A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• corresponding alcohol 2 with 14.7% optical yield [21]. Control experiments confirmed that the modified electrodes served as chiral inductors (Scheme 1). In 1982, Fujihira and Osa reported the modification of Raney nickel powder electrodes with optically active tartaric acid and used these electrodes for the

• asymmetric hydrogenation of ketones [22]. They showed that upon reduction with Raney nickel powder electrodes modified with (R,R)-(+)-tartaric acid, 2-hexanone 3 was converted to (S)-(+)-2-hexanol 4 with an average optical purity of 4%, whereas Raney nickel powder electrodes modified with (S,S)-(−)-tartaric

• diastereoselective Michael addition reactions [103][104]. The glycine–nickel complex 184 was deprotonated using a radical anion generated from the electrochemical reduction of azobenzene. The anionic Ni complex 185 acted as a good C-nucleophile towards Michael acceptors 186 resulting in diastereoisomeric mixtures of

Fluorinated maleimide-substituted porphyrins and chlorins: synthesis and characterization

• Valentina A. Ol’shevskaya,
• Elena G. Kononova and
• Andrei V. Zaitsev

Beilstein J. Org. Chem. 2019, 15, 2704–2709, doi:10.3762/bjoc.15.263

• 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (1) [35] was used as starting compound. The synthesis includes the metallation of the free base porphyrin 1 with an excess of zinc acetate or nickel acetate resulting in the corresponding porphyrin Zn(II) and Ni(II) complexes 2a [36] and 2b [37], respectively

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• different catalysts, such as palladium, copper, silver, iron, nickel, ruthenium, cobalt, etc. Palladium catalysis Palladium is a member of the nickel triad in the periodic table, and palladium complexes exist in three oxidation states, Pd(0), Pd(II), and Pd(IV). Straightforward interconversion between

• were thus obtained with good enantioselectivity. In the same year, Kim’s group [97] accomplished an efficient enantioselective electrophilic α-fluorination of various α-chloro-β-ketoesters catalyzed by chiral nickel complexes with good enantioselectivity (up to 99% ee). Notably, the chiral nickel

• -diamine complexes are air and moisture-stable (Scheme 49). In 2011, two nickel-catalyzed protocols for the enantioselective α-fluorination of β-ketoesters were reported separately. In van Leeuwen’s reaction, SPANamine derivatives were synthesized and applied as chiral ligands in the asymmetric α

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

• used for functionalization/derivatization reactions compared to MCRs in the syntheses of IPs. The role of lanthanum/scandium/nickel/vanadium in synthetic chemistry The application of scandium complexes in organic chemistry has been very scarce due to their low availability and difficulties in

• –C bond formations, and ring opening reactions [83][84][85][86][87]. Along with these nickel and vanadium were also well known to catalyze a number of organic reactions. Recent reviews published on the catalytic applications of these metals in various forms have underlined the indispensable

• alcohols and asymmetric sulfide oxidation [91]. Diverse reactivity, cost efficiency and variable oxidation state [Ni(0)–Ni(IV)] associated with nickel led to remarkable developments in the field of catalytic applications [68]. Nickel catalysis involved cycloaddition, cyclization, C–H bond functionalization

Superelectrophilic carbocations: preparation and reactions of a substrate with six ionizable groups

• Sean H. Kennedy,
• Makafui Gasonoo and
• Douglas A. Klumpp

Beilstein J. Org. Chem. 2019, 15, 1515–1520, doi:10.3762/bjoc.15.153

• benzaldehyde. A nickel-catalyzed procedure gives the dipyridyl intermediate 7 [13]. This is easily oxidized to the diketone 8 and reaction of this substance with 2-lithiopyridine gives the precursor 9. The diol 9 is a substrate with six ionizable groups. Upon ionization in superacidic CF3SO3H (triflic acid

One-pot activation–alkynylation–cyclization synthesis of 1,5-diacyl-5-hydroxypyrazolines in a consecutive three-component fashion

• Christina Görgen,
• Katharina Boden,
• Guido J. Reiss,
• Walter Frank and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 1360–1370, doi:10.3762/bjoc.15.136

• (Figure 2) [26][27]. In addition, 1-acyl-5-hydroxypyrazolines are bidentate ligands for zinc complexes and by virtue of being ring tautomers of β-enolhydrazones they can also act as tridentate ligands for nickel [28] and tin [29][30] complexes. In contrast, dimethylzinc forms dimeric complexes where the 1

Synthesis of non-racemic 4-nitro-2-sulfonylbutan-1-ones via Ni(II)-catalyzed asymmetric Michael reaction of β-ketosulfones

• Alexander N. Reznikov,
• Anastasiya E. Sibiryakova,
• Marat R. Baimuratov,
• Eugene V. Golovin,
• Victor B. Rybakov and
• Yuri N. Klimochkin

