Amamistatins isolated from Nocardia altamirensis

• Till Steinmetz,
• Wolf Hiller and
• Markus Nett

Beilstein J. Org. Chem. 2022, 18, 360–367, doi:10.3762/bjoc.18.40

• iron-chelating properties of the retrieved metabolites were evaluated in a chrome azurol S assay. Keywords: actinomycete; amamistatin; Nocardia; siderophore; structure elucidation; Introduction Iron is known to easily interconvert between a reduced ferrous (Fe2+) and an oxidized ferric state (Fe3

• +). This feature makes iron very useful as an enzyme cofactor for the shuffling of electrons. As a consequence of this, the transition metal is involved in many fundamental biological processes, such as respiration, photosynthesis, or nitrogen fixation [1]. In order to achieve iron homeostasis, organisms

• must be able to control the uptake of this important nutrient from the environment. In bacteria and fungi this is usually accomplished with the help of siderophores [2]. Siderophores are small molecules which, upon secretion, solubilize and coordinate ferric iron with high affinity. The ability to bind

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

• importance of this coupling reaction [7]. Later, Sonogashira-type reactions requiring only copper as catalyst alone [8] and with other transition metals [9][10][11][12] have been reported. Especially iron has attracted a great deal of attention owing to its low price, easy availability, abundant nature, and

Ready access to 7,8-dihydroindolo[2,3-d][1]benzazepine-6(5H)-one scaffold and analogues via early-stage Fischer ring-closure reaction

• Irina Kuznetcova,
• Felix Bacher,
• Daniel Vegh,
• Hsiang-Yu Chuang and
• Vladimir B. Arion

Beilstein J. Org. Chem. 2022, 18, 143–151, doi:10.3762/bjoc.18.15

• the nitro group but also to cyclization and the reductive elimination of bromine to afford 3a. The synthesis of 3b could be realized in 58% yield by using iron powder under acidic conditions. Reaction of methyl 5-(2-nitrophenyl)-4-oxopentanoate [44] and 1-benzyl-1-phenylhydrazine [36] hydrochloride in

Tenacibactins K–M, cytotoxic siderophores from a coral-associated gliding bacterium of the genus Tenacibaculum

• Yasuhiro Igarashi,
• Yiwei Ge,
• Tao Zhou,
• Amit Raj Sharma,
• Enjuro Harunari,
• Naoya Oku and
• Agus Trianto

Beilstein J. Org. Chem. 2022, 18, 110–119, doi:10.3762/bjoc.18.12

• submicromolar to micromolar ranges. Their iron-chelating activity was comparable to deferoxamine mesylate. Keywords: desferrioxamine; marine obligate bacterium; MS/MS analysis; tenacibactin; Tenacibaculum; Introduction Marine organisms continue to be a prolific resource of new bioactive natural products that

• three compounds, 3 was the most potent, inhibiting both of the cell lines at GI50 0.60 and 0.38 μM, respectively. The iron-chelating activity of compounds 1–3, determined by the chrome azurol S (CAS) assay [36], was IC50 18, 49, and 37 μM, comparable to that of deferoxamine mesylate (IC50 40 μM

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

• nickel-catalyzed C–H functionalization [10]. Iron complexes are typically cost-effective and nontoxic, and therefore, their use in domino processes represents an outstanding prospect for sustainable organic syntheses [11]. Directed C–H activations have been developed as increasingly amenable tools for

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• catalysts is desirable from both an ecological and economic standpoint. Certainly, in the past couple decades, iron has become a key player in the development of sustainable coupling chemistry and has become an indispensable tool in organic synthesis. Over the last ten years, organic chemistry has witnessed

• substantial improvements in efficient synthesis because of domino reactions. These protocols are more atom-economic, produce less waste, and demand less time compared to a classical stepwise reaction. Although iron-catalyzed domino reactions require a mindset that differs from the more routine noble-metal

• , homogenous iron catalysis they bear the chance to enable coupling reactions that rival that of noble-metal-catalysis. This review provides an overview of iron-catalyzed domino coupling reactions of π-systems. The classifications and reactivity paradigms examined should assist readers and provide guidance for

Isolation and characterization of new phenolic siderophores with antimicrobial properties from Pseudomonas sp. UIAU-6B

• Emmanuel T. Oluwabusola,
• Olusoji O. Adebisi,
• Fernando Reyes,
• Kojo S. Acquah,
• Mercedes De La Cruz,
• Larry L. Mweetwa,
• Joy E. Rajakulendran,
• Digby F. Warner,
• Deng Hai,
• Rainer Ebel and
• Marcel Jaspars

