Search

The authors of this work have optimized a novel synthetic route towards glucose‐based PdII‐bis(NHC) complexes in only 4 steps with total yields up to 73 %. The synthesis route encompasses an Appel reaction towards 6‐iodo‐glucopyranosides, followed by acyl‐protection, then quaternization with imidazoles and finally the conversion of these acyl‐protected glucosyl imidazolium salts to their respective palladium(II)bis(NHC) complexes, via an intermediary silver(I) complex. Overall, 11 acyl‐protected glucosyl imidazolium iodides as NHC‐precursors and 15 complexes have been synthesized. The structure‐activity relationships of different functionalizations in these complexes and their reactivity in a model Suzuki‐Miyaura between bromobenzene and 4‐tolueneboronic acid reaction has been investigated, and a highly reactive complex leading to >99 % yield at 0.005 mol% catalytic loading has been found. [ABSTRACT FROM AUTHOR]

Four different isomeric azadibenzo[a,e]pyrenes (benzo[4,10]anthra[9,1‐gh]isoquinolines and benzo[4,10]anthra[1,9‐fg]isoquinolines) were prepared by combination of Pd‐catalyzed Sonogashira and Suzuki cross‐coupling, Brønsted acid mediated cycloisomerization and Pd‐catalysed CH‐activation reactions. The optical properties have been studied by steady‐state absorption and emission spectroscopy in different solvents and during acid titration. Trifluoroacetic acid protonation strongly affects absorption and emission properties, with variations depending on the position of the nitrogen atom of the specific compound. Electrochemical analysis showed distinct oxidation and reduction potentials. DFT calculations provided further insights into electronic properties. [ABSTRACT FROM AUTHOR]

Phosphorus‐centered disbiradicals, in which the radical sites exist as individual spin doublets with weak spin‐spin interaction have not been known so far. Starting from monoradicals of the type [⋅P(μ‐NTer)2P−R], we have now succeeded in linking two such monoradical phosphorus centers by appropriate choice of a linker. To this end, biradical [⋅P(μ‐NTer)2P⋅] (1) was treated with 1,6‐dibromohexane, affording the brominated species {Br[P(μ‐NTer)]2}2C6H12 (3). Subsequent reduction with KC8 led to the formation of the disbiradical {⋅[P(μ‐NTer)]2}2C6H12 (4) featuring a large distance between the radical phosphorus sites in the solid state and formally the highest biradical character observed in a P‐centered biradical so far, approaching 100 %. EPR spectroscopy revealed a three‐line signal in solution with a considerably larger exchange interaction than would be expected from the molecular structure of the single crystal. Quantum chemical calculations revealed a highly dynamic conformational space; thus, the two radical sites can approach each other with a much smaller distance in solution. Further reduction of 4 resulted in the formation of a potassium salt featuring the first structurally characterized P‐centered distonic radical anion (5−). Moreover, 4 could be used in small molecule activation. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Reactions of a masked N‐heterocyclic phosphinidene (mNHP, 1), a four‐membered heterocycle with a divalent P atom, with various isonitriles (tBu−NC, Dmp−NC) and carbonyls (CO, Fe(CO)5, and benzalacetone) have been studied. The isonitriles (tBu−NC and Dmp−NC) insert into a P−N bond of the four‐membered ring of 1, leading to the formation of a five‐membered heterocycle (2tBu, 2Dmp), indicating carbene‐like reactivity of the isonitriles. In exactly this way, CO, which is isolobal to isonitriles, reacts to form a five‐membered ring (3) with an exocyclic C=O double bond. If, on the other hand, Fe(CO)5 is used as a CO source, a CO molecule is inserted analogously, however, the remaining Fe(CO)4 fragment is bound via a phosphorus‐iron dative bond to the five‐membered heterocycle. When mNHP 1 reacts with the α,β‐unsaturated ketone benzalacetone, phosphinidene reactivity is observed for 1. This means that the four‐membered ring opens and the P atom reacts with the benzalacetone in a cyclization reaction to form a 1,2‐oxaphospha‐cyclopentene. Theoretical studies of the five‐membered heterocycles 2 and 3 carrying eight π electrons show that zwitterionic Lewis representations dominate in the resonance scheme and only a very low biradical character (<5 %) is found. [ABSTRACT FROM AUTHOR]

