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

• iron(II) and manganese(II) complexes with similar compositions. Interestingly, by-products incorporating the [2 + 2] macrocycles were isolated from the reaction mixtures targeting 16-Fe, 18a-Fe and 16-Mn, 18a-Mn (Figure 13) [67]. The helical geometry of [16-M]2 was attributed to the inherent

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

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

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

• , 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

• less intense maximum at 595 nm can be assigned to iron-centered transitions, which are typical for low-spin iron(II) complexes in tris(pyridylimine) binding pockets [54] (Figure 2). Also, the NMR spectroscopic analysis revealed the successful formation of discrete complexes that contain four newly

Photochromic diarylethene ligands featuring 2-(imidazol-2-yl)pyridine coordination site and their iron(II) complexes

• Andrey G. Lvov,
• Max Mörtel,
• Anton V. Yadykov,
• Frank W. Heinemann,
• Valerii Z. Shirinian and
• Marat M. Khusniyarov

Beilstein J. Org. Chem. 2019, 15, 2428–2437, doi:10.3762/bjoc.15.235

• cyclohexenone bridges show good cycloreversion quantum yields of 0.20–0.32. The thermal stability of closed-ring isomers reveals half-lives of up to 20 days in solution at room temperature. The ligands were used to explore coordination chemistry with iron(II) targeting photoswitchable spin-crossover complexes

• . Unexpectedly, dinuclear and tetranuclear iron(II) complexes were obtained, which were thoroughly characterized by X-ray crystallography, magnetic measurements, and Mössbauer spectroscopy. The formation of multinuclear complexes is facilitated by two coordination sites of the diarylethene, acting as a bridging

• ligand. The bridging nature of the diarylethene in the complexes prevents photocyclization. Keywords: diarylethene; 2-(imidazol-2-yl)pyridine; iron(II) complex; photochromism; Introduction Transition metal complexes with photoactive ligands are of great interest for advanced photonic applications [1][2

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

• yields and enantioselectivities (89–99% ee) with NFSI under basic conditions (Scheme 51). In 2016, a mild, amide-directed fluorination of benzylic, allylic, and unactivated C–H bonds was described by the Cook group [101]. By the use of the iron(II) triflate (Fe(OTf)2) as catalyst, the desired fluorides

Polysubstituted ferrocenes as tunable redox mediators

• Sven D. Waniek,
• Jan Klett,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2018, 14, 1004–1015, doi:10.3762/bjoc.14.86

• ferrocene carboxylic acids 1–4 (Scheme 2) [45][46][47][48][49][50][51][52]. The extremely bulky and electron-poor pentakis(methoxycarbonyl)cyclopentadienyl ligand gives a pseudo octahedral high-spin iron(II) complex 5, instead of forming a stable classical low-spin sandwich complex, precluding its

• ’-disubstituted ferrocene 2 can also be obtained by direct coordination of the respective substituted cyclopentadienyl ligand (CpR) to iron(II) [49]. An alternative route to the mono-, 1,1’-di- and 1,1’,3-tricarboxylic acids of ferrocene is the oxidation of the respective acetylferrocenes [47][48][53]. Ferrocene

• ferrocene carboxylic acids 1 [45][46], 2 [47][48][49], 2a [50], 2b [51][52], 3, 4 [54] and pseudo octahedral high-spin iron(II) complex 5 with pentakis(methoxycarbonyl)cyclopentadienyl ligands [55][56]. Electrochemical data of esters 1–4 and sum of Hammett substituent constants σpa and σma. 1H NMR data (δ

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

Iron complexes of tetramine ligands catalyse allylic hydroxyamination via a nitroso–ene mechanism

• David Porter,
• Belinda M.-L. Poon and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 2549–2556, doi:10.3762/bjoc.11.275

• David Porter Belinda M.-L. Poon Peter J. Rutledge School of Chemistry F11, The University of Sydney, NSW 2006, Australia 10.3762/bjoc.11.275 Abstract Iron(II) complexes of the tetradentate amines tris(2-pyridylmethyl)amine (TPA) and N,N′-bis(2-pyridylmethyl)-N,N′-dimethylethane-1,2-diamine (BPMEN

