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Synthetic options for conversion of indeno[2,1‐c]fluorene‐5,8‐diones into larger polyaromatic compounds with extended π‐conjugated systems were explored. The crucial two‐fold transformation of the five‐membered ketone moieties of indeno[2,1‐c]fluorene‐5,8‐diones was based either on a one‐carbon homologation or on a ring‐expansion reaction which eventually enabled syntheses of compounds possessing substituted tribenzo[a,e,l]indeno[1,2,3‐hi]acephenanthrylenes and [5]helicenes scaffolds. The former was prepared by using a reaction sequence based on Ramirez olefination, intramolecular Heck reaction, and intermolecular Suzuki‐Miyaura cross‐coupling, whereas the latter utilized a sequence comprising Büchner−Curtius−Schlotterbeck reaction and intermolecular Suzuki‐Miyaura cross‐coupling. Scholl reaction of selected [5]helicenes yielded planarized polyaromatic compounds with the tribenzo[a,e,l]indeno[1,2,3‐hi]acephenanthrylene scaffold. Where possible, structures of products were confirmed by X‐ray diffraction analyses. Photophysical properties were determined as well. [ABSTRACT FROM AUTHOR]

Acylated N‐acetyl hexosamine hemiacetals are known for their cytotoxicity. We have previously reported that cytotoxicity can be increased by replacing one or more acyloxy groups with fluorine. Herein, we present the synthesis of 4,6‐difluorinated d‐gluco‐ and 4‐fluorinated d‐galacto‐configured hexosamine‐derived glycoconjugates with organoruthenium or ferrocene complexes and their in vitro cytotoxicity against three cancer cell lines (A2780, SK‐OV‐3, and MDA‐MB‐231) and one noncancerous cell line (HEK‐293). The attachment of the organometallic moiety at the 2‐position significantly enhanced the cytotoxicity, especially against triple‐negative MDA‐MB‐231 and the cisplatin resistant SK‐OV‐3 cancer cells. We observed a clear significance of an unprotected and acetyl protected anomeric hydroxyl for the cytotoxicity. Glycoconjugates with a non‐hydrolysable organic or organometallic group at the anomeric position were generally nontoxic. A more detailed analysis revealed that, in particular, complexes with the ruthenium tetrazene complex induced apoptosis in both SK‐OV‐3 and MDA‐MB‐231 cells, as demonstrated by western blot analysis and Annexin V‐FITC/PI staining. The structures of the two most cytotoxic organoruthenium and ferrocene glycoconjugates were confirmed by X‐ray diffraction analysis. [ABSTRACT FROM AUTHOR]

This work reports a biomimetic synthesis of polyarylated fluorene derivatives. The molecules are formed via intramolecular electrophilic aromatic substitution, resembling a cyclization leading towards the natural selaginpulvilins from selaginellins. The scope of the reaction was investigated, and the products were obtained in 60–95 % yields. Some of the compounds decompose to a stable radical. We investigated the nature and the origin of the radical using experimental methods, including EPR or electrochemical measurements, as well as theoretical methods, such as DFT calculations. Based on our observations, we hypothesize, that phenoxy radicals are formed in the first instance, which however undergo internal rearrangement to thermodynamically more stable carbon‐centered radicals. The preliminary data also show the cytotoxic properties of some of the molecules. [ABSTRACT FROM AUTHOR]

The combination of different donor moieties often results in unconventional coordination behavior. This contribution describes the synthesis of a new hybrid ligand, phosphanylferrocene amidine Ph2PfcN=CHNMe2 (1; fc=ferrocene‐1,1′‐diyl), and its coordination behavior toward the light platinum metals. Reacting compound 1 with [PdCl2(MeCN)2] produced the chelate complex [PdCl2(1‐κ2P,N)] and the bis (phosphane) complex trans‐[PdCl2(1‐κP)2], depending on the ligand‐to‐metal stoichiometry. Halide removal from [PdCl2(1‐κ2P,N)] with Na[BARF] afforded the chloride‐bridged dimer [Pd2(μ‐Cl)2(1‐κ2P,N)2][BARF]2, which was presumably in equilibrium with the mononuclear κ3‐complex [PdCl(1‐κ3Fe,P,N)][BARF] in solution (BARF=tetrakis [3,5‐bis(trifluoromethyl)phenyl]borate). The reactions of 1 with the isoelectronic precursors [(arene)MCl(μ‐Cl)]2 (M/arene=Ru(II)/p‐cymene, and Rh(III)/C5Me5) generated the respective bridge‐cleavage products [(arene)MCl2(1‐κP)], which transformed into the P,N‐chelate complexes [(arene)MCl(1‐κ2P,N)][BARF] when treated with Na[BARF] as a chloride scavenger. All this suggests preferential coordination the phosphane moiety to soft metal ions, while the coordination of the amidine moiety can be induced through changing the reaction stoichiometry or by generating a vacant coordination site at the metal ion. The compounds were characterized using a combination of standard spectroscopic methods (multinuclear NMR, IR, and ESI MS) and single‐crystal X‐ray crystallography, and compounds 1 and 3 were further studied by cyclic voltammetry. [ABSTRACT FROM AUTHOR]

This study presents the synthesis of analogues of bioactive Amaryllidaceae alkaloids that contain a five‐membered ring C and a quaternary carbon centre. The synthesis was carried out in a divergent manner, starting from a common intermediate, keto aldehyde 1 a. This intermediate was obtained by oxidative cleavage of a carbocyclic ring present in the previously synthesised tetracyclic compounds. Subsequent closure of a new heterocyclic ring B using different methods led to products with structural cores found in naturally occurring alkaloids such as pretazettine, tazettine or macronine. In addition, an analogue of egonine was prepared from the same intermediate. Our approach thus provides access to multiple structural types of potentially bioactive molecules. [ABSTRACT FROM AUTHOR]