2‐(1‐Hydroxyethylidene)malononitrile (4) is commercially sold as the keto isomer and is described in the literature as either a keto (4 b) or enol (4 a) species. Using NMR techniques and single crystal X‐ray diffraction, we were able to show that 4 exists exclusively as the enol isomer (4 a) in solution as well as in the solid state, which agrees with quantum chemical calculations. By adding one or two equivalents of the Lewis acid B(C6F5)3, the mono‐ or diadducts are formed in exergonic reactions, in which the enol form is further thermodynamically stabilized. The structure and acidity of enol 4 a and its borane adducts are discussed based on experimental and theoretical results. [ABSTRACT FROM AUTHOR]

This report describes a one‐pot multi‐step procedure to obtain double azahelicenes via nucleophilic fluorine substitution of 2,2‐di(2‐bromophenyl)‐1,1‐difluoroalkenes and palladium‐catalysed ring closing reaction. The developed synthesis approach allows easy diversification of substituents at all four fragments of the obtained X‐shaped aza[4,6]helicene entity. Yields range from 20 % to 60 % among 12 product examples. X‐ray single crystal analysis reveals formation of (P,P) and (M,M) enantiomer mixture of products. Optical and electrochemical properties of selected products were studied by performing UV/Vis absorption, photoluminescence and cyclic voltammetry measurements. Experimental results are supported by (TD)‐DFT, NICS and NICS2BC calculations. [ABSTRACT FROM AUTHOR]

The incorporation of heteroatoms into polycyclic aromatic hydrocarbons (PAHs) has been recognized as valuable tool to alter their inherent optical and electrochemical properties and are thought as promising next‐generation semiconductor materials. We herein report the synthesis of diindenopyrene, a fragment of C70 and two of its nitrogen‐doped aza‐analogs. The developed synthetic procedure is based on Brønsted‐acid‐mediated cycloisomerization followed by Pd‐catalyzed C−H‐activation as key‐steps. The impact of N‐doping on the optical and electrochemical properties has been studied and the experimental results are supported by DFT calculations. [ABSTRACT FROM AUTHOR]

C10a‐Acetoxylated perhydroazepino[1,2‐a]‐indoles, accessible via visible light‐mediated sensitized photooxygenation of cyclo‐hepta[b]indoles, are precursors to structurally elaborate carbon‐centered radicals. Their photoredox‐catalyzed SET reduction by phenothiazine or phenoxazine photocatalysts, followed by fragmentation and C−O bond cleavage, liberates tricyclic α‐amino‐α‐carbonyl radicals that readily engage in radical addition reactions with silyl enol ethers and silyl ketene acetals. The C−C functionalized azepinoindole[1,2‐a]indoles are useful building blocks for the synthesis of polycyclic indole derivatives as shown by the controlled borohydride reduction of a C10a‐methylenecarboxylate derivative, which leads stereoselectively to tetracyclic azepino[1,2‐a]furo[3,2‐b]indoles. The photocatalytic method developed herein is also suitable for the radical functionalization of simple α‐acetoxy acetophenones. [ABSTRACT FROM AUTHOR]

A series of N‐doped Benzo[b]fluoranthenes was synthesized. Specifically varying the position of the Nitrogen atom in all four positions of the bottom ring. In the last reaction step the five‐membered ring of the unsubstituted core structure is formed by palladium catalyzed CH‐activation. This synthetic approach allows for the selective introduction of heteroatoms into the core structure and leads to four regioisomeric products. Subsequently the optical and electrochemical properties of these polyaromatic heterocycles were compared. DFT/TD‐DFT and NICS calculations were performed to further analyze, how the position of Nitrogen impacts the overall characteristics of the molecules. This composes a thorough study on the chemical behavior of N‐doped Benzo[b]fluoranthenes. [ABSTRACT FROM AUTHOR]

A series of thienoindolizine structural isomers have been synthesized in a one‐pot, two‐step procedure starting from easily accessible gem‐difluoroalkene functionalized bromothiophenes. The developed method gives easy access to a range of thienoindolizine products containing thieno[3,2‐g]‐, thieno[3,4‐g]‐ and thieno[2,3‐g]indolizine core structures. The described synthesis strategy consists of a base mediated, transition metal free nucleophilic substitution of fluorine atoms by nitrogen containing heterocycles followed by a Pd catalyzed intramolecular cyclization. A series of 22 final product examples has been obtained with yields ranging from 29 % to 95 %. UV/Vis absorption, fluorescence spectroscopy, fluorescence lifetime measurements and cyclic voltammetry were carried out with selected final products to evaluate structural effects on photophysical and electrochemical properties. (TD)DFT and NICS calculations were performed to provide insight into the electronic properties of the four core molecular structures. [ABSTRACT FROM AUTHOR]

