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

• pyridazine-bridged, and bis-nickel as well as bis-palladium pyrazole-bridged complexes were obtained. Keywords: bimetallic complexes; bisoxazolines; chiral ligands; heterocycles; Introduction Metal-centered asymmetric catalysis most commonly relies on monometallic complexes of various chiral ligands, among

• was reported to form a bis-palladium complex with one equivalent of [(η3-C3H3)PdCl]2 [51]. Little is known about the complexing abilities of compounds 9 and 11 [49][52]. The naphthyridine-based ligand 10 forms a dinuclear complex with nickel(ΙΙ) acetate (Ni∙∙∙Ni distance = 3.132 Å). Compound 12

Synthesis of new p-tert-butylcalix[4]arene-based polyammonium triazolyl amphiphiles and their binding with nucleoside phosphates

• Vladimir A. Burilov,
• Guzaliya A. Fatikhova,
• Mariya N. Dokuchaeva,
• Ramil I. Nugmanov,
• Diana A. Mironova,
• Pavel V. Dorovatovskii,
• Victor N. Khrustalev,
• Svetlana E. Solovieva and
• Igor S. Antipin

Beilstein J. Org. Chem. 2018, 14, 1980–1993, doi:10.3762/bjoc.14.173

• instead of pyrophoric Raney nickel. Finally, a diazotization procedure with subsequent azide substitution [37][38] gave calix[4]arene azide derivatives 4 and 8. For the latter reaction a mixture of DMF/glacial acetic acid 3:1 was found to be the optimal solvent. The structures of macrocycles 4 and 8 were

Cobalt–metalloid alloys for electrochemical oxidation of 5-hydroxymethylfurfural as an alternative anode reaction in lieu of oxygen evolution during water splitting

• Jonas Weidner,
• Stefan Barwe,
• Kirill Sliozberg,
• Stefan Piontek,
• Justus Masa,
• Ulf-Peter Apfel and
• Wolfgang Schuhmann

Beilstein J. Org. Chem. 2018, 14, 1436–1445, doi:10.3762/bjoc.14.121

• with the same electrode. Electrolysis of HMF using a CoB modified nickel foam electrode at 1.45 V vs RHE achieved close to 100% selective conversion of HMF to FDCA at 100% faradaic efficiency. Keywords: alternative anode reaction; electrocatalysis; electrosynthesis; HMF oxidation; hydrogen evolution

• ]. Here, HMF was selectively converted to FDCA in NaOH (1.0 M) as electrolyte using a nickel oxide/hydroxide anode achieving a yield of 71% [25]. Strasser and Vuyyuru observed the degradation of HMF to humin type products in highly alkaline solutions and proposed a lower working pH value (<13) for

• [4]. The elaborate separation of TEMPO from FDCA appeared to be an additional disadvantage [24]. Recently, Sun and co-workers reported the electrochemical oxidation of HMF using various non-precious cobalt and nickel based bifunctional HER/OER water splitting electrocatalysts, namely CoP on copper

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

• complex to promote the enantioselective addition of methanol to N-Boc-isatin imines 3 [79]. As shown in Scheme 20, the use of a chiral nickel catalyst in situ generated from NiCl2 and the chiral bis(imidazolidine)pyridine ligand 56 promoted this reaction in toluene at room temperature in the presence of a

• enantioselectivities (up to 94% ee) by using chiral nickel and palladium complexes with imidazoline and pyridine-oxazoline ligands while the first additions of enaminones to isatin imines catalyzed by chiral phosphoric acids provided even higher enantioselectivities (up to 97% ee). In spite of these significant

• cinchona alkaloid-derived thiourea. Aza-Henry reaction of N-Boc-isatin imines with nitromethane catalyzed by a bifunctional guanidine. Domino addition/cyclization reaction of N-Boc-isatin imines with 1,4-dithiane-2,5-diol (53) catalyzed by a tertiary amine-squaramide. Nickel-catalyzed additions of methanol

High-yielding continuous-flow synthesis of antimalarial drug hydroxychloroquine

• Eric Yu,
• Hari P. R. Mangunuru,
• Nakul S. Telang,
• Caleb J. Kong,
• Jenson Verghese,
• Stanley E. Gilliland III,
• Saeed Ahmad,
• Raymond N. Dominey and
• B. Frank Gupton

