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

• active Cu(I) catalyst. The reaction was broadly successful with the steric and electronic nature of the aryl iodide having little effect on the reaction. Iron-catalyzed reactions Being the most earth-abundant d-block element, as well as orders of magnitude less expensive than other transition-metal

• catalysts, iron is bringing a renaissance to the idea of sustainable, green catalysis. In 2011, Ito et al. reported a diastereoselective Fe-catalyzed carbozincation of heterobicyclic alkenes 1 with diphenylzinc (74a) (Scheme 13) [47]. Using an ortho-phenylene diphosphine ligand L3, the authors were able to

Group 13 exchange and transborylation in catalysis

• Dominic R. Willcox and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2023, 19, 325–348, doi:10.3762/bjoc.19.28

• , acetals, aminals, and alkyl ethers (Scheme 26) [119][120][121]. The proposed mechanism was analogous to the GaI catalysis by Schneider, with an In‒O/B‒C exchange proposed to drive catalytic turnover. Nakazawa reported an iron–indium cooperative catalytic system for the hydroboration of nitriles with HBpin

• and HBcat (Scheme 27) [122]. The precatalyst ([Fe(CH3CN)6][cis-Fe(CO)4(InCl3)2]) was activated in situ with HBpin to give ClBpin and HInCl2 107 by In‒Cl/B‒H exchange. The indium hydride 107 underwent hydroelementation of an iron-coordinated nitrile 108, to give an indylimine iron complex 109, which

• after In‒N/B‒H exchange with HBpin gave a borylimine iron complex 110. A second hydroelementation and In‒N/B‒H exchange gave the bisborylamine 113 and regenerated the HInCl2 107 co-catalyst (Scheme 27). Conclusion Increasing concerns over the sustainability and toxicity of many transition-metal

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• exo Diels–Alder cycloaddition, which resulted in compound 159. The enol ether was oxidized by ceric ammonium nitrate (CAN) to deliver intermediate 160, which was further subjected to an iron-catalyzed hydrogen atom transfer generating tricyclic intermediate 161. Further functionalization permitted the

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

• Swantje Lerch Stefan Fritsch Thomas Strassner Professur für Physikalische Organische Chemie, Technische Universität Dresden, 01062 Dresden, Germany 10.3762/bjoc.19.20 Abstract An iron(III) chloride hexahydrate-catalyzed Friedel–Crafts acylation of benzene derivatives in tunable aryl alkyl ionic

• acylation; homogeneous catalysis; ionic liquids; iron catalysis; TAAILs; Introduction The Friedel–Crafts acylation is one of the oldest metal-catalyzed reactions in organic chemistry [1] and allows for the synthesis of a broad range of diverse compounds [2][3][4][5]. Starting from electron-rich aromatic

• 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

Germacrene B – a central intermediate in sesquiterpene biosynthesis

• Houchao Xu and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2023, 19, 186–203, doi:10.3762/bjoc.19.18

• (+)-α-vetivone (43) (Scheme 12C) [96][97] and isovalencenic acid (45) (Scheme 12D) [98] were correlated to this hydrocarbon. Recently, an iron catalyst has been developed that was applied in the isomerisation of valencene (48) to 39 (Scheme 12E) [99]. The biogenesis of 40 would be possible from I2a

Total synthesis of insect sex pheromones: recent improvements based on iron-mediated cross-coupling chemistry

• Eric Gayon,
• Guillaume Lefèvre,
• Olivier Guerret,
• Adrien Tintar and
• Pablo Chourreu

Beilstein J. Org. Chem. 2023, 19, 158–166, doi:10.3762/bjoc.19.15

• insect sex pheromones as an alternative to conventional pesticides is in constant growth. In this report, we discuss the recent contributions brought by our groups in the field of iron-catalyzed cross-couplings applied to the synthesis of insect pheromones. The pivotal question of the development of

• sustainable synthetic procedures involving cheap, non-toxic and efficient additives is also discussed, as well as the mechanistic features guiding the reactivity of such catalytic systems. Keywords: catalysis; cross-coupling; insect pheromones; iron; Introduction Public health issues related to

• carbon–carbon iron-catalyzed cross coupling as a key step were developed, capitalizing on the low toxicity and the cheap cost of this abundant metal [10]. For instance, in 1971, Kochi developed an iron-catalyzed alkyl–alkenyl cross-coupling reaction between aliphatic Grignard reagents and vinyl bromides

Improving the accuracy of ³¹P NMR chemical shift calculations by use of scaling methods

• William H. Hersh and
• Tsz-Yeung Chan

Beilstein J. Org. Chem. 2023, 19, 36–56, doi:10.3762/bjoc.19.4

• this point, as well as for the commonly recommended methods for 1H and 13C calculations [15]. However, the first method to be tried for this group of three compounds utilized the alternative CSGT NMR method recommended by Iron [7] with the TPSSTPSS [92][99][100] functional for the NMR calculation