We assembled photoresponsive mono‐ and bilayer systems with well‐defined properties from rod‐shaped molecules equipped with different photoswitches. Using properly chosen chromophores (diarylethene‐based switch and unidirectional light‐driven molecular motor), we then selectively targeted layers made of the same types of photoswitches using appropriate monochromatic light. UV‐vis analysis confirmed smooth and unrestricted photoisomerization. To achieve this, we synthesized a new class of triptycene‐based molecular pedestals adept at forming sturdy Langmuir‐Blodgett films on a water‐air interface. The films were smoothly transferred to gold and quartz surfaces. Repeated deposition afforded bilayer systems: one layer containing diarylethene‐based photoswitches and the other a unidirectional light‐driven molecular motor. Structural analysis of both mono‐ and bilayer systems revealed the molecules to be tilted with carboxylic functions pointing to the surface. At least two different polymorphs differing in monolayer thickness and tilt angle (~40° and ~60°) were identified on the gold surface. [ABSTRACT FROM AUTHOR]

Racemic carboxylic acid, a Diels‐Alder cycloadduct derived from 5‐bromo‐3‐phenyl‐α‐pyrone and acrylate dienophile, was resolved into enantiomers by diastereomeric salt crystallization. Quinidine was used as a sole resolving base. The salt of (+)‐acid crystallized from aqueous acetonitrile solution. Once this salt was separated by filtration, quinidine salt with (−)‐acid crystallized from mother liquor. As a result, both enantiomers of Diels‐Alder cycloadduct were isolated in high enantiomeric purity. [ABSTRACT FROM AUTHOR]

Large single crystals of polar tetragonal thallium antimony(III) tartrate dihydrate, Tl2[Sb2((+)C4H2O6)2]·2H2O, are grown. The crystal structure (s.g. P41), which contains the binuclear complex group [Sb2(C4H2O6)2]2− and dimer groups [Tl2O8(H2O)2], is given, together with vibrational spectra, refractive indices and their dispersion, and an analysis of SHG phase matching possibility and SHG powder measurements. The crystals allow type I phase matching for laser wavelengths ≥ 1.0103 µm. In addition, a new monoclinic (s.g. C2) antimony(III) tartrate of composition Mg[Sb3((+)C4H2O6)2((+)C4H4O6)((+)C4H5O6)]·11H2O and its crystal structure, which contains a novel type of antimony tartrate complex group [Sb3(C4H2O6)2(C4H4O6)(C4H5O6)], is presented. [ABSTRACT FROM AUTHOR]

Catalytic cyclotrimerization routes to symmetrical [9]helical indenofluorene were explored by using different transition–metal complexes and thermal conditions. Depending on the reaction conditions, the cyclotrimerizations were accompanied by dehydro‐Diels–Alder reaction giving rise to another type of aromatic compounds. Structures of both symmetrical [9]helical cyclotrimerization product as well as the dehydro‐Diels–Alder product were confirmed by single‐crystal X‐ray diffraction analyses. Limits of enantioselective cyclotrimerization were assessed as well. DFT calculations shed light on the reaction course and the origin of diminished enantioselectivity. [ABSTRACT FROM AUTHOR]

A series of molybdenum(II) compounds [(η5‐Cp')Mo(CO)2(L2)][BF4] (Cp'=C5H4(CH2)2SPh, C9H6(CH2)2OMe, L2=N,N‐chelating ligand) have been synthesized and characterized by spectroscopic and analytical methods including X‐ray crystallography. The in vitro assay on human leukemia cells MOLT‐4 has shown that the substitution in the π‐ligand in combination with suitable N,N‐chelating ligand can lead to species with cytotoxicity considerably higher than reported to cisplatin. Unusually high activity was observed for compounds bearing phenanthroline ligands [{η5‐C9H6(CH2)2OMe}Mo(CO)2(3,4,7,8‐Me4phen)][BF4] (IC50=0.7±0.3 μM) and [{η5‐C9H6(CH2)2OMe}Mo(CO)2(4,7‐Ph2phen)][BF4] (IC50 values 0.8±0.4 μM). [ABSTRACT FROM AUTHOR]

We report a Brønsted acid‐catalyzed synthesis of tetrasubstituted allenyl compounds decorated with heterocyclic sulfenyl group. The reaction proceeds readily from available propargylic alcohols in the presence of pentacarboxycyclopenatadienes (PCCPs) as organocatalysts. The developed strategy provides tetrasubstituted allene derivatives in high yields (from 55 to 98 %) and under mild reaction conditions. [ABSTRACT FROM AUTHOR]

Altering the donor properties of phosphane ligands through substituent variation is an established tool in coordination chemistry and catalysis. This contribution describes the synthesis of two new hybrid donors (L) combining 1,3,5,7‐tetramethyl‐2,4,6‐trioxa‐8‐phosphaadamantane‐8‐yl (PCg) and nitrile donor groups at different molecular scaffolds, viz. ferrocene‐1,1′‐diyl (fc) and 1,2‐phenylene. These ligands were used to prepare dimeric Au(I) complexes [Au2(μ(P,N)‐L)2][SbF6]2, which were evaluated as silver‐free, preformed catalysts in Au‐mediated cycloisomerization of (Z)‐3‐methylpent‐2‐en‐4‐yn‐1‐ol to 2,3‐dimethylfuran. The catalyst featuring the ferrocene‐based ligand, viz. [Au2(μ(P,N)‐CgPfcCN)2][SbF6]2, showed the best catalytic performance at low catalyst loading (0.5 or 0.15 mol.%), which exceeded that of its diphenylphosphanyl analog [Au2(μ(P,N)‐Ph2PfcCN)2][SbF6]2 studied earlier and the prototypical Au(I) precatalyst [Au(PPh3)(MeCN)][SbF6]. [ABSTRACT FROM AUTHOR]