Beilstein J. Org. Chem. 2018, 14, 583–592, doi:10.3762/bjoc.14.45

• prepare compound 6. It is well known that the direct one-step reductive amination of 6 to give 12 can be accomplished by simple heterogeneous reduction with H2/Raney-nickel [24]. However, THF is employed in all of our prior flow steps and is a poor choice as a solvent for the reductive amination step due

• to limited solubility of ammonia in THF. H2/Raney-nickel reductions are often carried out in alcoholic media where much higher concentrations of ammonia are achievable but would require a solvent exchange. There are many reports of continuous-flow chemistry methods for reductive amination of ketones

• heterogeneous reduction with H2/Raney-nickel. Therefore, we explored an alternate strategy: simple conversion of the ketone group of 6 to oxime 11, followed by reduction to give 5-(ethyl(2-hydroxyethyl)amino)-2-aminopentane (12). We have found H2/Raney-nickel efficiently reduces 11 to 12 with THF as the solvent

An alternative to hydrogenation processes. Electrocatalytic hydrogenation of benzophenone

• Cristina Mozo Mulero,
• Alfonso Sáez,
• Jesús Iniesta and
• Vicente Montiel

Beilstein J. Org. Chem. 2018, 14, 537–546, doi:10.3762/bjoc.14.40

• important to note that, formation of “active hydrogen” is the main step in this process and hydrogen-active powder electrocatalysts such as Pd/C, Pt/C or Raney-nickel have been demonstrated as the optimal choice [16][17]. Moreover, the organic molecule adsorption rate must be faster than that one associated

Latest development in the synthesis of ursodeoxycholic acid (UDCA): a critical review

• Fabio Tonin and
• Isabel W. C. E. Arends

Beilstein J. Org. Chem. 2018, 14, 470–483, doi:10.3762/bjoc.14.33

• mechanism for this step is analogous to the mechanism for ketal or acetal formation except sulphur replaces oxygen as the nucleophile attacking the carbonyl group. In a second step, the dithioketal is reduced to the corresponding methylene compound by hydrogenolysis in presence of Raney Nickel (actually

Continuous-flow retro-Diels–Alder reaction: an efficient method for the preparation of pyrimidinone derivatives

• Imane Nekkaa,
• Márta Palkó,
• István M. Mándity and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2018, 14, 318–324, doi:10.3762/bjoc.14.20

• the literature, a similar desulfurisation batch reaction was performed with nickel catalysis, in ethanol (EtOH)/water (2:1) solution [55][56][57]. Thus, thioxo derivative 8b was dissolved in this mixture, and the CF method was repeated. Desulfurisation of 8b, at 250 °C without adding any catalytic

• metal, provided tricyclic 15b in good yield (90%). Most probably, the reaction was catalyzed by nickel, a component of the 304 stainless steel reactor coil [58][59]. These results also underline the importance to select appropriate solvents and tubing [60][61] for thermally driven reactions. In support

The use of 4,4,4-trifluorothreonine to stabilize extended peptide structures and mimic β-strands

• Yaochun Xu,
• Isabelle Correia,
• Tap Ha-Duong,
• Nadjib Kihal,
• Jean-Louis Soulier,
• Julia Kaffy,
• Benoît Crousse,
• Olivier Lequin and
• Sandrine Ongeri

Beilstein J. Org. Chem. 2017, 13, 2842–2853, doi:10.3762/bjoc.13.276

• in good yield starting from the N-benzylation of L-proline in the presence of KOH, then activation of the carboxylic acid functionality of 10 using SOCl2 at low temperature, followed by condensation with 2-aminobenzophenone (Scheme 2). Complexation of 11 with nickel nitrate and glycine under basic

• conditions gave the nickel Schiff base complex 12 in 71% yield as red crystals. The nucleophilic glycine equivalent 12 went through the aldol reaction with trifluoroacetaldehyde to give complex 13 in moderate yield (66%). Further hydrolysis of complex 13 led to the recovery of the chiral auxiliary 11 and