Differently substituted phenyl isonitriles (with C−H bonds in ortho‐position) and naphthyl isonitriles were reacted with the cyclic biradical [⋅P(μ‐N‐Ter)2P⋅] (1). Insertion of the isonitrile formed a cyclic five‐membered biradical [⋅P(NTer)2C(R)P⋅] (2R, R=phenyl, naphthyl) in the first step, followed by C−H activation at the aryl substituent, resulting in novel azaphospholes (5R), which could be isolated and fully characterized. The formation of the azaphospholes can be prevented by the addition of a second equivalent of isonitrile, which causes the blocking of the radical centers in 2R by adduct formation (3R). Quantum mechanical calculations showed that a significant increase in the aromaticity of the benzo‐ and naphtho‐azaphospholes is one of the driving forces for the activation process leading to the formation of thermodynamically favored azaphospholes. Targeted activation of C−H bonds using biradical systems represents a new synthetic approach to generate benzo‐ and naphtho‐azaphospholes. [ABSTRACT FROM AUTHOR]

The chlorination of 1,2‐diphosphinobenzene with PCl5 to 1,2‐bis(dichlorophosphino)benzene was performed with high yields (93 %) despite the high number of P−H functions. The method was further applied to other phosphanes, enabling the first synthesis and complete characterization of 1,2,4‐tris(dichlorophosphino)benzene (89 % yield) and 1,2,4,5‐tetrakis(dichlorophosphino)benzene (91 % yield), valuable precursors for example for binuclear complexes, coordination polymers, organic wires, or metal–organic frameworks. The application of the chlorophosphanes in base induced ring closure reactions with primary amines is demonstrated. [ABSTRACT FROM AUTHOR]

A series of hitherto unknown 5,14‐diphenylbenzo[j]naphtho[2,1,8‐def][2,7]phenanthrolines, containing a 5‐azatetracene and a 2‐azapyrene subunit, were prepared by combination of Pd‐catalyzed cross‐coupling reactions with a one‐pot Povarov/cycloisomerization reaction. In the final key step four new bonds are formed in one step. The synthetic approach allows for a high degree of diversification of the heterocyclic core structure. The optical and electrochemical properties were studied experimentally and by DFT/TD‐DFT and NICS calculations. Due to the presence of the 2‐azapyrene subunit, the typical electronic nature and characteristics of the 5‐azatetracene moiety are lost and the compounds are electronically and optically more related to 2‐azapyrenes. [ABSTRACT FROM AUTHOR]

Redox‐active tungsten alkyne complex‐based phosphines of the type [Tp*W(CO)Br(η2‐C2(PR2)x] (x=1, 2; R=Ph, i‐Pr) and coordination experiments with the corresponding diphosphines are described. The pKB values of the terminal free phosphine groups were estimated indirectly by the 1JP/Se coupling constants in the associated P‐selenides. A ten orders of magnitude higher basicity for the bis(diisopropyl)phosphine derivatives compared to the diphenyl congener as well as a significant difference in basicity of the phosphine depending on its position at the alkyne was determined. The diphosphines were utilized for comparative coordination experiments with Ni(II) and Cu(I) as first row transition metals. The heterobimetallic complexes {[Tp*W(CO)Br(μ‐η2‐C,C′‐κ2‐P,P′‐C2(PR2)2]NiCl2} (R=Ph, i‐Pr) were synthesized and fully characterized, the large difference in basicity and donor strength being underlined by a different degree of stability. Furthermore, two Cu(I) complexes of the isopropyl diphosphine derivative are presented and discussed; one of both being a dinuclear phenanthroline Cu(I) complex and the other a tetranuclear complex exhibiting an angled Cu2Br+ core. [ABSTRACT FROM AUTHOR]

Electrophilic aromatic substitution (EAS) can provide a straightforward approach to the efficient synthesis of functionalized complex aromatic molecules. In general, Lewis acids serve as a beneficial stimulus for the formation of a Wheland complex, the intermediate in the classical SEAr mechanism of EAS, which is responsible for H/E (E=electrophile) substitution under formal H+ elimination. Herein, we report an unusual variant of EAS, in which a complex molecule such as the tricyanomethane, HC(CN)3, is activated with a strong Lewis acid (B(C6F5)3) to the point where it can finally be used in an EAS. However, the Lewis acid here causes the isomerization of the tricyanomethane to the ketenimine, HN=C=C(CN)2, which in turn directly attacks the aromatic species in the EAS, with simultaneous proton migration of the aromatic proton to the imino group, so that no elimination occurs that is otherwise observed in the SEAr mechanism. By this method, it is possible to build up amino‐malononitrile‐substituted aromatic compounds in one step. [ABSTRACT FROM AUTHOR]