• with the TPSSTPSS functional followed by the TPSSTPSS/CSGT NMR (Table 4, entry 7) failed, especially for compound 32. Iron further found that long-range corrected (LC) functionals all out-performed the non-corrected functionals, so this was tested as seen by entries 8 and 9 (Table 4) for both the GIAO

Microelectrode arrays, electrosynthesis, and the optimization of signaling on an inert, stable surface

• Kendra Drayton-White,
• Siyue Liu,
• Yu-Chia Chang,
• Sakashi Uppal and
• Kevin D. Moeller

Beilstein J. Org. Chem. 2022, 18, 1488–1498, doi:10.3762/bjoc.18.156

• used for the subsequent signaling experiment [20]. The hydroquinone/quinone redox couple has superior stability to the iron-based systems used previously [20], and its use leads to more reproducible binding curves. To generate the binding curve shown in Figure 4, the concentration of the integrin

• for the placement reaction. The "binding curves" generated at the electrodes with these two placement times were compared with the background signal derived from the unfunctionalized polymer. The more stable (relative to iron-based mediator pairs) hydroquinone/quinone redox pair was used, again in

1,4,6,10-Tetraazaadamantanes (TAADs) with N-amino groups: synthesis and formation of boron chelates and host–guest complexes

• Artem N. Semakin,
• Ivan S. Golovanov,
• Yulia V. Nelyubina and
• Alexey Yu. Sukhorukov

Beilstein J. Org. Chem. 2022, 18, 1424–1434, doi:10.3762/bjoc.18.148

• dynamic covalent libraries [25]. TAAD can be covalently bound to a polymer matrix through the nucleophilic nitrogen N(1) that was used to prepare scavengers of boronic acids [25]. Also, TAAD was demonstrated to serve as a scorpionate-type ligand for manganese and iron leading to complexes with the metal

Synthesis and electrochemical properties of 3,4,5-tris(chlorophenyl)-1,2-diphosphaferrocenes

• Almaz A. Zagidullin,
• Farida F. Akhmatkhanova,
• Mikhail N. Khrizanforov,
• Robert R. Fayzullin,
• Tatiana P. Gerasimova,
• Ilya A. Bezkishko and
• Vasili A. Miluykov

Beilstein J. Org. Chem. 2022, 18, 1338–1345, doi:10.3762/bjoc.18.139

• replaced with phosphacyclopentadienyl ligands. Related diphosphacyclobutadiene complexes Fe(η4-P2C2R2)2 were oxidized much more cathodically (negative by 1.7–2.0 V) [46][47], which indicated a significant contribution of the phosphacyclopentadienyl ligands to the iron atomic orbitals. Of course the

Reductive opening of a cyclopropane ring in the Ni(II) coordination environment: a route to functionalized dehydroalanine and cysteine derivatives

• Oleg A. Levitskiy,
• Olga I. Aglamazova,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2022, 18, 1166–1176, doi:10.3762/bjoc.18.121

• working electrode and an iron rod as an auxiliary electrode. The process was carried out in the potentiostatic mode at a potential of 100 mV more cathodic than the peak potential value observed in the voltammogram; a charge corresponding to 1 mol equivalent of the starting complex was passed through the

• as described above (two-compartment cell, DMF, Bu4NBF4, a glassy carbon WE, an iron wire as a CE). After 2 F/mol amount of electricity passed and subsequent protonation with PhNEt2·HCl, aryl- or benzylthiol was added. The reaction mixture was kept overnight and then the products were isolated using

Scope of tetrazolo[1,5-a]quinoxalines in CuAAC reactions for the synthesis of triazoloquinoxalines, imidazoloquinoxalines, and rhenium complexes thereof

• Laura Holzhauer,
• Chloé Liagre,
• Olaf Fuhr,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2022, 18, 1088–1099, doi:10.3762/bjoc.18.111

• ]quinoxalines 2, which was recently reported for the first time using tetraphenylporphyrin iron(III) chloride as a catalyst (Scheme 1) [11]. While the target compounds, 1,2,3-triazoloquinoxalines 3 and imidazo[1,2-a]quinoxalines 2, offer a wide range of possible applications, the current knowledge on their

• ]). Reactions of tetrazoloquinoxalines 1 to 1,2,3-triazoloquinoxalines 3 via CuAAC and denitrogenative annulation to imidazo[1,2-a]quinoxalines 2 catalyzed by an iron porphyrin catalyst 5 in combination with Zn. The scheme includes all quinoxaline-based derivatives that were obtained by these procedures so far

