Selective Substitution Reactions Research Articles

Exploring the Frontiers of Heterometallic Systems: the {FeW5} Octahedral Cluster Complex.

This research presents the first examples of heterometallic octahedral cluster complexes incorporating both 5d and 3d metals, specifically, tungsten and iron. The key compound, (TBA)2[FeW5Br14] (TBA = tetrabutylammonium), exhibits selective ligand substitution reactions at the iron site when exposed to various solvents. Several {FeW5}-type anions, namely, [FeW5Br14]2-, [FeW5Br13(L)]- (L = H2O, DMSO, CH3CN), and [(FeW5Br13)2O]4-, were revealed and characterized by single-crystal X-ray diffraction analysis. The redox properties of [FeW5Br14]2- were studied and compared with those of [W6Br14]2-. Density functional theory calculations demonstrated that the bonding between Fe and W atoms is fundamentally different from the bonding between 4d (Mo-Mo) or 5d (W-W) metals in isotypic {M6} clusters.

Flotation separation mechanism of malachite from calcite using the pentyl xanthate as the collector

Calcite is a commonly associated gangue mineral in oxidized copper ore, while the flotation separation of oxidized copper ore from calcite is a bottleneck technology in the utilization of carbonate-type oxidized copper ore. The present study applied the pentyl xanthate (PX) as a collector to efficiently separate malachite and calcite without any other reagents. The flotation results indicate that the PX dosage is a key factor determining the flotation separation results of malachite and calcite. When its dosage reaches 1000 mg/L, the flotation recovery rate of malachite can reach 88.7 %, while calcite is less than 5 %. The flotation test of real ore contained these two minerals further confirmed that the malachite could be separated from calcite using PX as the collector. The mechanism and characterization analysis show that the selective substitution reaction between xanthate ions and OH ions on the malachite surface could generate hydrophobic substances of copper xanthate, which largely improves the hydrophobicity of the malachite surface. This study is expected to provide theoretical and practical assistance for the efficient flotation beneficiation of low-grade marble-type copper oxide ore.

4,4′-Dicyano- versus 4,4′-Difluoro-BODIPYs in Chemoselective Postfunctionalization Reactions: Synthetic Advantages and Applications

The presence of F or CN substituents at boron in BODIPYs causes a dramatic effect on their reactivity, which allows their chemoselective postfunctionalization. Thus, whereas 1,3,5,7-tetramethyl B(CN)2-BODIPYs displayed enhanced reactivity in Knoevenagel condensations with aldehydes, the corresponding BF2-BODIPYs can experience selective aromatic electrophilic substitution (SEAr) reactions in the presence of the former. These (selective) reactions have been employed in the preparation of BODIPY dimers and tetramers, with balanced fluorescence and singlet oxygen formation, and all-BODIPY trimers and heptamers, with potential application as light-harvesting systems.

Frontispiece: Perfluoroaryl and Perfluoroheteroaryl Reagents as Emerging New Tools for Peptide Synthesis, Modification and Bioconjugation

Perfluorinated aromatics and heteroaromatics are versatile reagents for the modification of amino acids, peptides and proteins. This is principally because they undergo rapid and selective nucleophilic substitution reactions with biological nucleophiles. They are, therefore, exciting tools with which to modulate the biological activities and drug-like properties of natural and synthetic biomolecules in drug discovery and with which to append, for example, fluorescent probes in chemical biology studies. In this Minireview, Will Brittain and Chris Coxon survey the current field, discussing the synthetic incorporation of perfluoro(hetero)aromatics, the challenges posed by their physical and chemical properties, how these can be overcome, and what the future holds for these important new tools. For more information, see the Minireview on page 10.

The synthesis of 4-arylphenalenones revisited

The synthesis of 4-phenylphenalenones, a group of phytoalexins exclusive from Musa acuminata (bananas), has been revisited to extend the scope of the derivatives that can be prepared. The discovery that 4-methoxyphenalenone participates in a selective substitution reaction allowed the preparation of 4-bromophenalenone, which proved to be an efficient substrate for Suzuki cross-couplings. The results solve the previously uncovered problem of preparing electron-rich 4-heteroarylphenalenones and provide a general synthesis of this type of phytoalexins.

Highly Selective Substitution and Insertion Reactions of Silylenes in a Metal-Coordinated Polyphosphide.

