Earth-abundant 3d transition metals on the rise in catalysis

• Nikolaos Kaplaneris and
• Lutz Ackermann

Beilstein J. Org. Chem. 2022, 18, 86–88, doi:10.3762/bjoc.18.8

• industries as one of the most powerful methods for molecular assembly. With regard to the cost of goods and the allowance of trace metal impurities in medicinally relevant compounds, 3d transition metal complexes, such as those of iron, copper, cobalt or nickel, represent exciting, more sustainable

Facile and innovative catalytic protocol for intramolecular Friedel–Crafts cyclization of Morita–Baylis–Hillman adducts: Synergistic combination of chiral (salen)chromium(III)/BF₃·OEt₂ catalysis

• Karthikeyan Soundararajan,
• Helen Ratna Monica Jeyarajan,
• Raju Subimol Kamarajapurathu and
• Karthik Krishna Kumar Ayyanoth

Beilstein J. Org. Chem. 2021, 17, 2186–2193, doi:10.3762/bjoc.17.140

• convinced us to explore them as suitable chiral Lewis acid catalysts for the Friedel–Crafts cyclization of MBH adducts. Mononuclear(salen) complexes of aluminium, chromium, manganese and cobalt were chosen and screened for the current investigation. Results and Discussion To evaluate the scope of the

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• ] cyclotrimerization reactions in the presence of nickel and cobalt catalysts [38]. First, they employed diyne 15 in the reaction with a series of alkynes (16) or nitriles (17) bearing a variety of functional groups including alkyl and alkene chains, hydroxy groups, and benzene and pyridine rings, to achieve the

• obtain 2,3- and 2,3,6,7-halogenated anthracenes 26 by using CpCo(CO)2 as catalyst (Scheme 5) [39]. This synthesis started with a cobalt-catalyzed cyclotrimerization of previously prepared bis(propargyl)benzenes 22 and bis(trimethylsilyl)acetylene (23), affording the TMS-substituted cyclotrimerization

• -cyclotrimerization reaction catalyzed by a cobalt/zinc reagent [40]. With regard to substituted anthracenes, this method consisted of a [2 + 2 + 2] cycloaddition reaction of 1,6-diynes 27 with 4-aryl-2-butyn-1-ols 28 (Scheme 6). The authors converted the resulting benzylic alcohols 29 to the corresponding aldehydes

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• most studied metal applied in C–H functionalization methodologies. Cobalt-catalyzed C–H activation Cobalt is a cheap metal that presents powerful colors in its ionic forms and therefore, it has been used as a basic element in ink since ancient periods [171][172]. Cobalt alloys are used in blades [173

• ] and batteries [174]. Due to its accessibility, it is well explored in catalysis for many fields, such as cycloaddition reactions [175], polymerization [176], and C–C cross-coupling methods [177]. Several biologically active compounds have been obtained through cobalt catalysis [178][179][180

• ] including its application in C–H activation reactions [181][182][183][184][185]. The synthesis of biologically important compounds using C–H activation techniques has been described by Ackermann and co-workers in 2019 [186]. In this specific work, a cobalt-Cp* catalyzed C–H alkenylation was performed at the

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

• Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

• protein–ligand binding properties as well as biological activities of small molecules, potentially leading to dramatic increases in potency, and thus has been widely explored in drug discovery [54][55][56]. Late-stage C–H methylation has recently been investigated using iron and cobalt catalysts as

Copper-mediated oxidative C−H/N−H activations with alkynes by removable hydrazides

• Feng Xiong,
• Bo Li,
• Chenrui Yang,
• Liang Zou,
• Wenbo Ma,
• Linghui Gu,
• Ruhuai Mei and
• Lutz Ackermann

Beilstein J. Org. Chem. 2021, 17, 1591–1599, doi:10.3762/bjoc.17.113

• ] auxiliaries (Figure 1a). Besides, the cobalt(II)- [31] or nickel(II)-catalyzed [32][33], pyridine oxide (PyO)-directed tandem alkynylation/annulation was realized by Niu and Song et al., which also provided the 3-methyleneisoindolin-1-one scaffolds (Figure 1b). Notably, a sustainable cupraelectro-catalyzed