We show that the carboxyl‐functionalized ionic liquid 1‐(carboxymethyl)pyridinium bis(trifluoromethylsulfonyl)imide [HOOC‐CH2‐py][NTf2] exhibits three types of hydrogen bonding: the expected single hydrogen bonds between cation and anion, and, surprisingly, single and double hydrogen bonds between the cations, despite the repulsive Coulomb forces between the ions of like charge. Combining X‐ray crystallography, differential scanning calorimetry, IR spectroscopy, thermodynamic methods and DFT calculations allows the analysis and characterization of all types of hydrogen bonding present in the solid, liquid and gaseous states of the ionic liquid (IL). We find doubly hydrogen bonded cationic dimers (c+=c+) in the crystalline phase. With increasing temperature, this binding motif opens in the liquid and is replaced by (c+−c+−a− species, with a remaining single cationic hydrogen bond and an additional hydrogen bond between cation and anion. We provide clear evidence that the IL evaporates as hydrogen‐bonded ion pairs (c+−a−) into the gas phase. The measured transition enthalpies allow the noncovalent interactions to be dissected and the hydrogen bond strength between ions of like charge to be determined. [ABSTRACT FROM AUTHOR]

The activation of C−Br bonds in various bromoalkanes by the biradical [⋅P(μ‐NTer)2P⋅] (1) (Ter=2,6‐bis‐(2,4,6‐trimethylphenyl)‐phenyl) is reported, yielding trans‐addition products of the type [Br−P(μ‐NTer)2P−R] (2), so‐called 1,3‐substituted cyclo‐1,3‐diphospha‐2,4‐diazanes. This addition reaction, which represents a new easy approach to asymmetrically substituted cyclo‐1,3‐diphospha‐2,4‐diazanes, was investigated mechanistically by different spectroscopic methods (NMR, EPR, IR, Raman); the results suggested a stepwise radical reaction mechanism, as evidenced by the in‐situ detection of the phosphorus‐centered monoradical [⋅P(μ‐NTer)2P‐R].< To provide further evidence for the radical mechanism, [⋅P(μ‐NTer)2P‐Et] (3Et⋅) was synthesized directly by reduction of the bromoethane addition product [Br‐P(μ‐NTer)2P‐Et] (2 a) with magnesium, resulting in the formation of the persistent phosphorus‐centered monoradical [⋅P(μ‐NTer)2P‐Et], which could be isolated and fully characterized, including single‐crystal X‐ray diffraction. Comparison of the EPR spectrum of the radical intermediate in the addition reaction with that of the synthesized new [⋅P(μ‐NTer)2P‐Et] radical clearly proves the existence of radicals over the course of the reaction of biradical [⋅P(μ‐NTer)2P⋅] (1) with bromoethane. Extensive DFT and coupled cluster calculations corroborate the experimental data for a radical mechanism in the reaction of biradical [⋅P(μ‐NTer)2P⋅] with EtBr. In the field of hetero‐cyclobutane‐1,3‐diyls, the demonstration of a stepwise radical reaction represents a new aspect and closes the gap between P‐centered biradicals and P‐centered monoradicals in terms of radical reactivity. [ABSTRACT FROM AUTHOR]

The oxidation of silylated hydrazine, (Me3Si)2N−N(H)SiMe3, with silver salts led to the formation of a highly labile hydrazinium‐yl radical cation, [(Me3Si)2N−N(H)SiMe3].+, at very low temperatures (decomposition > −40 °C). EPR, NMR, DFT and Raman studies revealed the formation of a nitrogen‐centered radical cation along the N−N unit of the hydrazine. In the presence of the weakly coordinating anion [Al{OCH(CF3)2}4]−, crystallization and structural characterization in the solid state were achieved. The hydrazinium‐yl radical cation has a significantly shortened N−N bond and a nearly planar N2Si3 framework, in contrast to the starting material. According to DFT calculations, the shortened N−N bond has a total bond order of 1.5 with a π‐bond order of 0.5. The π bond can be regarded as a three‐π‐electron, two‐center bond. [ABSTRACT FROM AUTHOR]

