Assessing Alkali-Metal Effects in the Structures and Reactivity of Mixed-Ligand Alkyl/Alkoxide Alkali-Metal Magnesiates

Advancing the understanding of using alkali-metal alkoxides as additives to organomagnesium reagents in Mg−Br exchange reactions, a homologous series of mixed-ligand alkyl/alkoxide alkali-metal magnesiates [MMg(CH₂SiMe₃)₂(dmem)]₂ [dmem=2-{[2-(dimethylamino)ethyl]methylamino} ethoxide; M=Li, 1 ; Na, 2 ; (THF)K, 3 ] has been prepared. Structural and spectroscopic studies have established the constitutions of these heteroleptic/heterometallic species, which are retained in arene solution. Evaluation of their reactivity towards 2-bromoanisole has uncovered a marked alkali-metal effect with potassium magnesiate 3 being the most efficient of the three ate reagents. Studies probing the constitution of the exchange product from this reaction suggest that the putative [KMgAr₂(dmem)]₂ (Ar=o-OMe−C₆H₄) intermediate undergoes redistribution into its single metal components [KAr]_n and [MgAr(dmem)]₂ ( 5 ). This process can be circumvented by using a different potassium alkoxide containing an aliphatic chain such as KOR’ (R’=2-ethylhexyl) which undergoes co-complexation with Mg(CH₂SiMe₃) to give [KMg(CH₂SiMe₃)₂(OR’)]₂ ( 7 ). This ate, in turn, reacts quantitatively with 2-bromoanisole furnishing [KMgAr₂(OR’)]₂ ( 9 ) which is stable in solution as a bimetallic compound. Collectively this work highlights the complexity of these alkali-metal mediated Mg−Br exchange reactions, where each reaction component can have a profound effect not only on the success of the reaction; but also the stability of the final metalated intermediates prior to their electrophilic interception.     

Ion-Exchange Properties of Alkali-Metal Redox-Intercalated Vanadyl Phosphate

Ion exchange of alkali metals in M_xVOPO₄·yH₂O (M=H, Na, K, Rb, Cs) is reported. The role of valence, size, and affinity of the cations in the exchange process is discussed. The interlayer distance in the H_1-xK_xVOPO₄·yH₂O system is discussed in terms of finite layer rigidity theory. Different behavior is observed for K_xNa_1-xVOPO₄·yH₂O dependening on the starting compound used. When potassium in KVOPO₄·H₂O is exchanged for Na⁺, one phase compound is formed. In contrast, K_xNa_1-xVOPO₄·yH₂O formed from NaVOPO₄·H₂O and K⁺ is a multiphase system. Ion exchange does not proceed when exchanging ions differ distinctly from each other in size, e.g., sodium and cesium.     

Complex Formation Between Cystine and Alkali-Metal Cations

Complex formation between cystine and lithium, sodium, and potassium ions was investigated by measuring the electromotive force (emf) of galvanic cells involving the glass electrode for hydrogenion. All measurements were performed at 25^°C and in 3.00—mol-dm^-3 N(CH₃)₄Cl, as a constant ionic medium. The solubility of cystine was increased by performing the measurements in acid and alkaline solutions. A series of measurements was made employing an ion-specific electrode for the sodium ion. Experimental data were explained by assuming the formation of species of the type ML and M₂L, i.e., mononuclear in cystine and mono- and binuclear species in alkaline cations. The respective stability constants were determined.     

Die Kristallstruktur von Bariumamid,Ba(NH2)2

The Crystal Structure of Barium Amide, Ba(NH₂)₂ Single crystals of barium amide can be obtained by the reaction of barium metal with ammonia during long times. At ? 70° C Ba reacts with the solvent very slowly. The resulting amide then is well crystallized. Crystals can also be grown at 125° C in a temperature grakient. In both cases 3 to 4 months are necessary to get crystals of about 0.1 mm in diameter. Barium amide is monoclinic a = 8.951 Å, b = 12.67 Å, c = 7.037 Å, und β = 123.5° with 8 formula units. The space group is Cc. All atoms occupy the general position. The structure of Ba(NH₂)₂ shows two different Ba atoms with respect to their surrounding. One of them is coordinated irregularly by 8 amide ions, the other by 7 amide ions. The nitrogen atoms have 11 neighbours to each other. This means, that they are relatively close packed. Barium amide has a coorkination type structure, whereas the low symmetry of the arrangement of the different ions may be explained by the dipole chracter of the anion, and by packing effects.     

