Advancements in hydrochlorination of alkenes

• Daniel S. Müller

Beilstein J. Org. Chem. 2024, 20, 787–814, doi:10.3762/bjoc.20.72

• interest as the starting materials are inexpensive bulk chemicals and the reactions can be carried out under air without any particular precautions. Radical hydrochlorination reactions Cobalt and iron-promoted radical hydrochlorination reactions are part of the large family of metal hydride hydrogen atom

• the metal-catalyzed hydrochlorination of alkenes based on MH HAT reactions (Scheme 23) [80]. They discovered that a combination of a cobalt catalyst, a silane, and tosyl chloride promoted the hydrochlorination of terminal unactivated alkenes. The scope of the reaction is relatively broad when

• Syntheses [83]. The proposed catalytic cycle is shown in Figure 7 and involves the following steps. First, a cobalt hydride complex A is formed in situ from Co(II) complex and the silane. Then, regioselective alkene hydrocobaltation takes place. This step is highly regioselective, placing the cobalt atom on

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• decarboxylative cross-coupling (DCC) of NHPI esters with organometallic reagents, resembling classic Kumada, Negishi, and Suzuki couplings, has been enabled by nickel (Ni), cobalt (Co), iron (Fe), and copper (Cu) catalysts [84][85][86][87][88][89][90][91] (Scheme 23A). The typical mechanism begins by

Copper-promoted C5-selective bromination of 8-aminoquinoline amides with alkyl bromides

• Changdong Shao,
• Chen Ma,
• Li Li,
• Jingyi Liu,
• Yanan Shen,
• Chen Chen,
• Qionglin Yang,
• Tianyi Xu,
• Zhengsong Hu,
• Yuhe Kan and
• Tingting Zhang

Beilstein J. Org. Chem. 2024, 20, 155–161, doi:10.3762/bjoc.20.14

• ·H2O (Table 1, entries 2–9). To our delight, copper salts were effective, giving the desired product 3aa in excellent yields of 88–95% (Table 1, entries 7–9). Cuprous salts, cobalt chloride, and nickel acetate were partially efficient for the reaction, providing product 3aa in 85% yield (Table 1

Biphenylene-containing polycyclic conjugated compounds

• Cagatay Dengiz

Beilstein J. Org. Chem. 2023, 19, 1895–1911, doi:10.3762/bjoc.19.141

• 2,2'-dihalogenated biphenyls 4 as starting materials [24][25]. Although the cobalt-mediated alkyne trimerization route frequently used by Vollhardt and co-workers is not the first choice for the synthesis of the biphenylene itself, it has led to the synthesis of structurally demanding substituted

• biphenylenes and the emergence of a family of polycyclic hydrocarbons called [N]phenylenes. The utilization of cobalt-mediated alkyne trimerization facilitated the synthesis of [N]phenylenes exhibiting diverse structural configurations, including linear 7, angular 8, zig-zag 9, bent 10, branched 11, and cyclic

• steps (Scheme 15). The initial step involved the synthesis of compound 71 in 64% yield using a cobalt-catalyzed cyclotrimerization reaction between 1,2-diethynylbenzene (5) and bis(trimethylsilyl)acetylene (70), a method commonly employed in [N]phenylene synthesis. Subsequently, treatment of compound 71

Selectivity control towards CO versus H₂ for photo-driven CO₂ reduction with a novel Co(II) catalyst

• Lisa-Lou Gracia,
• Philip Henkel,
• Olaf Fuhr and
• Claudia Bizzarri

Beilstein J. Org. Chem. 2023, 19, 1766–1775, doi:10.3762/bjoc.19.129

• concentration of this greenhouse gas by upcycling. Selectivity towards CO2-reduction products is highly desirable, although it can be challenging to achieve since the metal-hydrides formation is sometimes favored and leads to H2 evolution. In this work, we designed a cobalt-based catalyst, and we present herein

• selectivity from 6% to 97% after four hours of irradiation at 420 nm. Further efficiency enhancement was achieved by adding 1,1,1,3,3,3-hexafluoropropan-2-ol, producing CO with a TON up to 230, although at the expense of selectivity (54%). Keywords: carbon monoxide selectivity; cobalt(II) complex; copper(I

• [19][20][21], cobalt [22][23], and nickel [24][25], have been designed as CO2 reduction catalysts. This (supra)molecular approach is appealing for gaining a structure–property understanding with the goal of tunable and efficient activity. Among the 3d transition metals, cobalt is relatively abundant