Beilstein J. Org. Chem. 2021, 17, 2390–2398, doi:10.3762/bjoc.17.156

• pseudomonine [28] are produced under iron deficiency by various Pseudomonas species to acquire iron which is essential for cell metabolism and growth [29][30]. Studies show that siderophore–antibiotic complexes may be used as a Trojan horse strategy in which the antibiotics utilize the iron-siderophore

A visible-light-induced, metal-free bis-arylation of 2,5-dichlorobenzoquinone

• Pieterjan Winant and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 2315–2320, doi:10.3762/bjoc.17.149

• splitting of boronic acids in a useful radical CH mono-arylation of benzoquinones [16]. Later research demonstrated that the metal catalyst can be replaced by a less expensive iron catalyst [17][18] or even be omitted at higher temperatures [19]. Despite their reputation as unstable intermediates

Transition-metal-free intramolecular Friedel–Crafts reaction by alkene activation: A method for the synthesis of some novel xanthene derivatives

• Tülay Yıldız,
• İrem Baştaş and
• Hatice Başpınar Küçük

Beilstein J. Org. Chem. 2021, 17, 2203–2208, doi:10.3762/bjoc.17.142

• gold(III) [43], iridium(III) [44][45], iron(III) [46], or bismuth(III) [47][48] were used as catalysts for the intermolecular hydroarylation of unactivated alkenes. Organic Brønsted acids were also used as catalysts in a smaller number of studies [49][50]. In this work, we searched for some organic

• , iron(III) chloride hexahydrate, trifluoroacetic acid (TFA), N-trifylphosphoramide (NTPA), benzoic acid, diphenyl phosphate (DPP), malonic acid, chloroacetic acid, copper(II) triflate, acetic acid, and p-toluenesulfonic acid (p-TSA) were used as catalysts. TFA gave the best yield of these catalysts with

Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• oxidative conditions, catalyzed by CuTC to give the desired product 101 (Scheme 15a). On the other hand, Yang synthesized bis(indol-3-yl)sulfides 105 through the reaction of indole with elemental sulfur, catalyzed by iron(II) sulfate in the presence of stoichiometric amounts of KI in air [83]. The I− from

• KI formed ferrous iodide, which reacts with indole to form the iron bis-indolide 107, followed by reaction with N,N-dimethylmethanethioamide to get the S atom inserted (108). A reductive elimination then generated the bis(indol-3-yl)sulfides 105 along with Fe0, which was re-oxidized by aerial oxygen

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

• could help expanding the currently available methods in organic synthesis. Manganese-catalyzed C–H activation Manganese is the twelfth most abundant element in the Earth’s crust and the third most abundant transition metal after iron and titanium [126]. The valence electron configuration of elemental

• increase the chance of finding plausible new drugs, with potent activities. Iron-catalyzed C–H activation By mass, iron is the most abundant metal on Earth. Therefore, it has been and still is widely used in many fields, from ancient but still applicable appliance as feedstock to construct basic steel

• tools [148], to the most recent nanotechnology field [149]. Iron presents powerful catalyst properties [150][151][152], including applications in C–H activation reactions [153][154][155]. In 2007, White and Chen reported a seminal work regarding predictably selective aliphatic C–H oxidations by using an

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

• [49]. To date, there are several examples of late-stage C–H amination methods that utilize iron and manganese as 3d transition metal catalysts [50][51][52]. However, intermolecular benzylic C–H amination has rarely been explored due to the challenges associated with selectivity and reactivity. In 2018

• 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

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

• -coordinating anion OCl− and as an activator of the gold(I) complex in these reactions. Other metals Although gold catalysis predominates in these types of reactions, inexpensive iron salts have also been employed successfully in hydroalkylation reactions. In 2007, Beller and co-workers reported the

• hydroalkylation of styrenes 9 using FeCl3·H2O as a source of iron(III) (Scheme 13) [46]. This reaction required higher temperatures than those used in the gold(III) methodology reported previously by Li [38] and a considerable excess (10 equiv) of alkenes (Scheme 6) to achieve the products in practice yields

Recent advances in the application of isoindigo derivatives in materials chemistry

• Andrei V. Bogdanov and
• Vladimir F. Mironov

Beilstein J. Org. Chem. 2021, 17, 1533–1564, doi:10.3762/bjoc.17.111

• also found that a device based on compound 45 (R = 2-decyltetradecyl) with the addition of iron phthalocyanine showed slightly better mobility. Liu et al. explain this effect by an improvement in the hole-type conductivity and a tight and even packing of the composite in a thin film [80]. At the same