Excited-state intramolecular proton transfer (ESIPT) fluorescence from 3-amidophthalimides displaying RGBY emission in the solid state

Fluorescence properties of phthalimide derivatives (1) incorporating sulfonamide and acetamide functionalities at the 3-position were investigated both in solution and in the solid states to reveal the effects of the amide functionalities on the fluorescence properties. In the solid state, sulfonamides 1a and 1b, respectively, gave off red (λ^F_max 595?nm) and green (λ^F_max 537?nm) emission through an ESIPT process. Acetamides 1c and 1d, respectively displayed blue (λ^F_max 432?nm) and yellow (λ^F_max 560?nm) emission. Through simply modifying the amide functionality, phthalimide 1 displayed multicolor RGBY emission in the solid state.     

One‐pot synthesis and characterization of hyperbranched poly(ester‐amide)s from commercially available dicarboxylic acids and multihydroxyl secondary amines

A convenient and cost‐effective strategy for synthesis of hyperbranched poly(ester‐amide)s from commercially available dicarboxylic acids (A₂) and multihydroxyl secondary amine (CB₂) has been developed. By optimizing the conditions of model reactions, the AB₂‐type intermediates were formed dominantly during the initial reaction stage. Without any purification, the AB₂ intermediate was subjected to thermal polycondensation in the absence of any catalyst to prepare the aliphatic and semiaromatic hyperbranched poly(ester‐amide)s bearing multi‐hydroxyl end‐groups. The FTIR and ¹H NMR spectra indicated that the polymerization proceeded in the proposed way. The DBs of the resulting polymers were confirmed by a combination of inverse‐gated decoupling ¹³C NMR, and DEPT‐135 NMR techniques. The DBs of the hyperbranched poly(ester‐amide)s were in the range of 0.44–0.73, depending on the structure of the monomers used. The hyperbranched polymers exhibited moderate molecular weights with relatively broad distributions determined by SEC. All the polymers displayed low inherent viscosity (0.11–0.25 dL/g) due to the branched nature. Structural and end‐group effects on the thermal properties of the hyperbranched polymers were investigated using DSC. The thermogravimetric analysis revealed that the resulting polymers exhibit reasonable thermal stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5077–5092, 2008     

trans‐(Cl)‐[Ru(5,5′‐diamide‐2,2′‐bipyridine)(CO)2Cl2]: Synthesis,Structure, and Photocatalytic CO2 Reduction Activity

A series of trans‐(Cl)‐[Ru(L)(CO)₂Cl₂]‐type complexes, in which the ligands L are 2,2′‐bipyridyl derivatives with amide groups at the 5,5′‐positions, are synthesized. The C‐connected amide group bound to the bipyridyl ligand through the carbonyl carbon atom is twisted with respect to the bipyridyl plane, whereas the N‐connected amide group is in the plane. DFT calculations reveal that the twisted structure of the C‐connected amide group raises the level of the LUMO, which results in a negative shift of the first reduction potential (E_p) of the ruthenium complex. The catalytic abilities for CO₂ reduction are evaluated in photoreactions (λ>400 nm) with the ruthenium complexes (the catalyst), [Ru(bpy)₃]²⁺ (bpy=2,2′‐bipyridine; the photosensitizer), and 1‐benzyl‐1,4‐dihydronicotinamide (the electron donor) in CO₂‐saturated N,N‐dimethylacetamide/water. The logarithm of the turnover frequency increases by shifting E_p a negative value until it reaches the reduction potential of the photosensitizer.     

Synthesis of various arylated trifluoromethyl substituted indanes and indenes,and study of their biological activity

A series of 1-trifluoromethyl substituted indanes and indenes bearing aryl groups in positions 1 and/or 3 of the indane core have been synthesized mainly by electrophilic cyclization and arylation of the corresponding trifluoromethylated allyl and propargyl alcohols. The distinctly lipophilic compounds thus obtained were tested against various components of human endocannabinoid system. None of the compounds displayed affinity toward CB₁ or CB₂ receptors. Two compounds inhibited monoacylglycerol lipase (MAGL) and three compounds showed inhibition of anandamide (AEA) uptake. The latter can be related to the low-micromolar inhibition of fatty acid amide hydrolase (FAAH) inhibition displayed by one of these compounds.     