Beilstein J. Org. Chem. 2019, 15, 1289–1297, doi:10.3762/bjoc.15.127

• ; Michael addition; nickel complexes; nitroalkenes; Introduction Sulfones are widely used in organic synthesis, particularly, in various reactions of C–C and C=C-bond formation [1][2][3][4]. The use of sulfones in Julia–Kocienski [1] and Ramberg–Bäcklund reactions [2] made this class of compounds

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• example of a metal-directed self-assembly is shown [44]. The mixing of diacetyl and 2-aminoethanethiol led to a dynamic mixture of products including 1. The square-planar directing metal ion nickel(II) induces the formation of cyclic product 2 through a process called self-sorting [51][52][53

• ]. Subsequently, compound 2 underwent substitution with α,α’-dibromo-o-xylene to create the nickel(II) complex 3 [54]. In 2014, James and co-workers reported a one-pot two-step mechanochemical synthesis of metal complexes 7 (Figure 3). First, the salen-type ligand 6 was synthesized from o-hydroxybenzaldehyde (4

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

• 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

• , 5) were obtained directly from stoichiometric complexation reactions between H2L·6HCl, Zn(OAc)2·2H2O, and the corresponding azobenzene carboxylate ion (prepared in situ from the free acid by deprotonation with NEt3 as a base) in methanol. The green-brown nickel (2, 4, 7 and 9) and red-orange colored

• distance between the two planes through the co-ligands amounts to 3.45 Å. Magnetic properties of nickel complexes The paramagnetic nickel complexes 2, 4, and 7 were further investigated by temperature dependent magnetic susceptibility measurements between 2 and 300 K in an applied external field of 0.5 T

Design, synthesis and spectroscopic properties of crown ether-capped dibenzotetraaza[14]annulenes

• Krzysztof M. Zwoliński and
• Julita Eilmes

Beilstein J. Org. Chem. 2019, 15, 617–622, doi:10.3762/bjoc.15.57

• ], little research has been undertaken regarding DBTAAs functionalized with crown ether moieties (see Figure 1). Kruse and Breitmaier [24] reported annulated DBTAA‘s containing benzo-15-crown-5 scaffolds fused with benzenoid rings of the macrocyclic core. Both nickel(II) and cobalt(II) complexes were

• prepared and their binding properties toward sodium and potassium ions were studied in addition to transition metals. Sakata et al. reported the syntheses and characterization of nickel(II), copper(II) [25] and oxovanadium(IV) [26] complexes of crown ether-annulated DBTAAs, which caused dimerization in the

• presence of alkali metal and ammonium ions. Sakata et al. reported the synthesis of peripherally functionalized DBTAAs with the two benzo-15-crown-5 scaffolds appended to the meso-benzoyl substituents [27]. Both crown ether-capped macrocycles in a form of free base and nickel(II) and cobalt(II) complexes

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

• electroluminescent devices [33]. To address these challenges, we [34] and others [35][36] have synthesized functionalized C3-symmetric molecules containing amino acids and peptides. The Negishi cross coupling [37][38] is a reliable synthetic method, which involves palladium or nickel-catalyzed coupling of organozinc

Thermophilic phosphoribosyltransferases Thermus thermophilus HB27 in nucleotide synthesis

• Ilja V. Fateev,
• Ekaterina V. Sinitsina,
• Aiguzel U. Bikanasova,
• Maria A. Kostromina,
• Elena S. Tuzova,
• Larisa V. Esipova,
• Tatiana I. Muravyova,
• Alexei L. Kayushin,
• Irina D. Konstantinova and
• Roman S. Esipov

Beilstein J. Org. Chem. 2018, 14, 3098–3105, doi:10.3762/bjoc.14.289

• , phenylmethylsulfonyl chloride, magnesium chloride, nickel sulfate, potassium dihydroorthophosphate, Ni-IDA sepharose, 5-phosphoribosyl-α-1-pyrophosphate and all bases (adenine, hypoxanthine, guanine, 2-chloroadenine, etc.) were purchased from Sigma-Aldrich (USA, MO). Bacterial strains: a) E. coli C3030 [MiniF lysY

Synthesis of aryl sulfides via radical–radical cross coupling of electron-rich arenes using visible light photoredox catalysis

• Amrita Das,
• Mitasree Maity,
• Simon Malcherek,
• Burkhard König and
• Julia Rehbein

Beilstein J. Org. Chem. 2018, 14, 2520–2528, doi:10.3762/bjoc.14.228

• triflates [8], and diazonium salts [9]. Typical metals used are palladium [10][11][12][13], copper [14][15][16][17][18][19][20][21], nickel [22][23][24], iron [25][26][27][28][29], cobalt [30][31][32], and rhodium [33][34]. Aryl sulfides are also synthesized by cross coupling of thiols and aryl Grignard

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