• unfortunately proven elusive [35]. 2-(1-Methylhydrazinyl)pyridine (MHP) [36] was identified as a powerful removable bidentate directing group, which found widespread application in various cobalt-catalyzed C−H activations [37][38][39][40]. Thus, our group also accomplished a set of electrochemical cobalt

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• donors) for the hydration of olefins in the presence of cobalt complexes (Scheme 16) [56][57][58]. These findings enabled the application of neutral conditions, instead of the basic ones that employed borohydrides [59][60][61], to generate the metal hydride species, thereby expanding the functional group

• tolerance of these reactions. In the last 20 years, MHAT methodologies for olefin functionalization have once again spread in the synthetic organic chemistry community, primarily influenced by the work of Carreira [62][63][64][65][66], who employed cobalt complexes in olefin hydro-N-functionalization

• on a control experiment with substrate 34 that had a tethered internal olefin and furnished the expected cyclization product 35. This reaction indicated a radical cascade initiated by a hydrogen atom transfer from a cobalt hydride to the terminal olefin of 34, followed by a 5-exo-trig cyclization

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• , glycolysis of PET was performed under microwave heating in the presence of Zn(OAc)2, yielding BHET with an 80% selectivity at 97% conversion due to formation of dimers (Table 2, entry 7) [203][204]. Soluble metal chlorides (zinc, magnesium, iron, zirconium, cobalt, nickel) were also explored as catalysts in

• yields were observed for metallated ILs, while under the same experimental conditions, ZnCl2 gave BHET in ≈70% yield (Table 4, entry 5). Similar results were reported for the bmim2[MCl4] (M = Cr, Fe, Co, Zn, Ni, Cu) catalysts, wherein the cobalt derivative resulted in the best performance (Table 4, entry

A new and efficient methodology for olefin epoxidation catalyzed by supported cobalt nanoparticles

• Lucía Rossi-Fernández,
• Viviana Dorn and
• Gabriel Radivoy

Beilstein J. Org. Chem. 2021, 17, 519–526, doi:10.3762/bjoc.17.46

• Lucia Rossi-Fernandez Viviana Dorn Gabriel Radivoy INQUISUR-CONICET, Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, Bahía Blanca, B8000CPB, Argentina 10.3762/bjoc.17.46 Abstract A new heterogeneous catalytic system consisting of cobalt nanoparticles (CoNPs) supported on

• materials and it could be recovered and reused maintaining its unaltered high activity. Keywords: alkenes; cobalt nanoparticles; epoxides; oxidation; TBHP; Introduction Olefin oxidation reactions are key synthetic transformations in the production of oxygenated chemicals of high interest for both academic

• a variety of alkenes as an interesting heterogeneous system. This cobalt oxide mesoporous nanomaterial showed good activity and selectivity to the epoxide product and could be recovered and reused, but the multistep (not straightforward) synthesis of the catalyst and the use of DMF as the solvent

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• , BF3⋅Et2O, etc.). These cobalt-cluster-stabilized propargylium ions exhibit a surprisingly high thermodynamic stability, comparable to that of triarylmethylcarbenium ions and are readily observable by NMR spectroscopy or isolable as salts with relatively weakly coordinating anions (BF4−, PF6−, etc

Using multiple self-sorting for switching functions in discrete multicomponent systems

• Amit Ghosh and
• Michael Schmittel

Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233

• self-assembly of the triamines 10 and 11 in the presence of the aldehyde 12 and cobalt(II) ions [52]. When all components were mixed in a single reaction vessel, the 1H NMR spectrum indicated the formation of homoleptic as well as heteroleptic species. In the following, they explored the ability of the

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• Tung et al. merged photoredox, cobalt, and amine catalysis towards the synthesis of α-functionalised ketones 21 from tetrahydroisoquinolines (THIQs) 22 and ketones 23 (Scheme 3) [28]. The proposed mechanism involves an oxidative quenching cycle using the [CoIII] catalyst to generate [CoII] and [Ru