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

• iron (Habanolide, (12E)-oxacyclohexadec-12-en-2-one) [3][4][9][46][47]. Although, all musks of natural origin are macrocyles, most synthetic musks are polycyclic musks (PCM), while the fourth synthetic generation of musks are linear molecules [3][4]. In 1999, juniper lactone (56) was isolated from the

Structural basis for endoperoxide-forming oxygenases

• Takahiro Mori and
• Ikuro Abe

Beilstein J. Org. Chem. 2022, 18, 707–721, doi:10.3762/bjoc.18.71

• of the enzyme reaction. The released PGG2 is accepted by the peroxidase active site, and the 15-hydroperoxyl radical of PGG2 is reduced to generate PGH2. FtmOx1: Nonheme iron-dependent endoperoxygenase in the biosynthesis of verruculogen Enzyme reaction of FtmOx1 Fumitremorgin B endoperoxidase

• (FtmOx1) from Aspergillus fumigatus is the first identified nonheme iron and 2-oxoglutarate (Fe/2OG)-dependent endoperoxidase that catalyzes the formation of an endoperoxide in the biosynthesis of verruculogen [26]. Fe/2OG oxygenases utilize Fe(II) as a cofactor and 2OG and O2 as co-substrates (Scheme 3

• located on the protein surface and solvent-exposed, the distance between C21 of fumitremorgin B and the iron center is 4.6 Å and the hydroxy group of Tyr68 is near C26 of fumitremorgin B (Figure 3C). Moreover, Tyr68 is located close to C13 of fumitremorgin B, at a distance of 3.7 Å. The comparison between

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

• water can be improved by using RF heating (Scheme 6) [43]. Thus, nickel-coated iron carbide NP (FeC-Ni) was developed to drastically reduce the overpotential at 20 mA/cm2 (≈200 mV for OER). This kinetic enhancement corresponds to a temperature increase of 200 °C, although the actual temperature only

• to temperatures up to 250 °C, which was measured at the reactor outlet (Figure 4B)). The heat is generated only at the surface of the iron oxide nanoparticles (eddy currents) and this is dissipated to the surrounding environment, which is why the bulk temperature must be much lower than the surface

Direct C–H amination reactions of arenes with N-hydroxyphthalimides catalyzed by cuprous bromide

• Dongming Zhang,
• Bin Lv,
• Pan Gao,
• Xiaodong Jia and
• Yu Yuan

Beilstein J. Org. Chem. 2022, 18, 647–652, doi:10.3762/bjoc.18.65

• applied in amination reactions [17][18][19][20][21][22][23][24]. Especially, N-hydroxyphthalimide can react with arenes directly in the presence of palladium [25] or gold [26] (Scheme 1, reactions 1 and 2). Recently, we found that iron catalyzes the amination of arenes with N-hydroxyphthalimide under air

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

• metal–ligand motifs often center about iridium, ruthenium, rhodium etc. [25], the dynamic ones are constructed using copper(I), zinc(II), cadmium(II), iron(II), palladium(II), etc. as metal ions due to their more rapid ligand exchange rates [24][25][26]. The strategies to prepare inert vs dynamic

• complex [FeCu2(104)2]4+ (Figure 23), the latter controlling a double-click catalytic access to rotaxanes 109, by addition/removal of iron(II) ions [110]. Although [FeCu2(104)2]4+ is an open and flexible structure, the availability of two catalytic copper(I) centers positioned at 34 Å in the transition

• of a second equiv of copper(I) ions (Figure 30). When 0.5 equiv of iron(II) was added, the rotator arm got involved in iron(II) bis(terpyridine) complexation affording [Fe(Cu2(130))2]6+. An analogous transformation was seen for [Cu(131)]+ → [Cu2(131)]2+ → [Fe(Cu2(131))2]6+. When hydroxymethylpyridine

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

• ecofriendly method for the synthesis of 10, because it avoids mineral acid and chromium salts [52]. Sobkowiak and co-workers reported the use of iron(III) as a catalyst to activate H2O2 for the oxidation of 16 in glacial acetic acid (Table 1, entry 7) [53]. However, the oxidation process was not selective

• , and traces of 6-methyl-1,4-naphthoquinone were also identified. The reaction yields are not dependent on the type of the iron(III) salt used (perchlorate or acetate), except for iron(III) chloride, which exclusively leads to 1-chloro-2-methylnaphthalene as product [53]. Xiao and co-workers reported a

• three component catalyst system consisting of iron(III) chloride, pyridine-2,6-dicarboxylic acid (H2Pydic), and benzylamine (1:1:2.2) for the oxidation of 16 with H2O2, in tert-amyl alcohol (TAA), allowed to obtain 10 in 44% yield (Table 1, entry 9) [55]. Subsequently, Kulkarni’s group evaluated the

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