Tying a knot between crown ethers and porphyrins

• Maksym Matviyishyn and
• Bartosz Szyszko

Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120

• of coordination compounds of copper(II), iron(II/III), manganese(II), nickel(II), and cobalt(II) with 9-Zn and 9-Cu was demonstrated. The emission quenching was rationalised considering the binding of the transition metal within the crown ether cavity. No quenching was observed upon the addition of

• precursor for coordination compounds. The following transmetallation with cobalt(II) produced an intriguing Pacman-like coordination compound 16-Co(II) (Scheme 6) [66]. The spontaneous oxidation of cobalt(II) to cobalt(III) resulted in modifying the cobalt cation coordination sphere from a distorted-square

• , accommodating the axially-positioned water molecule on the cobalt(III) centre. The latter assembled into a remarkable hexagonal wheel architecture when exposed to air in THF, as evidenced by XRD (Figure 12). The hexagonal wheel [16-Co(III)]6 was stabilised by intramolecular hydrogen bonding between the water

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• -(arylsulfenyl)succinimide 1 (Scheme 27) [62]. The reaction involves the formation of active cobalt species I from the interaction of KOAc with the cobalt pre-catalyst. Treatment of I with 63 resulted in the five-membered cobaltocycle complex II. Next, coordination of 1 to II gave III, followed by intramolecular

• nucleophilic trapping of the electrophilic SAr unit to furnish C2-sulfenylated product 65 and Co-complex IV. At last, active cobalt species I regenerated from IV in the presence of AcOH. It should be noted that when R = H, C2-sulfenylated product 65 may be sulfenylated via a thermal electrophilic aromatic

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

•  27) [88]. This route provides an environmentally friendly and practical approach to alkyl-substituted alkynes. Co-catalyzed reactions In recent years, cobalt has exhibited great application potential as a cross-dehydrogenation coupling catalyst due to its low price, environmentally friendliness, and

• unique catalytic behavior [89]. However, there are only a few examples of cobalt catalysis in CDC reactions. Limited by the activity of Co catalysts, there are few examples of Co-catalyzed reactions involving ether C(sp3)–H bond activation. The Co-catalyzed C(sp3)–C(sp3) CDC of glycine and peptide

• derivatives with THF was developed by Correa et al. (Scheme 28) [90]. This study presents a cost-effective cobalt-catalyzed C(sp3)–H functionalization strategy for α-aminocarbonyl compounds. The method allows for the direct introduction of ethers into a diverse range of glycine derivatives. Importantly, the

Radical ligand transfer: a general strategy for radical functionalization

• David T. Nemoto Jr,
• Kang-Jie Bian,
• Shih-Chieh Kao and
• Julian G. West

Beilstein J. Org. Chem. 2023, 19, 1225–1233, doi:10.3762/bjoc.19.90

• much more efficiently in decarboxylative RLT reactions than aliphatic acids [42]. Outside of decarboxylation, X. Peter Zhang recently reported the enantioselective synthesis of allylic amines through coupled HAT and RLT on allylic C–H bonds [45], using a bulky cobalt porphyrin complex developed and

Enabling artificial photosynthesis systems with molecular recycling: A review of photo- and electrochemical methods for regenerating organic sacrificial electron donors

• Grace A. Lowe

Beilstein J. Org. Chem. 2023, 19, 1198–1215, doi:10.3762/bjoc.19.88

• , inorganic Z-schemes have used cobalt complexes and polyoxometalates to shuttle electrons between water oxidation and carbon dioxide reduction photocatalysts [2][4]. However, the photocatalysts of these systems are usually first developed separately with sacrificial electron donors. Other methods for

• employ redox mediators can use compounds such as cobalt bipyridine complexes which undergo fast reversible electron transfer reactions [2][4][8]. Z-schemes require a steady state concentration of both oxidized and reduced redox mediator species to allow an efficient shuttling of electrons between

• tris buffer rather than phosphate [44]. Instead of using the regenerated NADH in a photocatalytic system, this team actually used an enzyme to consume the regenerated NADH and check its viability. Robert and co-workers recycled the NADH analogue 1,4-BNAH using different photosensitizers and cobalt

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• aromatization steps led to product 43 upon catalyst regeneration. Recently, Ryabchuk et al. [74] used the 3d-metal cobalt catalyst Co/NGr-C@SiO2-L under solvent-free conditions to synthesize various N-aryl-substituted pyrroles 45 in 50–88% yields from the corresponding nitroarenes 44 via the Clauson–Kaas