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

• sensors [51]. Due to the strong electronegativity of fluorine, the acidity of these pyrrole rings is increased in TFEO-H2Pc. For this reason, it is susceptible to deprotonation, whereas protonation hardly occurs. Trifluoroethoxy-substituted nickel phthalocyanine (TFEO-NiPc) and trifluoroethoxy-substituted

Phosphonic acid: preparation and applications

• Charlotte M. Sevrain,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2017, 13, 2186–2213, doi:10.3762/bjoc.13.219

• 14, Figure 4), was assessed to complex indium [86] or terbium [87] with the aim to develop bone targeting and dosimetry. It was also employed to complex 89Y and applied as pH sensitive NMR probe [88], or as organic precursor of crystalline manganese, nickel [89] or lanthanide-containing hybrid

Synthesis of 2-aminosuberic acid derivatives as components of some histone deacetylase inhibiting cyclic tetrapeptides

• Shital Kumar Chattopadhyay,
• Suman Sil and
• Jyoti Prasad Mukherjee

Beilstein J. Org. Chem. 2017, 13, 2153–2156, doi:10.3762/bjoc.13.214

• chiral nickel complex among others. Moreover, many of these studies have also reported an elegant use of this unsaturated amino acid [19]. Our simple protocol involves the use of less sophisticated reagents and catalysts and the use of easily available starting materials; it proceeds in an overall yield

Solvent-free sonochemistry: Sonochemical organic synthesis in the absence of a liquid medium

• Deborah E. Crawford

Beilstein J. Org. Chem. 2017, 13, 1850–1856, doi:10.3762/bjoc.13.179

• ]. Metal catalysts are prepared by the sonication of metal halides (e.g., Pt and Pd – reduction of metal) in the presence of Li and THF [14][15]. Furthermore, the catalytic behaviour of catalysts such as Raney Nickel, has reportedly been increased solely due to the effect of using ultrasound [16]. Catalyst

Pd(OAc)₂/Ph₃P-catalyzed dimerization of isoprene and synthesis of monoterpenic heterocycles

• Dominik Kellner,
• Maximilian Weger,
• Andrea Gini and
• Olga García Mancheño

Beilstein J. Org. Chem. 2017, 13, 1807–1815, doi:10.3762/bjoc.13.175

• , titanium-, zirconium-, iron-, cobalt-, vanadium- or aluminum-based Ziegler-type catalysts lead mostly to the linear tail-to-head 2-TH dimer 2,6-dimethyl-1,3,6-octatriene (alloocimene) [27], and the use of nickel catalysts allows the preparation of the tail-to-tail dimer 2-TT (2,7-dimethyl-1,3,7-octatriene

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

• , Jadavpur, Kolkata 700032, India. Fax: +91 33 24730957; Tel: +91 33 23223403 10.3762/bjoc.13.174 Abstract The present work demonstrates the C–S cross-coupling reaction between aryl halides and thiols using nickel nanoparticles (Ni NPs) supported on reduced graphene oxide (Ni/RGO) as a heterogeneous

• first palladium-catalyzed arylation of thiols was reported by Migita and co-workers in 1980 [5], and soon after Cristau and co-workers developed a nickel-catalyzed route for C–S cross-coupling reactions [6]. Other metals such as copper [7], cobalt [8], iron [9], rhodium [10], manganese [11], indium [12

• peak related to the nickel oxide (NiO). The intensity ratio of the D over the G band was found to be 1.03, which is similar to that of Ni/RGO-40 before used in the C−S coupling reaction (Figure 2a). The powder XRD of Ni/RGO-40, recovered after the first cycle, was also recorded and is shown in Figure 3

Phosphazene-catalyzed desymmetrization of cyclohexadienones by dithiane addition

• Matthew A. Horwitz,
• Elisabetta Massolo and
• Jeffrey S. Johnson

Beilstein J. Org. Chem. 2017, 13, 762–767, doi:10.3762/bjoc.13.75

• of the dithiane moiety via Raney nickel-promoted desulfurization (Scheme 5). To observe any substrate conversion, it was necessary to use a hydrogen atmosphere. Under those conditions, though the dithiane function was removed, degradation occurred. Conclusion In conclusion, we have developed a