Herein, we report the design and synthesis of a series of novel cationic nitrogen‐embedded polyaromatic hydrocarbons with a planar geometry. The synthetic pathway is based on catalytic C−C/C−H bond activation relay that enabled preparation of regioselectively 5,6,10,11‐tetrasubstituted naphtho[2,1,8‐ija]quinolizinium salts bearing various types of substituents. Single‐crystal X‐ray analyses of selected compounds confirmed planarity of the quinolizinium core. Most of the prepared compounds exhibited strong fluorescence (Φs up to >99 %) ranging from 420–600 nm depending on the substitution pattern. According to DFT calculations LUMO is always distributed over the quinolizinium framework regardless of the attached substituents, whereas delocalization of HOMO is related to the substitution pattern. Electrochemical measurements show irreversible reduction of all compounds, which is supported by the calculated location of LUMO orbitals. [ABSTRACT FROM AUTHOR]

We present a synthesis of novel silver complexes stabilized by bidentate ligands based on N‐heterocyclic carbenes (NHC) linked with a bisamide linker. The ligand stabilizes the silver ion in a rare chelating mode. The synthesis of the complex depends on the equimolar ratio of the silver source and the ligand precursor. In case the excess of the silver source is used, the reaction leads to the formation of an unprecedented tetranuclear silver complex, stabilized by two equivalents of the ligand, where each of the silver atoms is coordinated by one NHC and one amide moiety. The silver complexes were applied as a catalyst in a multicomponent A3 coupling and proved to be a very efficient catalyst. The reaction provided desired products in yields up to 96%, and the use of low catalytic loading, as low as 0.1 mol%, was possible without significantly compromising the effectivity of the reaction. Moreover, the complexes showed broad spectra of antimicrobial activity, with minimal inhibitory concentrations in the range of 1 to 31 μg/ml against several Gram‐positive and Gram‐negative bacteria and fungi. Presented complexes represent synthetically challenging molecules, which show great applicability in catalysis and outstanding potential as antimicrobial agents. [ABSTRACT FROM AUTHOR]

We report a modular synthetic approach towards novel derivatives of the naturally occurring arylated benzophenone selagibenzophenone A. The initial strategy for the construction of the carbon framework of the derivatives relied on the Suzuki reaction of 2,4,6‐tribromobenzonitrile, and the addition of the aryl lithium species to nitrile to generate imine. However, the formed imines showed remarkable stability toward hydrolysis. Therefore, Suzuki cross‐coupling was carried out with 2,4,6‐tribromobenzaldehyde and the subsequent addition of organometallic species to the aldehyde. Oxidation of the resulting alcohol ensured the access to desired ketones. The importance of the developed modular strategy is underlined by the discovery of several derivatives with selective cytotoxic effects and potential anti‐inflammatory activity superior to the effect of the natural product. [ABSTRACT FROM AUTHOR]

Herein we introduce fully modular synthesis leading to three representative examples of rigid molecular rods that are intended to form sturdy monolayers on various surfaces. These molecules contain two triptycene units that are designed to interlock into a compact "double‐decker" structure. Two of the three final products provided suitable crystals for X‐ray diffraction (analyzed on synchrotron), allowing deeper insight into packing in the 3‐D crystal lattice. The acidity of all three compounds were determined by capillary electrophoresis, and the pKa values ranged between 2.06‐2.53. All three rigid rods easily formed Langmuir‐Blodgett monolayers (LBMs) on the water‐air interfaces, with the area per molecule equal to 55–59 Å2/molecule, suggesting tight intermolecular packing. The thickness of all three films reached ∼19 Å after transfer to a gold (111) surface, meaning that individual molecules are tilted maximally 38° from the axis perpendicular to the surface. The structure of one of these films on a gold (111) surface was visualized by AFM. These geometrically unique molecules represent promising platforms with a wide scope of applicability in the supramolecular architecture. [ABSTRACT FROM AUTHOR]

The synthesis of enantiopure chiral boron dipyrromethenes (BODIPYs) is of importance due the intrinsic properties of BODIPYs as fluorophores that could be used as probes for molecular sensing. The present study reports an asymmetric organocatalytic cascade reaction of meso‐chloromethyl BODIPY derivatives with α,β‐unsaturated aldehydes catalyzed by a chiral secondary amine. The corresponding BODIPY‐derived cyclopropanes were produced in isolated yields 66–98%, and with diastereomeric ratios 3/2–>20/1, and 92–99% ee for major diastereomer. The synthetic utility of the protocol was exemplified on a set of additional transformations of the corresponding optically pure compounds. In addition, a study explaining the reaction mechanism (DFT computations) and photophysical characterization of all enantioenriched products were accomplished. [ABSTRACT FROM AUTHOR]

A series of inherently chiral (di)thiahelicenes/dithiophenohelicenes containing 5, 6, 9 or 11 (hetero)cycles in their helical backbone with thiophene subunit(s) embedded in it or annulated to its periphery were uniformly synthesized by intramolecular alkyne [2+2+2] cycloisomerization. Their structural, chemical and physicochemical properties such as crystal packing, oxidation, barrier to racemization, spontaneous thin film transformation or electrochemical behavior were studied and compared with the respective properties of the parent all‐carbon helicenes and dibenzohelicenes. [ABSTRACT FROM AUTHOR]