New amino acid based biodegradable poly(ester amide)s via bis-azlactone chemistry

Abstract

Three new classes of the amino acid based biodegradable (AABB) polymers were synthesized via step growth polymerization of bis-azlactones and amino acid based diamine-diesters with activated fatty diester and alkylenediamine: a) poly(ester amide)s (PEAs) were obtained by polymerization of bis-azlactones with diamine-diesters, b) hydrophobically modified co-poly(ester amide)s (co-PEAs) were synthesized by copolymerization of activated fatty diacid diester and bis-azlactones with diamine-diesters, and c) poly(ester amide-co-amide)s (PEA-co-PAs) were obtained by copolymerization of alkylene diamine and diamine-diesters with bis-azlactones. The new poly(ester amide)s showed relatively low-molecular-weights (M_w within 2,800–19,600?Da, GPC in DMF), whereas the new co-poly(ester amide)s and poly(ester amide-co-amide)s exhibited high-molecular-weights (M_w within 40–100?kDa) leading to good mechanical properties. Incorporation of the bis-azlactone fragments into the poly(ester amide)s backbone increased hydrophobicity and thermal stability, whereas incorporation of diamine-diester units into the backbone of the bis-azlactone based polyamides rendered them biodegradable. Synthesized AABB polymers are potential candidates for constructing resorbable surgical and pharmaceutical devices.     

Bistable or Oscillating State Depending on Station and Temperature in Three‐Station Glycorotaxane Molecular Machines

High‐yield, straightforward synthesis of two‐ and three‐station [2]rotaxane molecular machines based on an anilinium, a triazolium, and a mono‐ or disubstituted pyridinium amide station is reported. In the case of the pH‐sensitive two‐station molecular machines, large‐amplitude movement of the macrocycle occurred. However, the presence of an intermediate third station led, after deprotonation of the anilinium station, and depending on the substitution of the pyridinium amide, either to exclusive localization of the macrocycle around the triazolium station or to oscillatory shuttling of the macrocycle between the triazolium and monosubstituted pyridinium amide station. Variable‐temperature ¹H NMR investigation of the oscillating system was performed in CD₂Cl₂. The exchange between the two stations proved to be fast on the NMR timescale for all considered temperatures (298–193 K). Interestingly, decreasing the temperature displaced the equilibrium between the two translational isomers until a unique location of the macrocycle around the monosubstituted pyridinium amide station was reached. Thermodynamic constants K were evaluated at each temperature: the thermodynamic parameters ΔH and ΔS were extracted from a Van′t Hoff plot, and provided the Gibbs energy ΔG. Arrhenius and Eyring plots afforded kinetic parameters, namely, energies of activation E_a, enthalpies of activation ΔH^≠, and entropies of activation ΔS^≠. The ΔG values deduced from kinetic parameters match very well with the ΔG values determined from thermodynamic parameters. In addition, whereas signal coalescence of pyridinium hydrogen atoms located next to the amide bond was observed at 205 K in the oscillating rotaxane and at 203 K in the two‐station rotaxane with a unique location of the macrocycle around the pyridinium amide, no separation of ¹H NMR signals of the considered hydrogen atoms was seen in the corresponding nonencapsulated thread. It is suggested that the macrocycle acts as a molecular brake for the rotation of the pyridinium–amide bond when it interacts by hydrogen bonding with both the amide NH and the pyridinium hydrogen atoms at the same time.     

Strong deshielding in aromatic isoxazolines

Very strong proton deshielding was found in di/tri‐aromatic isoxazoline regioisomers prepared from acridin‐4‐yl dipolarophiles and stable benzonitrile oxides (BNO). Three alkenes, (acridin‐4‐yl)‐CH?CH‐R (R = COOCH₃, Ph, and CONH₂), reacted with three BNO dipoles (2,4,6‐trimethoxy, 2,4,6‐trimethyl, 2,6‐dichloro) to give pairs of target isoxazolines with acridine bound to C‐4 or C‐5 carbon of the isoxazoline (denoted as 4‐Acr or 5‐Acr). Regioselectivity was dependent on both the dipolarophile and dipole character. The ester and amide dipolarophile displayed variable regioselectivity in cycloadditions whereas the styrene one afforded prevailing 4‐Acr regioisomers. 2,4,6‐Trimethoxy‐BNO was most prone to form 5‐Acr isoxazolines while mesitonitrile oxide gave major 4‐Acr isoxazolines. Basic hydrolysis of the amide cycloadduct led to an unexpected isoxazolone product. The structure of the target compounds was studied by NMR, MS, and X‐ray crystallography. Copyright © 2015 John Wiley & Sons, Ltd.     

Chemical upcycling of poly(lactide) plastic waste to lactate ester,lactide and new poly(lactide) under Mg-catalysis condition

Chemical upcycling of end-of-life poly(lactide) plastics to lactide, lactate ester and new poly(lactide) has been achieved by using magnesium bis[bis(trimethylsilyl)amide] [Mg(HMDS)₂] as promoter. Mg(HMDS)₂ showed high efficiency in l-lactide polymerization and poly(lactide) depolymerization. Mg(HMDS)₂/Ph₂CHOH catalytic system displayed high ring-opening selectivity and the characteristic of immortal polymerization. Taking advantage of transesterification, depolymerizations of end-of-life poly(lactide) plastics to lactate ester (polymer to value-added chemicals) and lactide (polymer to monomer) were achieved with high yields. Besides, a new “depolymerization-repolymerization” strategy was proposed to directly transform poly(lactide) into new poly(lactide). This work provides a theoretical basis for the design of polymerization and depolymerization catalysts and promotes the development of degradable polymers.     

