:10.3762/bjoc.13.251

• incomplete reduction were obtained in greater amounts as the flow rate was further increased along with an increasing proportion of the hydroxyaminoindole 15. This correlates with previous literature findings employing catalysed hydrogenation [22][23][24][25][26] or stoichiometric metal (zinc or indium

Exploring mechanochemistry to turn organic bio-relevant molecules into metal-organic frameworks: a short review

• Vânia André,
• Sílvia Quaresma,
• João Luís Ferreira da Silva and
• M. Teresa Duarte

Beilstein J. Org. Chem. 2017, 13, 2416–2427, doi:10.3762/bjoc.13.239

• achieve a controlled release of biologically active copper ions and it has shown to be an effective antifungal agent against representative yeast and mold [135]. Friščić et al. also reported the synthesis of coordination polymers and BioMOFs using LAG by grinding together zinc oxide and fumaric acid. In

• this work, they initially obtained four different coordination polymers, depending on the choice of the grinding liquid: anhydrous zinc fumarate (1) when grinding with ethanol or methanol; a dihydrate (1·2H2O) when using a mixture of water and ethanol; a tetrahydrate (1·4H2O) and a pentahydrate (1·5H2O

• ) when grinding with three or four equiv of water, respectively (Figure 4) [136][137]. This method was further applied to the mechanochemical synthesis of porous materials with introduced auxiliary ligands. These would allow for coordination to zinc in order to generate pillared MOFs, that could be used

Solvent-free copper-catalyzed click chemistry for the synthesis of N-heterocyclic hybrids based on quinoline and 1,2,3-triazole

• Martina Tireli,
• Silvija Maračić,
• Stipe Lukin,
• Marina Juribašić Kulcsár,
• Dijana Žilić,
• Mario Cetina,
• Ivan Halasz,
• Silvana Raić-Malić and
• Krunoslav Užarević

Beilstein J. Org. Chem. 2017, 13, 2352–2363, doi:10.3762/bjoc.13.232

• copper and zinc, which is much harder and mechanically more resistant than pure copper. We tested two approaches, one using a completely brass milling assembly (brass milling vessels and balls), while the other combined brass milling balls with polytetrafluoroethylene (PTFE, Teflon) vessels. Surprisingly

Synthesis of ergostane-type brassinosteroids with modifications in ring A

• Vladimir N. Zhabinskii,
• Darya A. Osiyuk,
• Yuri V. Ermolovich,
• Natalia M. Chaschina,
• Tatsiana S. Dalidovich,
• Miroslav Strnad and
• Vladimir A. Khripach

Beilstein J. Org. Chem. 2017, 13, 2326–2331, doi:10.3762/bjoc.13.229

• mesylation of diol 18 produced dimesylate 19, which was treated with zinc dust and sodium iodide in refluxing DMF (Tipson–Cohen reaction [16]) to give, after deacetylation, B-lactone olefin 21 in 96% yield. 2α,3α- and 2β,3β-epoxides of type 4 and 5 Olefins of type 3 are evident intermediates for the

Synthesis and application of trifluoroethoxy-substituted phthalocyanines and subphthalocyanines

• Satoru Mori and
• Norio Shibata

Beilstein J. Org. Chem. 2017, 13, 2273–2296, doi:10.3762/bjoc.13.224

• . Review Properties of trifluoroethoxy-substituted phthalocyanines Research on TFEO-Pc has taken place since the 1990s [42]. The early stages of this research focused on spectroscopic investigations of metal-free phthalocyanine and its zinc complex which showed the most fundamental spectroscopic properties

• among the phthalocyanines [43][44]. Trifluoroethoxy-substituted zinc phthalocyanine (TFEO-ZnPc) shows a very strong absorption peak called the Q band in the longer wavelength region greater than 700 nm. It is red-shifted compared with the unsubstituted phthalocyanine zinc complex due to the influence of

• the other hand, phthalocyanine without any trifluoroethoxy groups such as tert-butyl-substituted zinc phthalocyanine (t-Bu-ZnPc) or perfluorinated zinc phthalocyanine (F-ZnPc), showed low solubility in both forms of CO2 while phthalocyanine with zinc as the central metal tended to have higher

Ni nanoparticles on RGO as reusable heterogeneous catalyst: effect of Ni particle size and intermediate composite structures in C–S cross-coupling reaction

• Debasish Sengupta,
• Koushik Bhowmik,
• Goutam De and
• Basudeb Basu

Beilstein J. Org. Chem. 2017, 13, 1796–1806, doi:10.3762/bjoc.13.174

• the given conditions. However, the cross-coupling of bromoarenes could be performed efficiently in the presence of zinc dust (1 equivalent to the substrate bromoarene) in addition to a catalytic amount of Ni/RGO-40 (Table 2, entries 12 and 13). Although the exact role of zinc is not clearly understood