The oxidation of silylated hydrazine, (Me3Si)2N−N(H)SiMe3, with silver salts led to the formation of a highly labile hydrazinium‐yl radical cation, [(Me3Si)2N−N(H)SiMe3].+, at very low temperatures (decomposition > −40 °C). EPR, NMR, DFT and Raman studies revealed the formation of a nitrogen‐centered radical cation along the N−N unit of the hydrazine. In the presence of the weakly coordinating anion [Al{OCH(CF3)2}4]−, crystallization and structural characterization in the solid state were achieved. The hydrazinium‐yl radical cation has a significantly shortened N−N bond and a nearly planar N2Si3 framework, in contrast to the starting material. According to DFT calculations, the shortened N−N bond has a total bond order of 1.5 with a π‐bond order of 0.5. The π bond can be regarded as a three‐π‐electron, two‐center bond. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Alkali metal salts, M+[Ter(iPr)P−C(=S)−P(iPr)2S].− (M=Na, K; 2_M; Ter=2,6‐bis‐(2,4,6‐trimethylphenyl)phenyl) containing a room‐temperature‐stable thioketyl radical anion were obtained by reduction of the thioketone precursor, Ter(iPr)P−C(=S)−P(iPr)2S (1), with alkali metals (Na, K). Single‐crystal X‐ray studies as well as EPR spectroscopy revealed the unequivocal existence of a thioketyl radical anion in the solid state and in solution, respectively. The computed Mulliken spin density within 2_M is mainly located at the sulfur (49 %) and the carbonyl carbon (33 %) atoms. Upon adding [2.2.2]‐cryptand to the radical species 2_K to minimize the interionic interaction, an activation reaction was observed, yielding a potassium salt with a phosphanyl thioether based anion, [K(crypt)]+[Ter(iPr)P−C(−S‐iPr)−P(iPr)2S]− (3) as the product of an intermolecular shift of an iPr group from a second anion. The products were fully characterized and application of the radical anion as a reducing agent was demonstrated. [ABSTRACT FROM AUTHOR]

The article titled "Cover Picture: Rational Design of a Phosphorus-Centered Disbiradical" in the journal Angewandte Chemie International Edition features research on arranging diatoms (tiny algae) under a microscope using a single hair. The diatoms represent the formula of a disbiradical described in the article and its characteristic three-line EPR signal. The background image of the Milky Way symbolizes the interaction through space that explains the unique EPR signal. The article also includes research on photoswitch azobenzene-spiropyran dyads, lignin O-demethylation, and the design of a large polyoxometalate cluster with specific properties. [Extracted from the article]

The article titled "Titelbild: Design eines Phosphor-zentrierten Disbiradikals" in the journal Angewandte Chemie features research on arranging diatoms, small algae, under a microscope using a single hair. The diatoms represent the formula of a disbiradical described in the article and its characteristic three-line EPR signal. The background image of the Milky Way symbolizes the interaction through space that explains the unique EPR signal. The article also includes research on photoswitch azobenzene-spiropyran dyads, lignin O-demethylation, and the design of a large polyoxometalate cluster with specific properties. [Extracted from the article]

Formal coordination of phosphorus(III) by a calix[4]pyrrole Schiff base ligand was achieved through the reaction of this ligand with PCl3 under basic conditions. The reaction product adopts a Pacman conformation with two P−Cl moieties, one in exo and one in endo position. It represents the first non‐metal compound of calix[4]pyrrole Schiff base ligands and of Pacman ligands in general. The spatial neighborhood of the two phosphorus atoms enables cooperative reactions. As a first example, the chloride abstraction with AgOTf is presented, yielding a macrocyclic dication with two embedded phosphorus(III) monocations, which both undergo a cooperative, internal activation reaction with an adjacent C=N double bond. This intramolecular redox process affords two pentacoordinated phosphorus(V) centers within the Pacman dication. All reaction products were fully characterized and all results are supported by computations. [ABSTRACT FROM AUTHOR]

N‐Benzyl‐ and N‐2°‐alkylpyridinium salts were engaged in visible‐light‐driven, photoredox‐induced radical‐cationic three‐component couplings with N‐methylmaleimide and acrylonitrile as radical acceptors, in combination with 1,1‐diarylethylenes as donor alkenes. These multicomponent coupling reactions could be achieved under mild conditions, with high efficiency, and to furnish diverse 3,4‐disubstituted pyrrolidin‐2,5‐dione products with high stereoselectivity. In addition, 2,3‐diaryl‐1,3‐butadienes could be utilized as alternative donor alkene components, to furnish diastereomerically pure 1,2,3‐trisubstituted 1,3‐butadienes as the coupling products. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Me3Si−X (X=CN, N3, OCN, and SCN) was treated with the Lewis acids GaCl3 and B(C6F5)3 in toluene yielding the desired adducts Me3Si−X→GaCl3 and Me3Si−X→B(C6F5)3. All synthesized adducts were isolated and completely characterized including single crystal structure elucidations. The different structures, thermodynamics of formation and charge transfer effects are discussed on the basis of experimental and theoretical data. [ABSTRACT FROM AUTHOR]