• then reduce 3-nitrobenzoic acid to the corresponding aniline 25 to turn over the cobalt cycle. Simultaneously, 23 condenses with the chiral primary amine catalyst 26 to give enamine intermediate 27, which can be intercepted by 24 to generate imine intermediate 28, which is finally hydrolysed to turn

Regioselective cobalt(II)-catalyzed [2 + 3] cycloaddition reaction of fluoroalkylated alkynes with 2-formylphenylboronic acids: easy access to 2-fluoroalkylated indenols

• Tatsuya Kumon,
• Miroku Shimada,
• Jianyan Wu,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2020, 16, 2193–2200, doi:10.3762/bjoc.16.184

• -fluoroalkylated indenols, together with a very small amount of 3-fluoroalkylated indanones as side products. Keywords: [2 + 3] cycloaddition; cobalt catalyst; fluorine-containing; indenols; regioselective; Introduction 2,3-Disubstituted indenol derivatives are important compounds possessing high potential due

• using various fluoroalkylated alkynes with 2-iodoaryl ketones via cobalt-catalyzed carbocyclizations (Scheme 1c) [21]. Although our previous work was practical to produce interesting fluoroalkylated indenol derivatives, some drawbacks still remain unsolved. Initially, the reaction showed a low

• regioselectivity, leading to a mixture of 3-fluoroalkylated and 2-fluoroalkylated indenols, which was difficult to separate. Secondly, a trimer of fluoroalkylated alkynes was obtained as a side product since the cobalt(I) species produced by the cobalt(II)/Zn system worked as a suitable catalyst, leading to the

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• (Figure 14). The Pd(0) species, liberated during the reductive elimination, is reoxidized via electron transfer with O2 playing the role of the terminal oxidant. In 2018, Sundararaju et al. reported the first example of dual catalysis employing cobalt, a non-noble metal, in combination with a

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• between an alkyne, an olefin and carbon monoxide, resulting in the regioselective formation of a cyclopentenone derivative (Scheme 1) [18][19][20][21][22]. This cobalt-mediated reaction was initially discovered by Pauson and Khand in the early 70s [23][24][25] and has since become a powerful

• are poor substrates for the PKR as they are deactivated in the cobalt-complexation step, and the highest yields are usually obtained with terminal alkynes. The scenario is similar in the case of fluorinated substrates, with the intramolecular version being much more developed than the intermolecular

• extrusion of two carbon monoxide ligands from the starting cobalt species, allowing the alkyne group to bind to the cobalt metal centers. The subsequent coordination of the olefin counterpart requires the extrusion of a third carbon monoxide ligand, leading to pentacarbonyl complex II. This highly

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• endocyclic, high stereoselectivity was observed with the formation of trans-products (examples 106c and 108b). The oxidative cyclization of β,γ-unsaturated oximes 109 under the action of molecular oxygen and catalytic amounts of bis(5,5-dimethyl-1-(4-methylpiperazin-1-yl)hexane-1,2,4-trione)cobalt(II) (Co

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• oxidation of 29.1 was achieved using Mes-Acr-Me+ (OD2) and a cobalt cocatalyst, ensuring an efficient dehydrogenation. Various N-heterocycles 29.3 were accessed via a radical cyclization cascade with the alkyne derivatives 29.2. Amidyl radical generation The oxidation of amides is more difficult compared to

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• platform for dual catalysis due to their ability to promote both metallocatalysis and photocatalysis in a one-pot system [36][37][38][39]. Martin and co-workers carried out the C–O bond cleavage of alcohols using a cobalt porphyrin under visible light irradiation and a carbon monoxide atmosphere (Scheme 11

• ) [36]. The authors hypothesized that the C–O bond cleavage could be achieved via cobalt-mediated alcohol carbonylation followed by radical decarboxylation of the alkoxycarbonyl intermediate. In a proof-of-concept study, they proceeded with the carbonylation of 1-phenylethanol using Co(II) tetrakis(4

• tetrahydroquinolines by reductive quenching. Selenylation and thiolation of anilines. NiTPP as photoredox catalyst in oxidative and reductive quenching, in comparison with other photocatalysts. C–O bond cleavage of 1-phenylethanol using a cobalt porphyrin (CoTMPP) under visible light. Hydration of terminal alkynes by