• -chlorophenyl)hydroxylamine using a molybdenum complex [32], a process that was made catalytic by adding excess N-phenylhydroxylamine [33]. The combination of iron(II) phthalocyanines [34][35] or iron(II)/iron(III) chloride [36][37][38] and N-phenylhydroxylamine effect allylic amination reactions that are

• iron(II) triflate as previously reported to generate the complexes [Fe(TPA)(CH3CN)2](OTf)2 (FeTPA, 4) [52], [Fe(BPMEN)(OTf)2] (FeBPMEN, 5) [48] and [Fe(R,R′-PDP)(OTf)2] (Fe(R,R′)-PDP, 6) [51]. Allylic amination reactions As an extension of our previously reported iron-catalysed allylic oxidation of

Oligomerization of optically active N-(4-hydroxyphenyl)mandelamide in the presence of β-cyclodextrin and the minor role of chirality

• Helmut Ritter,
• Antonia Stöhr and
• Philippe Favresse

Beilstein J. Org. Chem. 2014, 10, 2361–2366, doi:10.3762/bjoc.10.246

• .10.246 Abstract The oxidative oligomerization of a chiral mandelamide derivative (N-(4-hydroxyphenyl)mandelamide, 1) was performed in the presence of horseradish peroxidase, laccase and N,N'-bis(salicylidene)ethylenediamine-iron(II) to obtain chiral oligophenols 2. The low enantioselectivity of the

• the oligomerization of substituted electron-rich phenols in the presence of oxidizing agents [3][4]. In addition to that, N,N'-bis(salicylidene)ethylenediamine-iron(II) (iron(II)-salen) represents an alternative catalyst for oxidative coupling reactions of phenol derivatives [5]. The use of β

• from horseradish or iron(II)-salen were used as catalysts. The obtained yellow powdery oligomers 2 show high solubility in many commonly used organic solvents like acetone, THF, ethanol, methanol, acetonitrile and 1,4-dioxan. Because of the broad signals of the oligomers 2 in the 1H NMR spectra the

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• with arenediazonium salts are often more selective than traditional methods such as copper(II)-mediated Meerwein arylations [11] or protocols employing stoichiometric iron(II) or titanium(III) reductants in aqueous media [12][13][14]. This renaissance of arene diazonium chemistry has recently led to

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• iron(II) sulfate as catalyst and zinc bis(difluoromethanesulfinate) as the fluoroalkyl transfer reagent. A handful of β-difluoromethylstyrenes were obtained in moderate yields and with complete diastereoselectivity (Scheme 4) [62]. 3 Catalytic perfluoroalkylation The transition metal mediated

• [114] as well as of various arenes and heteroarenes (pyridines, pyrimidines, pyrazines, quinolines, pyrroles, thiophenes, furans, pyrazoles, imidazoles, thiazoles, oxazoles, thiadiazoles, triazoles) [115]. The yields were low to excellent, depending on the substrate (Scheme 12 and Figure 20). Iron(II

• ) sulfate and ferrocene were used alternately as catalysts in the presence or not of sulfuric acid, but other metals proved inactive. The procedures could be adapted to larger-scale synthesis (10 g). 3.3.5 Fe-catalyzed trifluoromethylation of arylboron reagents. S. L. Buchwald et al. developed an iron(II

Iron-catalyzed decarboxylative alkenylation of cycloalkanes with arylvinyl carboxylic acids via a radical process

• Jincan Zhao,
• Hong Fang,
• Jianlin Han and
• Yi Pan

Beilstein J. Org. Chem. 2013, 9, 1718–1723, doi:10.3762/bjoc.9.197

• ) in the presence of iron(II) chloride tetrahydrate (20 mol %) and 2.0 equiv of di-tert-butyl peroxide (DTBP) as the oxidant at 120 °C under nitrogen, which provided the expected (E)-(2-cyclohexylvinyl)benzene (3a), but in a moderate 54% yield (Table 1, entry 1). The use of aqueous TBHP as oxidant