Within the second funding period of the SPP 1708 "Material Synthesis near Room Temperature",which started in 2017, we were able to synthesize novel anionic species utilizing Ionic Liquids (ILs) both, as reaction media and reactant. ILs, bearing the decomposable and non‐innocent methyl carbonate anion [CO3Me]−, served as starting material and enabled facile access to pseudohalide salts by reaction with Me3Si−X (X=CN, N3, OCN, SCN). Starting with the synthesized Room temperature Ionic Liquid (RT‐IL) [nBu3MeN][B(OMe)3(CN)], we were able to crystallize the double salt [nBu3MeN]2[B(OMe)3(CN)](CN). Furthermore, we studied the reaction of [WCC]SCN and [WCC]CN (WCC=weakly coordinating cation) with their corresponding protic acids HX (X=SCN, CN), which resulted in formation of [H(NCS)2]− and the temperature labile solvate anions [CN(HCN)n]− (n=2, 3). In addition, the highly labile anionic HCN solvates were obtained from [PPN]X ([PPN]=μ‐nitridobis(triphenylphosphonium), X=N3, OCN, SCN and OCP) and HCN. Crystals of [PPN][X(HCN)3] (X=N3, OCN) and [PPN][SCN(HCN)2] were obtained when the crystallization was carried out at low temperatures. Interestingly, reaction of [PPN]OCP with HCN was noticed, which led to the formation of [P(CN)2]−, crystallizing as HCN disolvate [PPN][P(CN⋅HCN)2]. Furthermore, we were able to isolate the novel cyanido(halido) silicate dianions of the type [SiCl0.78(CN)5.22]2− and [SiF(CN)5]2− and the hexa‐substituted [Si(CN)6]2− by temperature controlled halide/cyanide exchange reactions. By facile neutralization reactions with the non‐innocent cation of [Et3HN]2[Si(CN)6] with MOH (M=Li, K), Li2[Si(CN)6] ⋅ 2 H2O and K2[Si(CN)6] were obtained, which form three dimensional coordination polymers. From salt metathesis processes of M2[Si(CN)6] with different imidazolium bromides, we were able to isolate new imidazolium salts and the ionic liquid [BMIm]2[Si(CN)6]. When reacting [Mes(nBu)Im]2[Si(CN)6] with an excess of the strong Lewis acid B(C6F5)3, the voluminous adduct anion {Si[CN⋅B(C6F5)3]6}2− was obtained. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Conversion of 1,2‐bis(dichlorophosphino)benzene with sterically demanding primary amines led to the formation of 1,3‐dichloro‐2‐aza‐1,3‐diphosphaindanes of the type C6H4(μ‐PCl)2N‐R. Reduction yielded the corresponding 2‐aza‐1,3‐diphosphaindane‐1,3‐diyls (1), which can be described as phosphorus‐centered singlet biradical(oid)s. Their stability depends on the size of the substituent R: While derivatives with R=Dmp (2,6‐dimethylphenyl) or Ter (2,6‐dimesitylphenyl) underwent oligomerization, the derivative with very bulky R=tBuBhp (2,6‐bis(benzhydryl)‐4‐tert‐butylphenyl) was stable with respect to oligomerization in its monomeric form. Oligomerization involved activation of the fused benzene ring by a second equivalent of the monomeric biradical and can be regarded as formal [2+2] (poly)addition reaction. Calculations indicate that the biradical character in 1 is comparable with literature‐known P‐centered biradicals. Ring‐current calculations show aromaticity within the entire ring system of 1. [ABSTRACT FROM AUTHOR]

A pair of diastereomeric dinuclear complexes, [Tp′(CO)BrW{μ‐η2‐C,C′‐κ2‐S,P‐C2(PPh2)S}Ru(η5‐C5H5)(PPh3)], in which W and Ru are bridged by a phosphinyl(thiolato)alkyne in a side‐on carbon P,S‐chelate coordination mode, were synthesized, separated and fully characterized. Even though the isomers are similar in their spectroscopic properties and redox potentials, the like‐isomer is oxidized at W while the unlike‐isomer is oxidized at Ru, which is proven by IR, NIR and EPR‐spectroscopy supported by spectro‐electrochemistry and computational methods. The second oxidation of the complexes was shown to take place at the metal left unaffected in the first redox step. Finally, the tipping point could be realized in the unlike isomer of the electronically tuned thiophenolate congener [Tp′(CO)(PhS)W{μ‐η2‐C,C′‐κ2‐S,P‐C2(PPh2)S}Ru(η5‐C5H5)‐(PPh3)], in which valence trapped WIII/RuII and WII/RuIII cationic species are at equilibrium. [ABSTRACT FROM AUTHOR]