A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions

• Pezhman Shiri and
• Jasem Aboonajmi

Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52

• phenol 8 was generated by the reaction of 2-hydroxybenzaldehyde (5) and o‐phenylenediamine (7) at rt using a cobalt catalyst. In the next step, a benzimidazole-containing aldehyde 9 was obtained by the reaction of 6 with benzimidazole-substituted phenol 8. This ligand was immobilized on propylamine

Synthesis of triphenylene-fused phosphole oxides via C–H functionalizations

• Md. Shafiqur Rahman and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2020, 16, 524–529, doi:10.3762/bjoc.16.48

• via 1,4-cobalt migration. The resulting 7-hydroxybenzo[b]phosphole derivative was used for further π-extension through Suzuki–Miyaura couplings and a Scholl reaction, the latter closing the triphenylene ring. The absorption and emission spectra of the thus-synthesized compounds illustrated their

• characteristics of both triphenylene and benzo[b]phosphole. Results and Discussion The present synthetic study commenced with the recently reported preparation of 7-hydroxybenzo[b]phosphole derivative 3 from 3-(methoxymethoxy)phenylzinc (1), 5-decyne (2), and PhPCl2 in the presence of a cobalt–diphosphine

• catalyst (Scheme 2). This one-pot construction of the benzo[b]phosphole core ensured the preferential phosphole ring closure in proximity of the alkoxy group of the arylzinc reagent 1 (regioselectivity of ≈3:1), presumably due to a secondary interaction between the MOM group and the cobalt catalyst during

Visible-light-induced addition of carboxymethanide to styrene from monochloroacetic acid

• Kaj M. van Vliet,
• Nicole S. van Leeuwen,
• Albert M. Brouwer and
• Bas de Bruin

Beilstein J. Org. Chem. 2020, 16, 398–408, doi:10.3762/bjoc.16.38

• useful for the formation of new C–C bonds. Previous works from our group presented cobalt-catalyzed radical cyclization and carbonylation reactions [12][13][14][15][16]. Photoredox catalysis provides a way to generate radical intermediates from simple organic molecules by single-electron redox processes

Room-temperature Pd/Ag direct arylation enabled by a radical pathway

• Amy L. Mayhugh and
• Christine K. Luscombe

Beilstein J. Org. Chem. 2020, 16, 384–390, doi:10.3762/bjoc.16.36

• . There are limited examples across the aryl C–H functionalization literature indicating a transition metal-catalyzed radical process, limited largely to cobalt catalysis [31][32]. While there are several reports of palladium-catalyzed systems for room-temperature direct arylation (i.e., no directing

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

• benzothiazoles via oxidant-free C–H thiolation: On the other hand, a novel dual photoredox catalytic system of photoredox catalyst 11 and a cobalt catalyst was designed by Wu and Lei for the construction of benzothiazoles [101]. Because of the properties of the photoredox catalyst 11, the reaction was carried

Combination of multicomponent KA² and Pauson–Khand reactions: short synthesis of spirocyclic pyrrolocyclopentenones

• Riccardo Innocenti,
• Elena Lenci,
• Gloria Menchi and
• Andrea Trabocchi

Beilstein J. Org. Chem. 2020, 16, 200–211, doi:10.3762/bjoc.16.23

• different compounds, such as (−)-kainic acid [51][52]. Previous similar approaches reported only planar pyrrolocyclopentenones starting from propargyl alcohol–cobalt complexes and allyl amides [50], or carbohydrate-derived allylpropargylamine [49] (Scheme 1a). Results and Discussion Cyclohexanone (1) and

• ). The acylation of the amino group was found necessary to allow for the cobalt-catalyzed reaction to proceed under a CO atmosphere. This step was also carried out in one pot after the KA2 reaction by diluting with pyridine and adding the acylating reagent, to achieve the corresponding product in

• –Khand reaction (Table 1, entry 13), possibly due to a coordinating effect towards the cobalt catalyst. Such an effect was confirmed when the N-tosylpiperidone was used as the ketone component, as also in this case the presence of the tosyl group impaired the acetylated KA2 adduct from reacting under