Selective substitution and insertion reactions of silylenes into the cyclo-P5 ring of [Cp*Fe(η5-P5)] are reported. The selective substitution of one P atom by an isoelectronic [LSi] fragment (L = PhC(NtBu)2) leads to [(η4-P4SiL)FeCp*] and [LSi(Cl)═P-SiL(Cl)2]. To elucidate the reaction mechanism, [{LSi(N(SiMe3)2)}{(η4-P5)FeCp*}], in which the silicon atom binds to the cyclo-P5 ring, was synthesized as a model compound for the reaction intermediate. The insertion of [LSi-SiL] into the cyclo-P5 ring of [Cp*Fe(η5-P5)] resulted in [{η4-P5(SiL)2}FeCp*] featuring a cyclo-P5(SiL)2 ring, which corresponds to the largest silicon-polyphosphorus ring known in a complex.

Novel triazine-based pyrimidines suppress glomerular mesangial cells proliferation and matrix protein accumulation through a ROS-dependent mechanism in the diabetic milieu.

Diabetic nephropathy (DN) is one of the most serious complications of diabetes worldwide. It is depicted as the leading cause of end-stage renal disease. Oxidative stress plays a key role in hyperglycemia-induced DN. The preparation and characterization of novel mono-, di-, and trisubstituted-s-triazines endowed with uracil and/or thymine are described in this paper. The synthesis of the title compounds was realized through selective nucleophilic substitution reactions of cyanuric chloride with the corresponding hydrazide nucleobases. In this study, we assessed the effects of these derivatives on the progression of diabetic nephropathy. Our results show that trisubstituted-s-triazines endowed with acylhydrazides attenuate high-glucose induced glomerular mesangial cells proliferation and matrix protein accumulation in vitro. Notably, these derivatives also display anti-oxidative properties. This suggests that the novel trisubstituted-s-triazine derivatives provide renal protection through a reactive oxygen species (ROS)-dependent mechanism. Our data provide evidence that these derivatives may serve as potential therapeutic candidates in the treatment of DN.

Degradable epoxy resins based on bisphenol A diglycidyl ether and silyl ether amine curing agents

ABSTRACTA series of silyl ether amine curing agents were synthesized by selective substitution reactions of chloroalkylsilanes or the transetherification of alkoxysilanes. Crosslinked networks were prepared by mixing a stoichiometric ratio of bisphenol A diglycidyl ether (D.E.R 331) with the amine curing agents. The networks were characterized by ATR‐FTIR spectroscopy, TGA, DSC, and DMA. The onset of thermal degradation, glass transition temperatures, and storage moduli for the networks were 350 °C, 70–108 °C, and 5–25 MPa, respectively. The degradation behavior of the cured samples was monitored for 30 days in PBS, NaOH 5% (w/v), and HCl 5% (v/v) solutions and the degradation products were characterized by spectroscopic methods. The thermal, mechanical, and degradation studies indicated that crosslink density, Tg, storage modulus, and the rate of degradation were affected by the functionality of the amine curing agents and the number of hydrolyzable silyl ether bonds present per mole of curing agent. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44620.

Observation of selective surface element substitution in FeTe0.5Se0.5 superconductor thin film exposed to ambient air by synchrotron radiation spectroscopy**Project supported by the Chinese Academy of Sciences (Grant No. 1G2009312311750101) and the National Natural Science Foundation of China (Grant Nos. 11375228, 11204303, and U1332105).

A systematic investigation of oxidation on a superconductive FeTe0.5Se0.5 thin film, which was grown on Nb-doped SrTiO3 (001) by pulsed laser deposition, has been carried out. The sample was exposed to ambient air for one month for oxidation. Macroscopically, the exposed specimen lost its superconductivity due to oxidation. The specimen was subjected to in situ synchrotron radiation photoelectron spectroscopy (PES) and x-ray absorption spectroscopy (XAS) measurements following cycles of annealing and argon ion etching treatments to unravel what happened in the electronic structure and composition after exposure to air. By the spectroscopic measurements, we found that the as-grown FeTe0.5Se0.5 superconductive thin film experienced an element selective substitution reaction. The oxidation preferentially proceeds through pumping out the Te and forming Fe–O bonds by O substitution of Te. In addition, our results certify that in situ vacuum annealing and low-energy argon ion etching methods combined with spectroscopy are suitable for depth element and valence analysis of layered structure superconductor materials.

ChemInform Abstract: Copper‐Catalyzed SN2′‐Selective Allylic Substitution Reaction of gem‐Diborylalkanes.

A Cu/(NHC)-catalyzed SN2′-selective substitution reaction of allylic electrophiles with gem-diborylalkanes is reported. Different substituted gem-diborylalkanes and allylic electrophiles can be employed in this reaction, and various synthetic valuable functional groups can be tolerated. The asymmetric version of this reaction was initially researched with chiral N-heterocyclic carbene (NHC) ligands.