• tethered nucleophile. Scope of the transformation. Convex facial additions. Attempted oxidative deacylation. Attempted desulfurization with Raney nickel. Carbonyl deprotection conditions. Supporting Information Supporting Information File 247: Experimental procedures, characterization data and copies of

Fluorinated cyclohexanes: Synthesis of amine building blocks of the all-cis 2,3,5,6-tetrafluorocyclohexylamine motif

• Tetiana Bykova,
• Nawaf Al-Maharik,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2017, 13, 728–733, doi:10.3762/bjoc.13.72

• formamide 12 in 78% yield, a compound also confirmed by X-ray crystallography [20]. Ultimately treatment of nitrile 11a with nickel boride generated in situ from nickel chloride and sodium borohydride, resulted in its full reduction to amine 5a in 50% yield (Scheme 2) [21][22]. The analogous protocol was

• nickel boride delivered amine 5b in 65% yield as a crystalline solid and an analogous reduction of 11c generated the racemic amine 5c as a colourless liquid. The structure of 11b was confirmed by X-ray structure analysis (Scheme 3). Amines 5a and 5b were reacted with terephthaloyl chloride as a means of

Conjecture and hypothesis: The importance of reality checks

• David Deamer

Beilstein J. Org. Chem. 2017, 13, 620–624, doi:10.3762/bjoc.13.60

• universal common ancestor (LUCA) may have originated in hydrothermal vents. The iron-sulfur chemistry proposed for hydrothermal vents was tested by Huber and Wächtershäuser [15][16] who simulated vent conditions with boiling mixtures of iron and nickel sulfides to which various reactants were added. They

• vent conditions by injecting a solution of potassium phosphate, sodium silicate and sodium sulfide (pH 11) into a second solution of ferrous chloride, sodium bicarbonate and nickel chloride (pH 5). The aim was to determine whether carbon dioxide (present as 10 mM sodium bicarbonate) can be reduced

Transition-metal-catalyzed synthesis of phenols and aryl thiols

• Yajun Liu,
• Shasha Liu and
• Yan Xiao

Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58

• succeeded in a Nickel catalyzed thiolation of aryl iodides with thiourea in DMF. Aryl iodides firstly reacted with thiourea in the presence of bis(triethylphosphine)nickel(II) chloride and sodium cyanoborohydride as catalyst precusor, and afforded aryl isothiuronium iodide, which could be further converted

Effect of the ortho-hydroxy group of salicylaldehyde in the A³ coupling reaction: A metal-catalyst-free synthesis of propargylamine

• Sujit Ghosh,
• Kinkar Biswas,
• Suchandra Bhattacharya,
• Pranab Ghosh and
• Basudeb Basu

Beilstein J. Org. Chem. 2017, 13, 552–557, doi:10.3762/bjoc.13.53

• known as A3 coupling reaction, remains the most common and straightforward method for the synthesis of propargylamine. The A3 coupling reaction is reported under transition-metal-catalyzed conditions using copper [12][17][18][19], gold [17][20][21], silver [17][22], zinc [17][23], nickel [24], iron [25

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• using lithium, nickel and palladium catalysts (Scheme 15). A general mechanism illustrating the role of transition metal complexes and CO in this reaction is shown in Scheme 15. Cyclic esters were also used in the syntheses of 1-indanones. Thus, by adding β-propiolactone to aluminum chloride in benzene

• obtained from the reaction of o-phthalaldehyde (86) with acetophenone 87 (Scheme 28). Iron(III) complexes of 88a–d turned out to be promising candidates for potential photovoltaic or luminescence applications. An intramolecular hydroacylation, catalyzed by nickel(0)/N-heterocyclic carbenes leading to the

• ., cyclopentenone 239) with alkynes in the presence of nickel and aluminum complexes [108]. This [2 + 2 + 2] cycloaddition run with a high regioselectivity and led mostly to meta isomers. The authors used, as catalytic systems, the following complexes: Ni(acac)2, Ni(cod)2, Me3Al, Me2Al(OPh), MeAl(OPh)2 and Al(OPh)3