Pentasubstituted pyrrolidines are ubiquitous constituents of natural products and drugs, however the access options to them especially with respect to absolute and relative stereochemistry are not well developed. We report an asymmetric synthesis of N,2,3,4,5‐pentasubstituted pyrrolidines by oxidative single‐electron transfer‐catalyzed tandem aza‐Michael addition/radical 5‐exo cyclization/oxygenation reactions. The absolute stereochemistry is set by applying readily accessible chiral allylamines in asymmetric conjugate additions to various β‐substituted‐α,β‐unsaturated esters, which dependent on the substituent R2 sets the configuration of the two stereocenters next to the amine function, whereas two more are diastereoselectively generated by the radical 5‐exo cyclization step. This allows the diastereodivergent single‐step synthesis of pyrrolidines with four contiguous stereogenic centers. The stereoselectivity is rationalized by a predictive model. [ABSTRACT FROM AUTHOR]

Modification of amino acids is an important strategy in organic and bioorganic chemistry. In contrast to common side‐chain functionalization, backbone modification is much less explored. Especially glycine units seem to be attractive and versatile since a wide range of functionality can be potentially introduced. We report here oxidative modification of glycinates that are stable and enable further functionalization. Selective glycinate enolate oxidation by TEMPO or a FeCp2PF6/TEMPO reagent combination provides stable alkoxyamines in good to excellent yields. The methodology is expanded to glycine‐containing dipeptides demonstrating selective oxygenation at the glycine unit. The orthogonal reactivity potential of oxygenated glycines for transformation to other amino acid derivatives is explored. [ABSTRACT FROM AUTHOR]

Versatile applications and unique performance of 1,1'‐bis(diphenylphosphanyl)ferrocene (dppf) in coordination chemistry and catalysis prompted the search for its analogs. This contribution describes the synthesis of the first donor‐unsymmetric dppf congeners bearing bulky and rigid 1,3,5,7‐tetramethyl‐2,4,6‐trioxa‐8‐phosphaadamantyl (CgP) donor groups, viz. Ph2PfcPCg (1) and Ph2PfcCH2PCg (2; fc=ferrocene‐1,1'‐diyl). Bis‐phosphanes 1 and 2 were converted into air‐stable Pd(0) complexes, [Pd(ma)(L^L)] (L^L=1 and 2; ma=maleic anhydride). Together with [Pd(ma)(dppf)], these complexes were applied as catalysts in Pd‐catalyzed C−H arylation of benzoxazoles with aryl chlorides in n‐butanol as an environmentally benign solvent. Among all catalysts tested in this study, complex [Pd(ma)(2)] performed the best, providing a high‐yield and selective synthesis of 2‐arylbenzoxazoles from a range of the generally less reactive chloroarenes at low catalyst loading (typically 1 mol.%). Under similar conditions, the structurally related heterocycles (e. g. 1‐methylbenzimidazole and benzothiazole) did not react. [ABSTRACT FROM AUTHOR]

Introducing a ferrocene moiety into a molecule results in the incorporation of a metal center and a redox active moiety. This contribution describes the synthesis of FcN(CH2PPh2)2 (1; Fc=ferrocenyl), a ferrocene analog of the widely studied bis‐phosphane pincer ligands, RN(CH2PPh2)2. Compound 1 was studied as a ligand in complexes of Group 10 and 11 metal ions. The following compounds were synthesized and characterized using a combination of spectroscopic methods and single‐crystal X‐ray diffraction analysis: the square planar complexes [MX2(1‐κ2P,P')] (M/X=Ni/Cl, Pd/Cl, Pd/Br, Pd/I and Pt/Cl) and the tetrahedral complexes [M(1‐κ2P,P')2]X (M/X=Cu/PF6, Ag/SbF6 and Au/SbF6). Furthermore, a pair of open and cyclic digold(I) complexes containing bis‐phosphane 1 as a P,P‐bridging ligand, viz. [(μ(P,P')‐1)(AuCl)2] and [(μ(P,P')‐1)2Au2][SbF6]2, were isolated. Ligand 1, the corresponding phosphane selenide 1‐Se and all complexes (except for the poorly soluble [(μ(P,P')‐1)2Au2][SbF6] and unstable [Ag(1‐κ2P,P')2][SbF6]) were further analyzed by cyclic voltammetry. [ABSTRACT FROM AUTHOR]

An organocatalytic asymmetric domino Michael/α‐alkylation reaction between enals and non‐stabilized alkyl halides has been developed. Chiral secondary amine catalyzed cyclization reaction of 1‐bromo‐3‐nitropropane with α,β‐unsaturated aldehydes provides 1,2,3‐trisubstituted cyclopentane carbaldehydes with high diastereo‐ (dr up to 8 : 1) and enantioselectivities (ee up to 96 %). [ABSTRACT FROM AUTHOR]

Cooperative amino‐ and palladium catalysis utilizing heterocyclic systems containing strongly coordinating and adsorptive sulfur atom remains an underdeveloped area. Herein, we describe an enantioselective cyclization of enals with thiazole derivatives catalyzed with the combination of achiral Pd(0) complexes and chiral secondary amines. Chiral spirocyclic thiazolones were produced in yields ranging from 41% to 98% with stereoselectivities (from 5:1 to 12:1 dr, and 95–99% ee). Moreover, the developed strategy allows access to highly substituted chiral cyclopentane derivatives by additional transformations of spirocyclic thiazolones. [ABSTRACT FROM AUTHOR]

The enantioselective synthesis of chiral [7]‐helical dispirodihydro[2,1‐c]indenofluorenes (DSF‐IFs) was achieved for the first time in good yields with high er values (er up to 99 : 1). The crucial step of the whole reaction sequence was the enantioselective intramolecular [2+2+2] cycloaddition of tethered triynediols to indenofluorenediols, which was catalyzed by a Rh/SEGPHOS® complex. Further transformations led to the corresponding DSF‐IFs. The prepared helically chiral DSF‐IFs combine circularly polarized luminescence (CPL) activity (glum=∼10−3) with exceptionally high fluorescence quantum yields (up to Φlum=0.97). [ABSTRACT FROM AUTHOR]