Formal synthesis of (−)-agelastatin A: an iron(II)-mediated cyclization strategy

• Daisuke Shigeoka,
• Takuma Kamon and
• Takehiko Yoshimitsu

Beilstein J. Org. Chem. 2013, 9, 860–865, doi:10.3762/bjoc.9.99

• Daisuke Shigeoka Takuma Kamon Takehiko Yoshimitsu Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan 10.3762/bjoc.9.99 Abstract An iron(II)-mediated aminohalogenation of a cyclopentenyl N-tosyloxycarbamate provided new access to the key

• intermediate for the synthesis of (−)-agelastatin A (AA, 1), a potent antiproliferative alkaloid. The present synthetic endeavour offered an insight into the mechanism underlying the iron(II)-mediated aminohalogenation of N-tosyloxycarbamate, in which the radical properties of the N–iron intermediates in the

• redox states were operative. Keywords: agelastatin; aminohalogenation; iron(II); free radical; natural product synthesis; Introduction Marine organisms often produce bioactive substances that potentially serve as attractive resources for drug discovery. (−)-Agelastatin A (AA, 1), a cytotoxic alkaloid

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

• , Apartat de Correus 22085, 46071 València, Spain Institute of Condensed Matter and Nanosciences, MOST – Inorganic Chemistry, Université Catholique de Louvain, Place L. Pasteur 1, 1348 Louvain la Neuve, Belgium 10.3762/bjoc.9.39 Abstract The article deals with coordination compounds of iron(II) that may

• pressure are subjects of two separate sections. The major part of this account concentrates on selected spin crossover compounds of iron(II), with particular emphasis on the chemical and physical influences on the spin crossover behavior. The vast variety of compounds exhibiting this fascinating switching

• phenomenon encompasses mono-, oligo- and polynuclear iron(II) complexes and cages, polymeric 1D, 2D and 3D systems, nanomaterials, and polyfunctional materials that combine spin crossover with another physical or chemical property. Keywords: cages; iron(II) coordination compounds; physical techniques

Metal–ligand multiple bonds as frustrated Lewis pairs for C–H functionalization

• Matthew T. Whited

Beilstein J. Org. Chem. 2012, 8, 1554–1563, doi:10.3762/bjoc.8.177

• insertions or, in some cases, atom transfer [60]. One example with Aldridge's iron(II) aminoborylenes is presented in Scheme 9. In this case, Fe/B cooperation leads to scission of the C═O bond and oxygen-atom transfer to the borylene unit. As with cationic silylenes, the borylene complexes in Scheme 9 react

Tertiary alcohol preferred: Hydroxylation of trans-3-methyl-L-proline with proline hydroxylases

• Christian Klein and
• Wolfgang Hüttel

Beilstein J. Org. Chem. 2011, 7, 1643–1647, doi:10.3762/bjoc.7.193

• oxidation of tertiary alkyl centers is a most-straightforward but challenging approach, since these positions are sterically hindered. In contrast to P450-monooxygenases, there is little known about the potential of non-heme iron(II) oxygenases to catalyze such reactions. We have studied the hydroxylation

• demonstrates a remarkable potential of non-heme iron(II) oxygenases to oxidize substrates selectively at sterically hindered positions. Keywords: asymmetric catalysis; enzyme catalysis; hydroxyproline; α-ketoglutarate dependent iron(II) oxygenases; regioselectivity; stereoselectivity; Findings

• ability of non-heme iron(II) enzymes to oxidize tertiary carbon centers. To our knowledge, the formation of tertiary alcohols with α-ketoglutarate (α-KG) dependent iron(II) oxygenases has not been previously reported. These enzymes typically catalyze CH-activation reactions in primary and secondary

Natural product biosyntheses in cyanobacteria: A treasure trove of unique enzymes