• reaction involving benign reducing agents H2 or HCOOH or CO/H2O mixtures (Scheme 21). The main advantage of this heterogeneous Co catalyst is that it can be used up to 10 times without significant loss of activity and the active cobalt hydride species selectively reduces nitroarenes to their corresponding

Strategies in the synthesis of dibenzo[b,f]heteropines

• David I. H. Maier,
• Barend C. B. Bezuidenhoudt and
• Charlene Marais

Beilstein J. Org. Chem. 2023, 19, 700–718, doi:10.3762/bjoc.19.51

• . Knell et al. [40][41] reported a comparison of several catalysts, which included potassium-promoted iron, cobalt and manganese oxide catalysts, for the synthesis of 1a. Industrially, 1a is produced by the vapour phase dehydration of 2a over an iron/potassium/chromium catalyst system (Scheme 4) [42]. 2

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• activation of aryl pyrazoles, followed by the asymmetric conjugate addition to the Michael acceptor. Then, the formed cobalt enolate participates in the intermolecular aldol reaction with an aldehyde 207. The stereochemistry of this tandem procedure is controlled by the chiral Co(III) complex C4 bearing

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• –Fe(II) complex 82. Transmetalation with an organozinc produces 78a which can be trapped by an electrophile to generate the final product 79a. Cobalt-catalyzed reactions In 2014, the Yoshikai lab investigated the Co-catalyzed addition of arylzinc reagents 83 of norbornene derivatives 15 (Scheme 14

Transition-metal-catalyzed C–H bond activation as a sustainable strategy for the synthesis of fluorinated molecules: an overview

• Louis Monsigny,
• Floriane Doche and
• Tatiana Besset

Beilstein J. Org. Chem. 2023, 19, 448–473, doi:10.3762/bjoc.19.35

• functionalization of other heteroaromatic derivatives (24j, 87% yield). It should be noted that the presence of zinc triflate, a Lewis acid, was used for the activation of the electrophilic source VI. Cobalt catalysis: In 2017, Wang described the Cp*Co(III)-catalyzed trifluoromethylthiolation of 2-phenylpyridine

• of adduct J. The product 26 is released via a reductive elimination step, generating at the same time the reduced cobalt Cp*Co(I), which is converted to the active catalyst after oxidation. The same year, Yoshino and Matsunaga described a similar methodology, using the cobalt(III) complex [Cp*Co

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• 85 and porphyrin-psoralen conjugate 87 could be potential candidates for PDT applications. Recently, Charisiadis et al. [45] explored this modular click chemistry protocol for the synthesis of a noble metal-free meso-triazole cobalt porphyrin diimine-dioxime conjugate 91 by covalently connecting a

• zinc porphyrin sensitizer with a H2-evolving cobalt diimine dioxime catalyst. First, the Zn porphyrin 88b was coupled with the copper diiminedioxime complex 89 via the CuAAC click reaction to give porphyrin complex 90 in 74% yield (Scheme 18). Furthermore, a stable Co(III) complex was obtained by the

• ) CuSO4∙5H2O, sodium ascorbate, DMF/H2O (1:1), 80 °C, 32–168 h (iii) CHCl3, aq HCl (25%), 1 h (iv) MeI (120 equiv), DMF, rt, 36–72 h. Synthesis of meso-triazole-cobalt-porphyrin diimine-dioxime conjugate 91. Reactions conditions: (i) KOH, THF/MeOH/H2O, (ii) CuSO4·5H2O, sodium ascorbate, CH2Cl2/H2O/MeOH

Friedel–Crafts acylation of benzene derivatives in tunable aryl alkyl ionic liquids (TAAILs)

• Swantje Lerch,
• Stefan Fritsch and
• Thomas Strassner

Beilstein J. Org. Chem. 2023, 19, 212–216, doi:10.3762/bjoc.19.20

• nor the hexahydrate were able to catalyze the reaction in TAAILs. The hydrates of several rare-earth metal chlorides (CeCl3, NdCl3 and SmCl3) were used as well, but only small amounts of product (less than 5%) were observed, whereas the hydrates of cobalt and iron chloride were able to catalyze the

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• rearrangement was realized in an impressive yield of 95% to obtain 112 on a gram-scale, when cobalt complex C6 was used in the presence of PhSiH3 and TBHP in isopropanol. Further modifications of 112 led to the common scaffold 113 in 47% yield, which could be readily transformed to several crinipellin natural