This work reports on the preparation and structural characterization of flavo[7]helicene 1 (flavin‐[7]helicene conjugate), which was subsequently characterized at the molecular level in either an aqueous environment or an organic phase, at the supramolecular level in the form of polymeric layers, and also embedded in a lipidic mesophase environment to study the resulting properties of such a hybrid relative to its parent molecules. The flavin benzo[g]pteridin‐2,4‐dione (isoalloxazine) was selected for conjugation because of its photoactivity and reversible redox behavior. Compound 1 was prepared from 2‐nitroso[6]helicene and 6‐methylamino‐3‐methyluracil, and characterized using common structural and spectroscopic tools: circular dichroism (CD), circularly polarized luminescence (CPL) spectroscopy, cyclic voltammetry (CV), and DFT quantum calculations. In addition, a methodology that allows the loading of 1 enantiomers into an internally nanostructured lipid (1‐monoolein) matrix was developed. [ABSTRACT FROM AUTHOR]

Four complexes with bidentate N,N‐donors 2‐(furan‐2‐yl)‐5‐(pyridin‐2‐yl)‐1,3,4‐oxadiazole (fpo) and 2‐(pyridin‐2‐yl)‐5‐(thiophen‐2‐yl)‐1,3,4‐oxadiazole (pto) with general formula [M(L)2(NCS)2] (M=Co(II), L=fpo for (1); M=Co(II), L=pto for (2); M=Fe(II), L=fpo (3); M=Fe(II), L=pto (4)) are reported. Analysis and characterization of the samples was performed using standard physico‐chemical techniques – elemental analysis, nuclear magnetic resonance, Fourier transform infrared spectroscopy, single‐crystal X‐ray diffraction. Magnetic properties for 1–4 revealed large magnetic anisotropy of Co(II) complexes, and AC susceptibility measurements confirmed their single‐molecule magnetic behaviour. Furthermore, the theoretical calculations at DFT and CASSCF/NEVPT2 level of theory were exploited to better understand magnetism of these compounds. [ABSTRACT FROM AUTHOR]

AuI complexes combining hard oxygen and soft (diphenylphosphanyl)ferrocene (L) ligands in their molecules were synthesized, viz. the gold hydroxides [Au(OH)(L‐κP)] (5) and [{Au(L‐κP)}2(μ‐OH)][BF4] (4), and the oxonium cluster [{Au(L‐κP)}3(μ3‐O)][BF4] (1). In‐situ auration of 1 produced [{Au(L‐κP)}4(μ4‐O)][BF4]2 (2), which spontaneously converted into a dimeric tetragold complex featuring bridging phosphanylferrocenyl groups geminally diaurated in position 2 of the ferrocene scaffold. The same complex and its isomer incorporating ferrocene‐1,1′‐diyl bridges resulted similarly from 4. Upon crystallization, compound 5 underwent a redox reaction, producing a structurally unique, crown‐like, mixed‐valent Au0/AuI cluster, [Au7(L‐κP)6]OH. Compounds 1 and 5 were used to prepare the analogous, N‐bridged complexes, [{Au(L‐κP)}3(μ3‐NFc)][BF4] (Fc=ferrocenyl) and [{Au(L‐κP)}4(μ4‐N)][BF4]. The compounds were structurally characterized and further studied by DFT calculations. [ABSTRACT FROM AUTHOR]

(Ferrocenylmethyl)phosphane (1) oxidation with hydrogen peroxide, elemental sulfur and grey selenium produced (ferrocenylmethyl)phosphane oxide 1O, sulfide 1S and selenide 1Se, respectively, as the first isolable primary phosphane chalcogenides lacking steric protection. At elevated temperatures, compound 1O disproportionated into 1 and (ferrocenylmethyl)phosphinic acid. In reactions with [(η6‐mes)RuCl2]2, 1O underwent tautomerization into a phosphane complex [(η6‐mes)RuCl2{FcCH2PH(OH)‐κP}], whereas 1S and 1Se lost their P‐bound chalcogen atoms, giving rise to the phosphane complex [(η6‐mes)RuCl2(FcCH2PH2‐κP)] (Fc=ferrocenyl, mes=mesitylene). No tautomerization was observed in the reaction of 1O with B(C6F5)3, which instead produced a Lewis pair FcCH2P(O)H2‐B(C6F5)3. Phosphane oxide 1O added to C=O bonds of aldehydes and ketones and even to cumulenes PhNCE (E=O and S). However, both PH hydrogens were only employed in the reactions with aldehydes and cyanates. [ABSTRACT FROM AUTHOR]

Helquats (HQs) are structurally linked to helicenes and viologens, and they represent an attractive field of research in chemistry and medicinal chemistry. In the present work they were used as catalysts for the synthesis of 1,2,3,4‐tetrahydroquinolines in good yields by the Povarov reaction. The substrate scope and the capability of different helquats to promote Povarov reactions are demonstrated. Studies to elucidate mechanistic details revealed that helquats act as single‐electron transfer oxidants through a cation‐radical mechanism. The screening of the catalytic activity of HQs confirmed that an active HQ must have a LUMO energy below −8.67 eV and the standard redox potential higher (less negative) than −1.2 V vs. the ferrocene/ferrocenium redox couple. [ABSTRACT FROM AUTHOR]