[F]Fluoromethyl iodide ([F]FCH2I): preparation and reactions with phenol, thiophenol, amide and amine functional groups

In this study, we report the synthesis and reactivity of [¹⁸F]fluoromethyl iodide ([¹⁸F]FCH₂I) with various nucleophilic substrates and the stabilities of [¹⁸F]fluoromethylated compounds. [¹⁸F]FCH₂I was prepared by reacting diiodomethane (CH₂I₂) with [¹⁸F]KF, and purified by distillation in radiochemical yields of 14-31% (n = 25). [¹⁸F]FCH₂I was stable in organic solvents commonly used for labeling and aqueous solution with pH 1-7, but was unstable in basic solutions. [¹⁸F]FCH₂I displayed a high reactivity with various nucleophilic substrates such as phenol, thiophenol, amide and amine. The [¹⁸F]fluoromethylated compounds synthesized by the reactions of phenol, thiophenol and tertiary amine with [¹⁸F]FCH₂I were stable for purification, formulation and storage. In contrast, the [¹⁸F]fluoromethylated compounds synthesized by the reactions of primary or secondary amines, and amide with [¹⁸F]FCH₂I were too unstable to be detected or purified from the reaction mixtures. Defluorination of these [¹⁸F]fluoromethyl compounds was a main decomposition route.     

Studies on the Selective Reduction of the Amide Link of Acyclic and Macrocyclic Amidoketals: Unexpected Cleavage and trans‐Acetalization with Red‐Al®

Selective reduction of the amide moiety of acyclic and macrocyclic amidoketals was studied in presence of various reagents (BH₃ · Me₂S, iBuAlH₂, Red‐Al^®, LiAlH₄). The best results were obtained with lithium aluminium hydride in the presence of triethylamine traces, whereas borane dimethyl sulfide gave rise to a partial ketal reduction of the acyclic compound and Red‐Al^® to a cleavage of the macrocyclic molecule accompanied by an unexpected trans‐acetalization.     

Luminescent Study on Nd3+ Complexes Containing Carboxylate‐Dithiolene and Alkoxide‐Dithiolene Ligands

Reaction of ligand L H₂ (4,5‐bis[carboxymethylthio]‐1,3‐dithiol‐2‐thione) with neodymium silyl‐amide (Nd[N(TMS)₂]₃; TMS= ‐SiMe₃), in a ratio 2:1, yields a neodymium‐dithiolene‐carboxylato complex ( 1 ) (Nd( L H) L ). Similarly, reaction of 2 equivalents of L′ H₂ (4,5‐bis[2′‐hydroxyethyl)thio]‐1,3‐dithiol‐2‐thione) and one equivalent of neodymium silyl‐amide (Nd[N(TMS)₂]₃) allowed the isolation of complex 2 , with a ligand:metal ratio of 3:2. ATR‐IR spectrum of 1 displays a broad band characteristic of an OH group showing that one carboxylate group remains protonated. Emission spectrum of complex 1 under excitation in the visible region (at 360 nm i.e. on the ligand) displayed typical emission bands of the Nd³⁺, showing that energy transfer from the ligand to the lanthanide was achieved (i.e. “antenna effect”). No significant quenching from the remaining –OH group was detected. In the case of complex 2 , the main emission bands characteristic of the Nd³⁺ ion have been observed, by excitation at 495 nm.     

Synthesis and Crystal Structures of Sodium and Calcium ­Complexes with the Ligand N‐(2,6‐Dimethylphenyl)diphenylphosphinic Amide

The sodium complex [{Ph₂P(O)NH(2,6‐Me₂C₆H₃)}Na{Ph₂P(O)N(2,6‐Me₂C₆H₃)}]₂ ( 2 ) with the ligand N‐(2,6‐dimethylphenyl)diphenylphosphinic amide was synthesized involving the reaction of the neutral ligand [Ph₂P(O)NH(2,6‐Me₂C₆H₃)] ( 1 ) and sodium bis(trimethylsilyl)amide in toluene at 60 °C. The calcium complex [{Ph₂P(O)NH(2,6‐Me₂C₆H₃)CaI(THF)₃}I] ( 3 ) was obtained by the reaction between the neutral ligand 1 and anhydrous calcium diiodide in THF at ambient temperature. The solid‐state structures of the complexes were established by single‐crystal X‐ray diffraction analysis. In the solid‐state structure of 2 , the sodium ion is coordinated through the chelation of oxygen atom attached to the phosphorus atom. Two different P–N and P–O bond lengths are observed, which indicates that one ligand moiety is anionic, whereas the second one is neutral. In the solid‐state structure of 3 , the calcium atom adopts distorted octahedral arrangement through the ligation of two phosphinic amide ligands, three THF molecules, and one iodide ion.     