Inline purification in continuous flow synthesis – opportunities and challenges

• Jorge García-Lacuna and
• Marcus Baumann

Beilstein J. Org. Chem. 2022, 18, 1720–1740, doi:10.3762/bjoc.18.182

• continuous flow synthesis focus on palladium [85], cobalt [86], or copper (particularly useful for the widely used CuAAc) [87]. Nevertheless, the use of metal scavengers in large scale applications is limited as often discussed [88]. The use of a homogeneous scavenger as part of batch-based offline

Mechanochemical synthesis of unsymmetrical salens for the preparation of Co–salen complexes and their evaluation as catalysts for the synthesis of α-aryloxy alcohols via asymmetric phenolic kinetic resolution of terminal epoxides

• Shengli Zuo,
• Shuxiang Zheng,
• Jianjun Liu and
• Ang Zuo

Beilstein J. Org. Chem. 2022, 18, 1416–1423, doi:10.3762/bjoc.18.147

• the unsymmetrical salens with zinc, copper, and cobalt was studied and the chiral Co–salen complex 2f was obtained in 98% yield. Hydrolytic kinetic resolution (HKR) of epichlorohydrin with water catalyzed by complex 2f (0.5 mol %) was explored and resulted in 98% ee, suggesting complex 2f could serve

• hours under nitrogen gas. Products were afforded by filtration and washed with cold methanol (20 mL × 2); Reaction conditions b: ligand 1 (1 mmol), cobalt(II) acetate tetrahydrate (1.2 mmol), and MeOH (10 mL) were gradually added to a round-bottomed flask, and stirred at 0 °C for 40 min under nitrogen

Synthesis of odorants in flow and their applications in perfumery

• Merlin Kleoff,
• Paul Kiler and
• Philipp Heretsch

Beilstein J. Org. Chem. 2022, 18, 754–768, doi:10.3762/bjoc.18.76

• oxidant (Scheme 8B) [39]. The process is performed at 120 °C at 10 bar with a residence time of 6 min, and catalyzed homogenously utilizing the established “MC-system” (manganese/cobalt/bromide) in a heated tube reactor. Remarkably, acetophenone is obtained in a good yield of 66% and in 96% purity without

Inductive heating and flow chemistry – a perfect synergy of emerging enabling technologies

• Conrad Kuhwald,
• Sibel Türkhan and
• Andreas Kirschning

Beilstein J. Org. Chem. 2022, 18, 688–706, doi:10.3762/bjoc.18.70

• ferromagnetic or ferrimagnetic nanoparticles into these materials. For this purpose, superparamagnetic iron oxide nanoparticles (SPION) are most commonly used, of which the main forms are magnetite (Fe3O4) and its oxidized form maghemite (γ-Fe2O3). Although cobalt and nickel are also highly magnetic materials

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis

• Prodip Howlader and
• Michael Schmittel

Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62

• . Transition-metal catalysts play an important role for the development of intricate pharmaceutical drugs. Although transition-metal catalysts based on rhodium, cobalt, and palladium have been intensively studied, gold catalysis has received encouraging attention only recently [67][68]. Since selectivity of

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• developed based on other oxidizing agents, such as cobalt(III) fluoride [85], phenyliodine(III) bis(trifluoroacetate) (PIFA) [86] and tert-butyl hydroperoxide [87] (Table 3). In 1999, Tomatsu and co-workers performed the synthesis of menadione (10) through demethylation of 2-methyl-1,4-dimethoxynaphthalene

• (19), using cobalt(III) fluoride as oxidizing agent (Table 3, entry 1) [85]. The obtained results showed that the cobalt(III) fluoride catalyst was comparable with other oxidizing agents already well-established for this synthesis, like silver(II) oxide and ammonium cerium(IV) nitrate. Cobalt(III

Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions

• Surendran Amrutha,
• Sankaran Radhika and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 262–285, doi:10.3762/bjoc.18.31

• , Kottayam, Kerala, 686560, India 10.3762/bjoc.18.31 Abstract Iron- and cobalt-catalyzed Sonogashira coupling reactions are becoming central areas of research in organic synthesis. Owing to their significant importance in the formation of carbon–carbon bonds, numerous green and nanoparticle protocols have

• emphasis given to green strategies. This is the first review on iron- and cobalt-catalyzed Sonogashira coupling reactions which comprehends literature up to 2020. Keywords: C–C bond formation; cobalt; green reaction; iron; nanoparticles; Sonogashira; Introduction The palladium-catalyzed cross-coupling

• exceptional versatility [13][14][15]. Therefore, the low cost first series transition metals such as iron and cobalt show higher significance than other transition metals. Naturally, Sonogashira cross-coupling reactions using cobalt or iron catalysts were reported as more cost-effective alternatives to the