The reductive decyanation reaction: an overview and recent developments

• Jean-Marc R. Mattalia

Beilstein J. Org. Chem. 2017, 13, 267–284, doi:10.3762/bjoc.13.30

• charge on the carbon adjacent to the cyano group [76][77]. Transition-metal-catalyzed reductive decyanation Hydrogenation of α-aminonitriles The decyanation of α-aminonitriles with hydrogen present in an excess of Raney nickel was described by Husson and co-workers on oxazolidine derivatives [83][84

• ]. The authors logically proposed that the decyanation occurred via the reduction of an iminium ion intermediate. The hydrogenation of α-aminonitriles catalyzed by nickel nanoparticles results in reductive decyanation and yields 29–31. The colloid solution of nickel is prepared in situ via reduction of

• alkyl cyanides lead to a complex mixture. Nickel-catalyzed reductive decyanation Maiti et al. established that the Ni(acac)2 complex (acac = acetylacetonate) of PCy3 (Cy, cyclohexyl) in combination with TMDS (tetramethyldisiloxane) as hydride source can catalyze the reductive decyanation efficiently

Extrusion – back to the future: Using an established technique to reform automated chemical synthesis

• Deborah E. Crawford

Beilstein J. Org. Chem. 2017, 13, 65–75, doi:10.3762/bjoc.13.9

• prepared in batch. PXRD analysis also indicated that highly crystalline materials were produced from the extrusion process, prior to any post process purification [2]. Two discrete metal complexes have been synthesised by extrusion, involving the reaction between salenH2 and nickel acetate dihydrate as

• well as the reaction between triphenylphosphine and nickel thiocyanate, both in the presence of stoichiometric amounts of MeOH (Figure 6) [2]. High-quality products were obtained, as determined by 1H NMR spectroscopy, PXRD analysis (which gave sharp diffraction patterns, indicating high crystallinity

From betaines to anionic N-heterocyclic carbenes. Borane, gold, rhodium, and nickel complexes starting from an imidazoliumphenolate and its carbene tautomer

• Ming Liu,
• Jan C. Namyslo,
• Martin Nieger,
• Mika Polamo and
• Andreas Schmidt

Beilstein J. Org. Chem. 2016, 12, 2673–2681, doi:10.3762/bjoc.12.264

• taken in the anion detection mode show the peak of 10 as base peak at m/z = 627. The anionic N-heterocyclic carbene 7 also forms a rhodium and a nickel complex (Scheme 2). The colorless rhodium complex [Rh(7)3] 11 was prepared on reaction of the tautomeric mixture 6A/B with either chlorido(1,5

• the determined dihedral angles for C1–N2–C10–C15, C21–N22–C30–C35, and C41–N42–C50–C55 are 26.371(5)°, 18.939(5)°, and −33.008(5)°, respectively. The carbenes are twisted by approximately 28.1° to 37.0° in relation to the Rh–Ccarbene bonds. The reaction of 6A/6B with bis(triphenylphosphine)nickel(II

• ) chloride at reflux temperature resulted in the formation of the nickel complex [Ni(7)2] (12, Scheme 2). Single crystals were obtained by slow evaporation of 12 from EtOAc/MeOH. The X-ray analysis shows two independent nickel complexes which are connected via hydrogen bonds to two water molecules (Figure 5

Facile synthesis of a 3-deazaadenosine phosphoramidite for RNA solid-phase synthesis

• Elisabeth Mairhofer,
• Elisabeth Fuchs and
• Ronald Micura

Beilstein J. Org. Chem. 2016, 12, 2556–2562, doi:10.3762/bjoc.12.250

• . Only when treated with hydrazine, nucleophilic substitution was observed and after reduction with Raney nickel the desired 3-deazaadenosine was isolated. Our own attempts towards direct ammonolysis failed as well. Additionally, the limited commercial availability of hydrazine and its inconvenience in

• . c) Anhydrous hydrazine, steam bath, 1 h, not isolated. d) Raney nickel, water, reflux, 1 h. Synthesis of c3A described by Montgomery et al. in 1977 [23]. The final step, displacement of the 2-chlorine atom by a hydrogen atom, remains problematic [24][25][26]. a) 1,2,3,5-Tetraacetyl-ß-D-ribofuranose