A first series of fluorinated [n]helical compounds (n=5 and 6) with the dihydroindenofluorene scaffold was prepared in 5 or 9 (octafluorinated dihydroindenofluorene) steps and their photophysical properties were determined. Rh‐catalyzed intramolecular [2+2+2] cyclotrimerization of triyndiols, which were prepared in a modular fashion from simple starting material such as fluorinated haloarylcarbaldehydes, to the intermediate [n]helical dihydroindeno[2,1‐c]fluorene‐5,8‐diols was the crucial synthetic step and proceeded with high efficacy. Their further transformation gave the desired selectively fluorinated bispirodihydroindeno[2,1‐c]fluorenes. Their absorption and emission spectra were recorded. The fluorescence quantum yields were up to 92 % and the emission maxima were red‐shifted in comparison with their non‐fluorinated counterparts (386‐413 nm). [ABSTRACT FROM AUTHOR]

The present study reports an asymmetric organocatalytic cascade reaction of 4‐nitroisoxazole derivative with α,β‐unsaturated aldehydes catalysed by chiral secondary amine. Using this approach, 1,2,3‐trisubstituted cyclopropane products were obtained in isolated yields up to 98% with moderate diastereoselectivities, and enantiopurity up to 99% ee. Moreover, this synthetic protocol can be used for further applications, as shown by a set of additional transformations of the corresponding cyclopropanes and by the formal synthesis of GABA ligands. [ABSTRACT FROM AUTHOR]

A sulphonamidic moiety was utilized as an electron-withdrawing group for enhancement of anion complexation features of urea-based receptors. A series of receptors varying in acidity of sulphonamidic and urea NH groups was synthesized and thoroughly tested. The individual complexation properties reflect deprotonation/complexation equilibrium in a given molecule as a function of the substitution. The receptors containing electron-donating groups in conjugation to the sulphonamidic moiety showed higher association constants towards H2PO4 - and carboxylate anions, while those containing electron-withdrawing groups inclined to deprotonation of sulphonamidic NH. The deprotonation issue can be avoided by alkylation at the early step of receptor synthesis or it can be utilized for insertion of suitable groups that enable its anchoring on various substrates to form more elaborated receptor structures. [ABSTRACT FROM AUTHOR]

[((Diphenylphosphanyl)amino)carbonyl]ferrocene (1) has been synthesized and coordinated to light platinum metals, ruthenium, rhodium and palladium, in diverse coordination modes. Specifically, compound 1 was used to prepare the following phosphane complexes, [(η6‐mes)RuCl2(1‐κP)], [(η5‐C5Me5)RhCl2(1‐κP)], trans‐[PdCl2(1‐κP)2], and [(LNC)PdCl(1‐κP)] (mes=mesitylene, LNC=[2‐(dimethylamino‐κN)methyl]phenyl‐κC1). They were subsequently converted into cationic O,P‐chelate complexes by halide abstraction with AgClO4 and into neutral O,P‐chelate complexes by deprotonation with potassium tert‐butoxide. All coordination compounds and phosphane chalcogenides 1E (P‐bound chalcogen atom E=O, S and Se), which were also synthesised, were structurally characterised using spectroscopic methods (IR, multinuclear NMR and ESI MS) and single‐crystal X‐ray diffraction analysis. The electrochemical behaviour of the prepared compounds was studied by cyclic voltammetry, and the (LNC)Pd‐1 complexes were further studied by Mössbauer spectroscopy. [ABSTRACT FROM AUTHOR]

Merging rearrangement with radical reactions is a largely unexplored field but may hold promise for approaching scaffolds that are inaccessible by other methodology. Here a tandem nucleophilic substitution/Brook rearrangement/single‐electron transfer oxidation/radical oxygenation strategy is presented, through which α,γ‐dioxygenated ε,ζ‐unsaturated amides are efficiently prepared in a single step from enantiomerically enriched allylepoxides and 2‐silylacetamides. The resulting compounds can be easily transformed by persistent radical effect‐based 5‐exo‐trig or 6‐endo‐trig radical cyclization reactions to functionalized carbocycles bearing three or four stereocenters. The stereochemical outcome of the cyclization reactions can predicted by the Beckwith–Houk model. The cyclic compounds can be easily diversified by post‐cyclization modifications. The tandem process can be further extended by an acylation step leading to β‐dicarbonyl enolates, which were also transformed to cyclopentane and cyclohexane derivatives under oxidative conditions. [ABSTRACT FROM AUTHOR]

Tandem anionic oxy‐Cope rearrangement/radical oxygenation reactions provide δ,ϵ‐unsaturated α‐(aminoxy) carbonyl compounds, which serve as convenient precursors to diverse compound classes. Functionalized carbocycles are accessible by very rare all‐carbon 5‐endo‐trig cyclizations, but also common 5‐exo‐trig radical cyclizations, based on the persistent radical effect. The tandem reactions can be further extended by highly diastereoselective allylation or reduction steps to give complex scaffolds. [ABSTRACT FROM AUTHOR]

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A series of cationic Pt(II) complexes with chelating bis‐carbene and P,P‐ or P,S‐ligands, viz. [(C^C)Pt(X^Y)][BF4]2 (2a–e), where C^C = methylenebis(3‐methyl‐1H‐imidazol‐1‐yl‐2‐ylidene, and X^Y = Ph2PCH2CH2PPh2 (dppe) (a), Ph2P(CH2)3PPh2 (dppp) (b), 1,2‐(Ph2P)2C6H4 (dppbz) (c), [Fe(η5‐C5H4PPh2)2] (dppf) (d), and Ph2PCH2CH2SPh (e), were synthesized and structurally characterized by NMR and MS spectroscopy and by single‐crystal X‐ray diffraction analysis. Furthermore, photophysical measurements showed that these compounds were non‐emissive at room temperature. However, when cooled to 77 K, compounds 2a, 2b and 2c showed weak luminescence in the near UV region with emission maxima in the 380–395 nm range. [ABSTRACT FROM AUTHOR]