• Jan-Christoph Kehr,
• Douglas Gatte Picchi and
• Elke Dittmann

Beilstein J. Org. Chem. 2011, 7, 1622–1635, doi:10.3762/bjoc.7.191

• halogenated by unique biochemical mechanisms through the two non-heme iron(II)-dependent halogenases BarB1 and BarB2 (Figure 6A) [40]. Further extraordinary features of the pathway include one-carbon truncation during chain elongation, E-double bond formation and thiazole ring formation. Jamaicamide The

• ) Formation of the trichloroleucyl starter unit of barbamide (7) synthesis through the non-heme iron(II)-dependent halogenases BarB1 and BarB2. B) Formation of cyclopropane and vinyl chloride functional groups in curacin A (9) and jamaicamide A (8) biosynthesis, respectively. The halogenated carbon is

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

Hybrid biofunctional nanostructures as stimuli-responsive catalytic systems

• Gernot U. Marten,
• Thorsten Gelbrich and
• Annette M. Schmidt

Beilstein J. Org. Chem. 2010, 6, 922–931, doi:10.3762/bjoc.6.98

• ) (Aldrich, 98%), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) (ABCR, 98%), N-hydroxy succinimide (NHS, Fluka), iron(III) chloride hexahydrate, iron(II) chloride tetrahydrate (Fluka, 98%), ninhydrin (Riedel-de-Haen), oligo(ethylene glycol) methylether methacrylate (OEGMA, Aldrich, Mn

• stabilization of Fe3O4 nanoparticles: The synthesis of magnetite nanoparticles on the gram scale was carried out by alkaline precipitation of iron(III) and iron(II) chloride following a method of Cabuil and Massart and is described in detail elsewhere [43]. For stabilization, the freshly synthesized

Anthracene functionalized terpyridines – synthesis and properties

• Falk Wehmeier and
• Jochen Mattay

Beilstein J. Org. Chem. 2010, 6, No. 54, doi:10.3762/bjoc.6.54

• symmetrically 4,4″-functionalized 2,2′:6′,2″-terpyridines is reported. In addition to the biscarboxylic acid 4,4″-tpy(CO2H)2 (3), the anthryl esters 4,4″-tpy(CO2CH2Anth)2 (5a) and 4,4″-tpy(CO2CH2CH2OAnth)2 (5b) were synthesized. Furthermore, both anthryl esters were used to synthesize symmetric iron(II)-bis

• (terpyridine)complexes 6a–b. Irradiation experiments were carried out with both the free ligands and an iron(II)-complex in order to investigate the photochemistry of the compounds. Keywords: anthracene; coordination chemistry; photochemistry; terpyridine; Introduction 2,2′:6′,2″-Terpyridines have been of

• diarylethenes [10][11]. There have also been reports about anthracene functionalized terpyridines in which an anthracene unit was used as a fluorescent sensor [12], spacer [13] or intercalator [14]. Herein we report the synthesis of two twofold anthracene functionalized terpyridines, their iron(II) complexes

A perfluorocyclopentene based diarylethene bearing two terpyridine moieties – synthesis, photochemical properties and influence of transition metal ions

• Falk Wehmeier and
• Jochen Mattay

Beilstein J. Org. Chem. 2010, 6, No. 53, doi:10.3762/bjoc.6.53

• ), Co(II), Ni(II) and Zn(II). The UV–vis-spectra of the iron(II) complex [Fe2+@10a], obtained by reaction of 10a with ferric chloride tetrahydrate, are shown in Figure 4. Apart from the expected bathochromic shift of the UV-bands of the ligand [18], an MLCT band at λ = 570 nm was observed. While the UV

• absorption decreases upon UV-irradiation, no significant change of the absorption in the visible region occurred. This indicates inhibition of the photochromic reaction of the diarylethene by the MLCT transition, as previously reported for other iron(II) complexes of bisterpyridine thienylethenes [10]. In

• contrast to the iron(II) complex, the ditopic ligand seems to retain its photochromic properties in the cobalt(II) and nickel(II) complexes – synthesized from CoCl2 and [Ni(acac)2], respectively – although the photocyclisation takes much longer than with free 10a (about 5 minutes compared to ca. 30 seconds