Substituted nitrogen-bridged diazocines

• Pascal Lentes,
• Jeremy Rudtke,
• Thomas Griebenow and
• Rainer Herges

Beilstein J. Org. Chem. 2021, 17, 1503–1508, doi:10.3762/bjoc.17.107

• compounds with iron(III) to perform an intramolecular Baeyer–Mills reaction [15][21]. We found that a complete reduction of the nitro group to aniline 7 and oxidation with mCPBA is increasing the yield of the intramolecular cyclization from 39% to 62% (over two steps) for the unsubstituted diazocine 8c as

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

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• trans-THP. Feng and co-workers’ FeCl3-catalyzed Prins cyclization strategy to 4-hydroxy-substituted THP. Selectivity profile of the Prins cyclization under participation of an iron ligand. Sequential reactions involving Prins cyclization. Banerjee and co-workers’ strategy of Prins cyclization from

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

Synthesis and physicochemical evaluation of fluorinated lipopeptide precursors of ligands for microbubble targeting

• Masayori Hagimori,
• Estefanía E. Mendoza-Ortega and
• Marie Pierre Krafft

Beilstein J. Org. Chem. 2021, 17, 511–518, doi:10.3762/bjoc.17.45

• , including dendronized iron oxide nanoparticles [38] and nanodiamonds [39]) efficiently reinforce the interfacial film cohesion, thus enhancing the stability of the MBs. Various types of perfluoroalkylated amphiphiles have been reported that were designed for biomedical applications and display highly

A heterobimetallic tetrahedron from a linear platinum(II)-bis(acetylide) metalloligand

• Matthias Hardy,
• Marianne Engeser and
• Arne Lützen

Beilstein J. Org. Chem. 2020, 16, 2701–2708, doi:10.3762/bjoc.16.220

• (acetylide)platinum(II) complex [Pt(L1)2(PBu3)2] as a linear metalloligand. The reaction of this metalloligand with iron(II) cations and pyridine-2-carbaldehyde according to the subcomponent self-assembly approach yielded decanuclear heterobimetallic tetrahedron [Fe4Pt6(L2)12](OTf)8. Thus, combination of

• trans-[Pt(PBu3)2Cl2] (2). The aniline moieties in 3 were further transformed into chelating pyridylimine binding sites in the following subcomponent self-assembly process when six equivalents of metalloligand 3 were reacted with twelve equivalents of pyridine-2-carbaldehyde and four equivalents of iron

• , showing a series of signals with different charge states that could be assigned to 4. The mass spectrum also shows that the cage easily fragments upon ESI, as additional signals a–d were detected. The successful formation of iron(II)-containing metallosupramolecular tetrahedron 4 could also be proven by

Synthesis of 4-substituted azopyridine-functionalized Ni(II)-porphyrins as molecular spin switches

• Jannis Ludwig,
• Tobias Moje,
• Fynn Röhricht and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2589–2597, doi:10.3762/bjoc.16.210

• ][23][24][25][26]. Hence, 3-iodonitrobenzene (4) was reduced to obtain hydroxylamine 5, which was oxidized by iron(III) chloride to yield a mixture of 6 and starting material 4 (Scheme 1), which was directly used as a crude product in the subsequent alkaline Baeyer–Mills reaction. It is known that the

Dawn of a new era in industrial photochemistry: the scale-up of micro- and mesostructured photoreactors

• Emine Kayahan,
• Mathias Jacobs,
• Leen Braeken,
• Leen C.J. Thomassen,
• Simon Kuhn,
• Tom van Gerven and
• M. Enis Leblebici

Beilstein J. Org. Chem. 2020, 16, 2484–2504, doi:10.3762/bjoc.16.202

• increased the apparent reaction rate by a 4-fold compared to an iron packing material [68]. Therefore, a translucent material should be preferred in photoreactors. The photon flux received by the absorbing species needs to be determined accurately in order to characterize photochemical reactors. The

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• reaction as the critical step [54]. Towards this goal, they started with the hexabromination of sumanene using bromine and iron powder in nitrobenzene to provide the desired compound 94 in 61% yield. Having the bromosumanene 94 in hand, it was then subjected to the Suzuki coupling with several arylboronic

• [CpRu(η6-sumanene)]PF6 126 along with its bowl-to-bowl inversion and anticipated it to be more flexible in comparison to the iron analogue 123a, may be due to the longer C–Ru bond (Scheme 32) [64]. The complex 126 was prepared in a similar manner as its iron analogue was prepared. Quite recently

• the hexabromination using Br2 and iron powder in PhNO2. The brominated derivative 157 was then converted to the hexathiolated trithiasumanenes 158a–c by substitution reaction (Scheme 41). The structures of these functionalized heterosumanenes were confirmed by spectroscopy as well as crystallography