Herein is disclosed the first comprehensive study of factors that affect the regioselectivity of PdBr2(PhCN)2‐catalyzed bromoallylation of unsymmetrically substituted internal alkynes. The study was performed on a wide array of electronically and structurally diverse alkynes with aryl‐aryl, aryl‐ferrocenyl, and aryl‐alkyl substitutions. The regioselective formation of bromoallylation products was mostly driven by the polarization of the triple bond in aryl‐aryl and aryl‐ferrocenyl‐substituted ethynes. On the other hand, directing effect, which arises from the presence of a directing group in the side‐chain of aryl‐alkyl‐substituted alkynes, was the dominating factor that determined the regioselectivity of these reactions. [ABSTRACT FROM AUTHOR]

This contribution expands the still narrow class of functional ferrocene phosphanes with polar cationic groups, focusing on the synthesis and catalytic use of a series of phosphanylferrocene ligands bearing positively charged guanidinium tags, [R2PfcCH2NHC(NH2)2]Cl (3a–d), where fc = ferrocene‐1,1′‐diyl, R = isopropyl (a), cyclohexyl (b), phenyl (c), and 2‐furyl (d). To probe the influence of phosphane substituents, these compounds were studied as supporting ligands in Pd‐catalyzed Suzuki–Miyaura cross‐coupling of acyl chlorides with arylboronic acids, in analogous coupling of aryl bromides with arylboronic acids, and in Rh‐catalyzed hydroformylation of 1‐hexene using trans‐[RhCl(CO){R2PfcCH2NHC(NH2)2‐κP}2]Cl2 complexes (4a–d) as pre‐catalysts. The outcome of the cross‐coupling reactions strongly depended on the starting materials, and no ligand generated a universally applicable catalyst when combined with Pd(OAc)2. In the hydroformylation reactions, the catalyst based on 4d led to lower conversions than all others, which performed rather similarly. Overall, the phenyl‐substituted phosphane 3c emerged as a good compromise, giving rise to reasonably efficient and stable catalysts in most cases (except for Suzuki–Miyaura biaryl cross‐couplings, wherein electron‐rich alkylphosphanes performed better than 3c). [ABSTRACT FROM AUTHOR]

This work presents a general approach for synthesis of substituted [5]‐helical dispiroindeno[2,1‐c]fluorenes based on Rh‐catalyzed intramolecular cyclotrimerization of triynes. This approach was further extended for the first synthesis of configurationally stable [7]‐helical dispiroindeno[2,1‐c]fluorenes. A series of variously substituted derivatives was prepared and their photophysical and electrochemical properties were evaluated. Their fluorescence emission maxima were in the region of 351–428 nm and quantum yields up to 88 % are the highest measured among the full‐carbon helical compounds. [ABSTRACT FROM AUTHOR]

Platinum(II) complexes [Pt(C^C*)(acac)], where C^C* = 3‐R‐1‐(phenyl‐κC2)‐1H‐benzimidazol‐2‐ylidene‐κC2 (R = Me, Ph) and acac = pentane‐2,4‐dionate, reacted with functionalized acetic acids YCH2CO2H (Y = NMe2, SMe and PPh2) with elimination of acetylacetone to produce the bis‐chelate complexes of the type [Pt(C^C*)(YCH2CO2)]. Whereas the Pt(II) precursor with the less bulky methyl substituent (R) gave rise to single products having trans‐C(NHC),Y geometry, its phenyl congener reacted less selectively, affording exclusively the product with trans‐S,C(Ph) configuration for Y = SMe and mixtures of cis and trans isomers for Y = NMe2 and PPh2. These observations were well reproduced by different DFT functionals at the double‐ξ level of theory, which suggested rather small energy differences between the geometric isomers. The photophysical measurements showed that complexes [Pt(C^C*)(YCH2CO2)] are emissive in the blue region (λem 460–490 nm) with photoluminescence quantum yields up to 36 % and emission lifetimes in the range of 3–5 µs. [ABSTRACT FROM AUTHOR]

A general challenging issue in the synthesis of hemilabile ferrocene ligands is the access to highly functionalized ferrocene starting materials. These can bear donor/acceptor atoms, additional functional and structuring spectator substituents, but the preparation of such species poses general synthetic difficulties. We report herein alternative synthetic routes to hybrid ferrocene donors such as tert‐butylated phosphanylcarboxylic acids and their corresponding aldehydes. These hybrid ambiphilic species that combine Brønsted‐acidic and Lewis‐basic functional moieties in their structure were characterized by multinuclear NMR and single‐crystal X‐ray diffraction analysis. In the solid state, the mutual arrangement of functional groups at the ferrocene unit is highly dependent on hydrogen bonding interactions despite the structural hindering effect of the tert‐butyl groups introduced. The ligands were converted to gold(I) complexes and phosphane selenides to further monitor the properties and mutual influence of the functional groups in the prepared compounds. The synthesis of highly functionalized ferrocenes bearing both acidic/basic functions (PR2, R = Ph, Cy, i‐Pr, and carboxylic acids) and additional structuring substituents (bulky t‐Bu groups) is reported along with their coordination behavior and solid‐state structures. [ABSTRACT FROM AUTHOR]