• presence of zinc. Diiodobenzenes, however, underwent smooth coupling affording the bis-coupled products 3m and 3n as the single products (Table 2, entries 14 and 15). Using aliphatic thiols has also resulted in the formation of unsymmetrical aryl alkyl thioether 3o and 3p in relatively lower yields (75–80

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

Direct catalytic arylation of heteroarenes with meso-bromophenyl-substituted porphyrins

• Alexei N. Kiselev,
• Olga K. Grigorova,
• Alexei D. Averin,
• Sergei A. Syrbu,
• Oskar I. Koifman and
• Irina P. Beletskaya

Beilstein J. Org. Chem. 2017, 13, 1524–1532, doi:10.3762/bjoc.13.152

• Osuka and co-workers. Their research was targeted at the Ir-catalyzed β-borylation of porphyrins and zinc porphyrinates with the purpose of the consequent synthesis of di- and polyporphyrin structures [23][24][25], further direct β-arylation of tetrapyrrolic systems with aryl bromides was developed

• Zinc meso-(4-bromophenyl)porphyrinate (1) was chosen as a model substrate for the investigation of the conditions of the catalytic arylation. The reaction with benzothiazole was first catalyzed with Pd(OAc)2/DavePhos (2-dicyclohexylphosphino-2’-dimethylaminobiphenyl) (20:20 mol %) and carried out in

• isocyanide Pd complex followed by the ring closure [32]; on the other hand, the arylation of benzothiophene in the presence of Pd(OAc)2/PCy3*HBF4/PivOH proceeds in accordance with the concerted metalation–deprotonation mechanism [33][34]. We also investigated the reaction of zinc meso-(3-bromophenyl

Nitration of 5,11-dihydroindolo[3,2-b]carbazoles and synthetic applications of their nitro-substituted derivatives

• Roman A. Irgashev,
• Nikita A. Kazin,
• Gennady L. Rusinov and
• Valery N. Charushin

Beilstein J. Org. Chem. 2017, 13, 1396–1406, doi:10.3762/bjoc.13.136

• formation of mono-nitro derivatives (at C-2 or C-6) from the same indolo[3,2-b]carbazoles has also been observed in several cases. Reduction of 2-nitro and 2,8-dinitro derivatives with zinc powder and hydrochloric acid has afforded 2-amino- and 2,8-diamino-substituted indolo[3,2-b]carbazoles, while

• [8]. In this study, we have realized a convenient synthesis of amino-containing ICZ derivatives, starting from 2,8-dinitro-ICZs 2 and 2-nitro-ICZ compounds 3 (Scheme 3). Indeed, nitro compounds 2a–f and 3a,b can easily be reduced on treatment with an excess of zinc powder and hydrochloric acid in THF

• ). We have obtained unexpected results for the reduction of 6,12-dinitro-ICZs with zinc powder and hydrochloric acid in THF solution. Formal exchange of both nitro groups with hydrogen atoms has proved to occur under these reaction conditions, giving 6,12-unsubstituted ICZs 8a and 8e from the nitro

Total synthesis of elansolids B1 and B2

• Liang-Liang Wang and
• Andreas Kirschning

Beilstein J. Org. Chem. 2017, 13, 1280–1287, doi:10.3762/bjoc.13.124

• ) was the installation of the side chain at C1–C13. The synthesis relied on two consecutive Sonogashira–Hagihara cross-coupling reactions that provided the ene–diyne system (C10–C15) 10 in good yield. However, partial hydrogenation (only the zinc–copper couple worked) furnished the desired (Z,E,Z

A concise and practical stereoselective synthesis of ipragliflozin L-proline

• Shuai Ma,
• Zhenren Liu,
• Jing Pan,
• Shunli Zhang and
• Weicheng Zhou

Beilstein J. Org. Chem. 2017, 13, 1064–1070, doi:10.3762/bjoc.13.105

• 10.3762/bjoc.13.105 Abstract A concise and practical stereoselective synthesis of ipragliflozin L-proline was presented starting from 2-[(5-iodo-2-fluorophenyl)methyl]-1-benzothiophene and 2,3,4,6-tetra-O-pivaloyl-α-D-glucopyranosyl bromide without catalyst via iodine–lithium–zinc exchange. The overall

• equiv 2b gave a good result, the amount of 5” was greatly reduced (Table 1, entry 4), while the content of 5 in the crude product was increased to 68% and the isolated yield was 77.7%. It was presumable that a iodine–lithium–zinc exchange and the transmetalation proceeded better than a bromide–lithium

• –zinc exchange and transmetalation to produce the arylzinc derivative in situ in this reaction. However, further increasing the amount of zinc bromide to 1.0 equiv did not improve the reaction (Table 1, entry 5) and elevation of the reaction temperature to −10 °C (Table 1, entry 6) worsened the reaction