A convenient three‐step synthesis of dibenzo[a,j]acridines is reported which relies on regioselective Pd‐catalyzed cross‐coupling reactions of 2,3,5,6‐tetrachloropyridine and subsequent Brønsted acid mediated cycloisomerization. Products are obtained in good yields and the method is broadly applicable. For selected dibenzo[a,j]acridines, photophysical and electrochemical properties were studied. [ABSTRACT FROM AUTHOR]

Alkyne complexes with vicinal substitution by a Lewis acid and a Lewis base at the coordinated alkyne are prospective frustrated Lewis pairs exhibiting a particular mutual distance and, hence, a specific activation potential. In this contribution, investigations on the generation of a WII alkyne complex bearing a phosphine as Lewis base and a carbenium group as Lewis acid are presented. Independently on potential substrates added, an intramolecular cyclisation product was always isolated. A subsequent deprotonation step led to an unprecedented side‐on λ5‐phosphinyne complex, which is interpreted as highly zwitterionic according to visible absorption spectroscopy supported by TD‐DFT. Low‐temperature 31P NMR and EPR spectroscopic measurements combined with time‐dependent IR‐spectroscopic monitoring provided insights in the mechanism of the cyclisation reaction. Decomposition of the multicomponent IR spectra by multivariate curve resolution and a kinetic hard‐modelling approach allowed the derivation of kinetic parameters. Assignment of the individual IR spectra to potential intermediates was provided by DFT calculations. [ABSTRACT FROM AUTHOR]

Tetrahydrocarbazoles and perhydrocyclohepta[b]indoles undergo a catalytic cascade singlet oxygenation in alkaline medium, which leads to chiral tricyclic perhydropyrido‐ and perhydroazepino[1,2‐a]indoles in a single operation. These photooxygenation products are new synthetic equivalents of uncommon C,N‐diacyliminium ions and can be functionalized with the aid of phosphoric acid organocatalysis. [ABSTRACT FROM AUTHOR]

Functionalized imidazolium cations were combined with the hexacyanidosilicate anion, [Si(CN)6]2–, by salt metathesis reactions with K2[Si(CN)6], yielding novel ionic compounds of the general formula [R–Ph(nBu)Im]2[Si(CN)6] {R = 2‐Me (1), 4‐Me (2), 2,4,6‐Me = Mes (3), 2‐MeO (4), 2,4‐F (5), 4‐Br (6); Im = imidazolium}. All synthesized imidazolium hexacyanidosilicates decompose upon thermal treatment above 95 °C (96 – 164 °C). Furthermore, the hexa‐borane‐adduct [Mes(nBu)Im]2{Si[(CN)B(C6F5)3]6}·6CH2Cl2 (7), which is thermally stable up to 215 °C, was obtained from the reaction of 3 with Lewis acidic B(C6F5)3. In CH3CN solution, decomposition of the hexaadduct to the Lewis‐acid‐base adduct CH3CN–B(C6F5)3 and [(C6F5)3B·(µ‐CN)·B(C6F5)3]– was observed. All synthesized compounds were isolated in good yields and were completely characterized including single crystal structure elucidations. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Although pure hydrogen cyanide can spontaneously polymerize or even explode, when initiated by small amounts of bases (e.g. CN−), the reaction of liquid HCN with [WCC]CN (WCC=weakly coordinating cation=Ph4P, Ph3PNPPh3=PNP) was investigated. Depending on the cation, it was possible to extract salts containing the formal dihydrogen tricyanide [CN(HCN)2]− and trihydrogen tetracyanide ions [CN(HCN)3]− from liquid HCN when a fast crystallization was carried out at low temperatures. X‐ray structure elucidation revealed hydrogen‐bridged linear [CN(HCN)2]− and Y‐shaped [CN(HCN)3]− molecular ions in the crystal. Both anions can be considered members of highly labile cyanide‐HCN solvates of the type [CN(HCN)n]− (n=1, 2, 3 ...) as well as formal polypseudohalide ions. [ABSTRACT FROM AUTHOR]