Copper-Catalyzed SN2′-Selective Allylic Substitution Reaction of gem-Diborylalkanes

A Cu/(NHC)-catalyzed SN2'-selective substitution reaction of allylic electrophiles with gem-diborylalkanes is reported. Different substituted gem-diborylalkanes and allylic electrophiles can be employed in this reaction, and various synthetic valuable functional groups can be tolerated. The asymmetric version of this reaction was initially researched with chiral N-heterocyclic carbene (NHC) ligands.

Preparation of t-Butyldimethylphosphine Borane and t-Butyldiethylphosphine Borane by Selective Grignard Reagent Substitution of Phosphorus Trichloride

The synthesis of differentially substituted trialkylphosphine boranes from the selective substitution reaction of Grignard reagents with phosphorus trichloride in a single reaction flask was studied. The reaction temperature, stoichiometric loading of the first equivalent of Grignard reagent and reaction time were found to be important for maximizing the yield and selectivity of the reaction. Reaction conditions were optimized to achieve maximum yield of t-butyldiethylphosphine borane. The optimized conditions were applied to the syntheses of t-butyldiethylphosphine borane and t-butyldimethylphosphine borane, which provided 60% and 62% isolated yields respectively. Products were characterized with mass spectrometry, infrared spectroscopy, 1H, 13C, and 31P nuclear magnetic resonance spectroscopy. KEYWORDS: Synthesis; Trialkylphosphine; Grignard Reagent; Selective; Substitution Reaction; t-Butyldiethylphosphine Borane; t-Butyldimethylphosphine Borane; Phosphorus Trichloride

Synthesis of Branched Alkylboronates by Copper-Catalyzed Allylic Substitution Reactions of Allylic Chlorides with 1,1-Diborylalkanes.

Reported herein is a copper-catalyzed S(N)2'-selective allylic substitution reaction using readily accessible allylic chlorides and 1,1-diborylalkanes, a reaction which proceeds with chemoselective C-B bond activation of the 1,1-diborylalkanes. In the presence of a catalytic amount of [Cu(IMes)Cl] [IMes=1,3-bis(2,4,6-trimethylphenyl)imidazole-2-ylidene] and LiOtBu as a base, a range of primary and secondary allylic chlorides undergo the S(N)2'-selective allylic substitution reaction to produce branched alkylboronates. The synthetic utilities of the obtained alkylboronates are also presented.

Multifunctional Macrocyclic Receptors as Templates for Aromatic Amino Acids: A Rare Example of a Highly Selective Multi-Input Multi-Output Chemo-"Logic Gate".

Proton-bound [M⋅H⋅G]+ diastereomeric complexes between some chiral aromatic amino acids or dipeptides (G) and a chiral multifunctional macrocyclic receptor (M=Chirabite-A) undergo, in the gas phase, highly selective substitution and addition reactions by amines, such as 2-aminobutane and piperidine. All the [M⋅H⋅G]+ complexes follow time-dependent monoexponential decays. In some cases, the kinetic curves exhibit a plateau revealing the presence of unreactive [M⋅H⋅G]+ structures. In them, the amino acid is accommodated in the macrocycle cavity in the zwitterionic form by sharing its acidic hydrogen atoms with the pyridine nitrogen atoms of the host. The same interactions are structurally inaccessible to G=dipeptides or monofunctional amines, which then can be readily released from [M⋅H⋅G]+ . When the amino acid interacts with the amidocarbonyl oxygen atoms pointing outside the macrocycle cavity, it saves the canonical structure and can be readily displaced by the amine. The Chirabite-A may act as an efficient template for aromatic amino acids by releasing them or not depending upon the amino acid configuration and the basicity of the amine. These unique properties confer to the gas-phase diastereomeric [M⋅H⋅G]+ complexes the features of multi-input multi-output chemo-"logic gates".

Tetraplatinum cluster complexes bearing hydrophilic anchors as precursors for γ-Al2O3-supported platinum nanoparticles

Tetraplatinum cluster complexes bearing hydrophilic anchors, [Pt4(μ-OCOCH3)4(μ-OCOC6H4OH-4)4] (2a), [Pt4(μ-OCOCH3)4(μ-OCOC6H4B(OH)2-4)4] (2b), and [Pt4(μ-OCOCH3)4(μ-OCOC6H4NH2-4)4] (2c), were successfully prepared by a selective substitution reaction of four in-plane acetates of [Pt4(μ-OCOCH3)8] (1) with the corresponding p-substituted benzoic acids. Solid-state structure determination of 2a revealed the 3D network structure through intermolecular hydrogen bonding between the hydroxy group of the p-hydroxybenzoate ligand and the oxygen atom of the carboxylate ligand of 2a. UV-vis analysis of 2a–c in CH3CN or CH3CN–H2O in the presence of γ-Al2O3 clearly indicated the adsorption efficiency of these platinum clusters on γ-Al2O3: 2a bearing a hydroxyl group and 2b bearing a B(OH)2 group were effectively deposited onto γ-Al2O3 from CH3CN solution, whereas less than 40% of 1 and 2c were chemically adsorbed onto γ-Al2O3. Highly dispersed and very small platinum nanoparticles (less than 1 nm) on γ-Al2O3 were obtained by thermal treatment of Pt4-deposited γ-Al2O3 at 500 °C.