配合物(ArO)2Yb(NPh2)2K(THF)4(Ar=C6H2-t-Bu3-2,4,6)的合成、分子结构和催化行为

Reaction of anhydrous YbC13 with 2 equiv, of sodium 2,4,6-tri-tert-butylphenoxide (ArONa, Ar=C6H2-t-Bu3-2,4,6) and 2 equiv, of potassium diphenyl amide in THF afforded the first bis(aryloxo) amido-lanthanide complex of (ArO)2Yb(NPh2)2K(THF)4 (1). In 1, the ytterbium and potassium were bridged via diphenyl amido ligands.The ytterbium metal center was coordinated to two oxygen atoms of aryloxide ligands and two nitrogen atoms of diphenyl amido ligands in a conventional distorted tetrahedral fashion, while the potassium interacted in η^2-fashion with two phenyl rings of the diphenyl amido ligands besides four THF molecules. 1 displayed moderate catalytic activities for the polymerization of methyl methacrylate and acrylonitrile.     

One- or two-dimensional organometallic arrays containing PdIr2(μ3-S)2 mixed-metal sulfido cluster units connected via the nicotinamide or isonicotinamide ligands on their Pd sites through hydrogen-bonding interactions

Mixed-metal sulfido cluster [(PdCl₂)(Cp*Ir)₂(μ₃-S)₂] (Cp*=η⁵-C₅Me₅) dissolved in CH₂Cl₂ reacted with two equivalent of L (L=nicotinamide, isonicotinamide, or N-methylnicotinamide) in the presence of AgBF₄ to give the cationic clusters [(PdL₂)(Cp*Ir)₂(μ₃-S)₂][BF₄]₂. The single-crystal X-ray diffraction studies of these products have disclosed that in the solid state the PdIr₂S₂ cores are self-assembled to form one-dimensional chains through the intermolecular hydrogen-bonding between the amide groups for L=nicotinamide or two-dimensional sheets via the hydrogen-bonding between the amide groups and the BF₄ anions for L=isonicotinamide, whereas no organization of the cluster cores is observed for L=N-methylnicotinamide.     

The Synthesis of Amide Dendritic Gelators and its Self-assembly Behavior in MMA

Three kinds of amide dendritic gelators, G₁-C₁₂-G₁, G₂-C₁₂-G₂ and gelator-1, were synthesized, and their self-assemble behavior in methyl methacrylate (MMA) was firstly investigated. The structures of the amide dendritic gelators were confirmed by ¹H-NMR and Mass spectra (MS). The gelation ability of the amide dendritic gelators was researched through tube inversion experiment, the results of which showed that different structures led to quite different gelation ability, including gel-sol temperature and critical concentration to form a stable gel. SEM experiments showed that three kinds of gelator formed different gel morphologies in MMA, all of which were nanoscale gel. All the three amide dendritic gelators could not only form stable gel network at certain temperature with different concentrations in MMA, but also in each case, an optically transparent gel was formed, which indicated dendrimers in the MMA had a good compatibility.     

From α‐carbamoyl‐α‐cyano­oxiranes to 3‐halogenopyruv­amides

The crystal structures of the first stable α‐diol from the α‐halogenopyruv­amide series, 3‐chloro‐2,2‐di­hydroxy‐3‐phenyl­propan­amide, C₉H₁₀­ClNO₃, and three products [3‐(4‐chloro­phenyl)‐2‐cyano‐2,3‐epoxy­propan­amide, C₁₀H₇­ClN₂O₂, 3‐bromo‐2‐cyano‐2‐hydroxy‐3‐p‐tolyl­propan­amide, C₁₁H₁₁Br­N₂O₂, 3‐bromo‐2‐oxo‐3‐p‐tolyl­propan­amide, C₁₀H₁₀­BrNO₂] obtained during the systematic synthesis of α‐halogenopyruv­amides are reported. The crystal structures are dominated by hydrogen bonds involving an amide group. The stability of the geminal diol could be ascribed to hydrogen bonds which involve both hydroxyl groups.