Attempts have been made to prepare salts with the labile tris(trimethylsilyl)chalconium ions, [(Me3Si)3E]+ (E=O, S), by reacting [Me3Si‐H‐SiMe3][B(C6F5)4] and Me3Si[CB] (CB−=carborate=[CHB11H5Cl6]−, [CHB11Cl11]−) with Me3Si‐E‐SiMe3. In the reaction of Me3Si‐O‐SiMe3 with [Me3Si‐H‐SiMe3][B(C6F5)4], a ligand exchange was observed in the [Me3Si‐H‐SiMe3]+ cation leading to the surprising formation of the persilylated [(Me3Si)2(Me2(H)Si)O]+ oxonium ion in a formal [Me2(H)Si]+ instead of the desired [Me3Si]+ transfer reaction. In contrast, the expected homoleptic persilylated [(Me3Si)3S]+ ion was formed and isolated as [B(C6F5)4]− and [CB]− salt, when Me3Si‐S‐SiMe3 was treated with either [Me3Si‐H‐SiMe3][B(C6F5)4] or Me3Si[CB]. However, the addition of Me3Si[CB] to Me3Si‐O‐SiMe3 unexpectedly led to the release of Me4Si with simultaneous formation of a cyclic dioxonium dication of the type [Me3Si‐μO‐SiMe2]2[CB]2 in an anion‐mediated reaction. DFT studies on structure, bonding and thermodynamics of the [(Me3Si)3E]+ and [(Me3Si)2(Me2(H)Si)E]+ ion formation are presented as well as mechanistic investigations on the template‐driven transformation of the [(Me3Si)3E]+ ion into a cyclic dichalconium dication [Me3Si‐μE‐SiMe2]22+. [ABSTRACT FROM AUTHOR]

A metal‐free, photoinduced aerobic tandem amine dehydrogenation/Povarov cyclization/aromatization reaction between N‐aryl glycine esters and indoles leads to tetracyclic 11H‐indolo[3,2‐c]quinolines under mild conditions and with high yields. The reaction can be performed by using molecular iodine along with visible light, or by combining an organic photoredox catalyst with a halide anion. Mechanistic studies reveal that product formation occurs through a combination of radical‐mediated oxidation steps with an iminium ion or N‐haloiminium ion [4+2]‐cycloaddition, and the N‐heterocyclic products constitute new analogues of the antiplasmodial natural alkaloid isocryptolepine. [ABSTRACT FROM AUTHOR]

The total synthesis of a new dabigatran derivative featuring a tosyl protecting group at the amidine group of dabigatran was explored. During the course of this work, different new synthetic pathways towards dabigatran intermediates are investigated and known concepts revisited. In this context, it was found that, in our hands, a published synthesis did not work as reported. Part of the synthetic strategy presented herein is an amidine‐selective tosylation of 4‐aminobenzamidine. Furthermore, two new dabigatran derivatives exhibit thrombin inhibition activity. [ABSTRACT FROM AUTHOR]

The reactivity of the four‐membered NP3 ring system [RN(μ‐PCl)2PR] (R=Mes*=2,4,6‐tri‐tert‐butylphenyl) towards Lewis acids, Lewis bases, and reducing agents was investigated. Comparisons with the literature‐known, analogous cyclic compounds [ClP(μ‐NR)]2 (R=Ter=2,6‐dimesitylphenyl) and [ClP(μ‐PR)]2 (R=Mes*) are drawn, to obtain a better systematic understanding of the reactivity of cyclic NP species. Apart from experimental results, DFT computations are discussed to further the insight into bonding and electronic structure of these compounds. [ABSTRACT FROM AUTHOR]

A variety of thienoquinolones were synthesized from readily accessible thiophene derivatives by regioselective acylations and subsequent two‐fold Buchwald–Hartwig–amination. This cyclization allows a convenient synthesis of biologically and pharmaceutically important thienoquinolones. Several thienoquinolones were synthesized in good to very good yields. The optical properties of the products were studied in detail. [ABSTRACT FROM AUTHOR]

A convenient synthesis of various benzoacridines and benzophenanthridines from readily available dihalogenated quinolines is reported. The synthesis is based on regioselective Suzuki and Sonogashira reactions followed by Brønsted acid‐mediated cycloisomerization. The developed methodology is highly modular and allows the construction of various ring systems and substitution patterns in high yields. The optical and electrochemical properties of selected derivatives were investigated. [ABSTRACT FROM AUTHOR]