A simple and efficient access to a new P‐chiral, but so far racemic ligand class featuring ortho‐trityl and ortho‐biaryl motifs is reported. The phosphines are prepared by efficient three‐ to four‐step modular syntheses from simple branched alkyl(diphenyl)phosphine oxides in 52–63% overall yield. They form stable gold complexes, which were characterized by X‐ray crystallography and spectroscopic methods. Fundamental catalytic properties of the complexes were studied in 1,6‐enyne cycloisomerization reactions of achiral substrates to benchmark their activity against the efficient achiral catalyst (JohnPhos)AuCl. The results show that the new complexes can be applied in amounts down to 100 ppm allowing the cycloisomerization reactions to be performed with turnover frequencies of 20000 h−1 and turnover numbers of up to 10000 h−1. [ABSTRACT FROM AUTHOR]

Catalysis, C-C bond cleavage, cyclotrimerization, dispiroindenofluorenes, [9]helical structure Keywords: catalysis; C-C bond cleavage; cyclotrimerization; dispiroindenofluorenes; [9]helical structure EN catalysis C-C bond cleavage cyclotrimerization dispiroindenofluorenes [9]helical structure 1 1 1 10/24/23 20231018 NES 231018 B Direction signs b show a driver which turn to take to reach the desired destination. [Extracted from the article]

anti‐β‐Amino‐α‐(aminoxy) esters or amides are synthesized by merging polar asymmetric aza‐Michael additions of lithium 1‐phenylethylamides to α,β‐unsaturated carboxylic acid derivatives and diastereoselective radical couplings with the persistent free radical TEMPO mediated or catalyzed by ferrocenium hexafluorophosphate. Aliphatic α,β‐unsaturated carboxylic derivatives gave good to excellent anti‐diastereoselectivity for the radical coupling step, whereas the selectivity remained lower for cinnamic acid derivatives. The method allows the convenient introduction of a protected oxygen functionality, which is stable to acidic, basic, hydride and hydrogenolytic reductive conditions, but can be deprotected with zinc and acetic acid in the presence of TBDMS and Boc groups without noticeable epimerization. The tandem aza‐Michael/oxygenation strategy was applied in total syntheses of the TH2 cytokine secretion modulator cytoxazone, and dipeptide fragments of the anti‐β‐amino‐α‐hydroxy acid containing macrocyclic peptides perthamide C and largamide H. With a single jumpanti‐β‐amino‐α‐hydroxy esters or amides are obtained by merging polar aza‐Michael additions of chiral 1‐phenylethylamides to α,β‐unsaturated carboxylic acid derivatives and diastereoselective radical coupling with persistent free radical TEMPO. [ABSTRACT FROM AUTHOR]

Angularly and peri‐fused tricyclic pyrrolidinopyrazolines are efficiently prepared by LiCl‐catalyzed domino aza‐Michael addition‐1,3‐dipolar cycloaddition reactions. The absolute stereochemistry is controlled in the aza‐Michael addition step, nonaflyl azide serves as effective diazo transfer reagent to the formed enolate and the resulting diazo dipole engages in the 1,3‐dipolar cycloaddition step. The resulting tricyclic pyrrolidinopyrazolines can be easily transformed to enantiomerically enriched nonproteinogenic spirocyclic α,β,γ‐triamino acids, angularly or peri‐fused tricyclic β‐prolines or pyrimidines. The activity of the tricyclic amino acid derivatives against the hepatitis C virus was determined. Angularly and peri‐fused tricyclic pyrrolidinopyrazolines are efficiently prepared by LiCl catalyzed domino aza‐Michael addition‐1,3‐dipolar cycloaddition. The resulting tricyclic pyrrolidinopyrazolines can be easily transformed to spirocyclic or condensed bicyclic α,β,γ‐triamino acid derivatives. [ABSTRACT FROM AUTHOR]

We report a facile desymmetrization of 1,4‐diethynylbicyclo[2.2.2]octane. One of the acetylene termini was protected by TMS and the desired product was purified by sublimation. It is stable but reactive, as shown by the synthesis of a complex pyridine‐terminated molecular rod containing both a bicyclo[1.1.1]pentane and a bicyclo[2.2.2]octane cage. Six crystal structures of key intermediates are presented. Facile desymmetrization of 1,4‐diethynylbicyclo[2.2.2]octane based on TMS protection of one of the acetylene termini followed by sublimation of the desired product is presented. The reactivity of this derivative was demonstrated in the synthesis of a complex pyridine‐terminated molecular rod containing both a bicyclo[1.1.1]pentane and a bicyclo[2.2.2]octane cage. [ABSTRACT FROM AUTHOR]

Abstract: The newly discovered gold‐catalysed reaction of isocyanides with hydrazoic acid generated in situ from trimethylsilyl azide and methanol (or, alternatively, from NaN3/AcOH) produces either cyanamides or 1‐substituted 1H‐tetrazol‐5‐amines, depending on the amount of available HN3. The reaction proceeds selectively and in generally high yields of either product, thus providing a particularly convenient access to a wide range of substituted 1H‐tetrazol‐5‐amines that are rather difficult to access otherwise. [ABSTRACT FROM AUTHOR]

Abstract: A new method of synthesis of an analogue of Bolm's 2,2′‐bipyridine ligand based on the catalytic [2+2+2] cyclotrimerization of 1‐halodiynes with nitriles was developed. Crucial step of the whole synthesis turned out to be homodimerization of a substituted 2‐bromopyridine to the corresponding bipyridine, that was studied and optimized. The newly prepared bipyridine (S,S)‐2 was then tested as a chiral ligand in metal‐catalyzed enantioselective reactions. Out of the studied reactions the most promising results were obtained in epoxide ring opening (82% yield, 98% ee) and Mukaiyama aldol reaction (>96% yield, 99/1 dr, 92% ee). In the case of Mukaiyama‐aldol reaction as well as in the Michael addition, novel ligand 2 proved its robustness compared to Bolm's ligand as it was less sensitive to the purity of used reagents. [ABSTRACT FROM AUTHOR]