ChemInform Abstract: Synthesis of 4‐(N‐Azolyl)‐3,5‐dinitropyrazoles.

AbstractThe title compounds (III) are obtained via selective substitution reaction of the nitro group at C4‐position in pyrazoles (I) through NH‐azoles.

Rational Synthesis of Supramolecular Assemblies Based on Tetraplatinum Units: Synthesis, Characterization, and Selective Substitution Reactions of Four Different Pt4 Clusters

Four different types of square-planar Pt(4) clusters, trans-[Pt(4)(μ-OCOCH(3))(6)(μ-ArNCHNAr)(2)] (2: ArNCHNAr = N,N'-diarylformamidinate), [Pt(4)(μ-OCOCH(3))(7)(μ-ArNCHNAr)] (8), cis-[Pt(4)(μ-OCOCH(3))(6)(κ(4)-N(4)-DArBp)] (9: DArBp = 1,3-bis(arylbenzamidinate)propane), and [Pt(4)Cl(2)(μ-OCOCH(3))(5)(κ(4)-N(2),P(2)-dpfam)] (13: dpfam = N,N'-bis[(2-diphenylphosphino)phenyl]formamidinate), were successfully prepared by using selective substitution reactions of in-plane acetate ligands of [Pt(4)(μ-OCOCH(3))(8)] (1), which has four in-plane and four out-plane acetate ligands, with appropriate capping ligands. Fundamental substitution reactions of the remaining in-plane acetates with benzoic acid derivatives were also investigated. All newly prepared complexes were characterized from spectral and physical data and combustion analysis. X-ray crystallographic studies of some of the clusters were also performed. Electrochemical measurements of amidinate-modified Pt(4) clusters revealed stepwise oxidation processes of the Pt(4) core due to Pt(4)(9+)/Pt(4)(8+) and Pt(4)(10+)/Pt(4)(9+). Based on the lability of the in-plane acetate ligands of the modified Pt(4) clusters, reactions of cis-[Pt(4)(μ-OCOCH(3))(6)(κ(4)-N(4)-DArBp)] (9 c: Ar = C(6)H(4)tBu-4) with ferrocenedicarboxylic acid and p-phenylenedipropionic acid resulted in the selective formation of cyclic dimers 17 and 18 and the reaction of 13 with 4,4'-biphenyldicarboxylic acid afforded a linear dimer 20. The dimers were characterized by spectral data, as well as X-ray analyses for 17 and 18. The finding of two Fe(3+)/Fe(2+) redox couples in the electrochemical measurement of dimer 17 indicated that two ferrocenyl units in dimer 17 communicated electronically.

Synthesis and screening of 2,6-diamino-substituted purine derivatives as potential cardiomyogenesis inducing agents

The synthesis of 2,6-diamino-substituted purines is reported starting from 2,6-dichloropurine via two subsequent selective nucleophilic substitution reactions. The first substitution takes place selectively in 6-, the second in 2-position. The compounds were synthesized as structural analogs of reversine, a substance which was reported to possess the ability to de-differentiate lineage- committed cells into progenitor cells which then can be differentiated into other cell types such as adipocytes or osteoblasts. The obtained compounds were tested regarding their potential to support cardiomyogenic cell differentiation based on preliminary findings that reversine also showed some activity in this regard.

ChemInform Abstract: TiCl4‐Activated Selective Nucleophilic Substitutions of tert‐Butyl Alcohol and Benzyl Alcohols with π‐Donating Substituents.

Abstract TiCl4-activated selective nucleophilic substitution reactions of tert-butyl alcohol and benzyl alcohols with π-donating substituents in the presence of primary and secondary alcohols can be carried out with various oxygen, nitrogen and carbon nucleophiles in good yields.

TiCl 4-activated selective nucleophilic substitutions of tert-butyl alcohol and benzyl alcohols with π-donating substituents

TiCl 4-activated selective nucleophilic substitution reactions of tert-butyl alcohol and benzyl alcohols with π-donating substituents in the presence of primary and secondary alcohols can be carried out with various oxygen, nitrogen and carbon nucleophiles in good yields.