Thermolysis Conditions Research Articles

Synthesis of N2-Substituted 1,2,3-Triazoles.

We present a novel synthetic approach for the synthesis of the 1,2,3-triazole core, with a particular focus on the direct and regioselective synthesis of the synthetically more challenging triazoles having additional substituents at the N2 nitrogen atom. Through treatment of readily accessible geminal diazides with organic hydrazines under mild thermolysis conditions, a broad spectrum of N2-alkyl- and N2-aryl-1,2,3-triazoles are easily generated. For example, geminal diazides derived from ketoesters, ketoamides, and ketones were converted under the reaction conditions. The product structures were confirmed via NMR as well as single-crystal structure analysis.

Imidazo[2,1-b][1,3,4]thiadiazoles: Microwave-assisted synthesis, gas phase thermolysis and integrative mechanistic approach

The present study, deals with the synthesis of 2-substituted-6-phenyl-imidazo[2,1-b][1,3,4]thiadiazoles from 2-amino-5-substituted-1,3,4-thiadiazoles and 2-bromo-1-phenylethanone, which was carried out applying a microwave-assisted aqueous procedure. Furthermore, the gas-phase thermal behaviour of these imidazothiadiazoles in flash vacuum pyrolysis reactions has been studied. It has been shown that thermolysis conditions induce thiadiazole fragmentation to give indole-carbonitriles and other nitriles. The quantum chemical calculations support a stepwise mechanism for the fragmentation of imidazothiadiazoles to afford products.

Cyclocondensation of 2-(α-Diazoacyl)-2H-azirines with Amidines in Diazo Synthesis of Functionalized Naphtho[1,2-d]imidazoles.

A diazo approach toward functionalized naphtho[1,2-d]imidazole derivatives has been developed. It involved a new reaction of arylamidines with 2-(α-diazoacyl)-2H-azirines giving 5-aryl-4-(α-diazoacyl)-1H-imidazoles under mild conditions in good yields. The mechanism of annulation of azirines with amidines is discussed based on DFT calculations. The reaction proceeds in an unusual manner by cleavage of the azirine C-C bond, allowing for the transfer of the aryl substituent from the arylamidine to the proper position of the key intermediate of naphtho[1,2-d]imidazole synthesis. Under thermolysis conditions, 5-aryl-4-(α-diazoacyl)-1H-imidazoles undergo Wolff rearrangement followed by the selective 6π-cyclization of transient ketene to form 3H-naphtho[1,2-d]imidazoles bearing various substituents in the positions 2,3,4,5,7,8,9. Additionally, variation of the substituents at position 5 of naphtho[1,2-d]imidazoles is possible through the formation of triflates and subsequent cross-coupling reactions. One more heterocyclic pharmacophoric skeleton, 3H-furo[3',2':3,4]naphtho[1,2-d]imidazole, was easily constructed from methyl 5-hydroxy-3H-naphtho[1,2-d]imidazole-4-carboxylates in a one-pot mode using O-alkylation with phenacyl bromides followed by base-induced intramolecular acyl substitution at room temperature with high yields.

Asymmetric Synthesis of Nidulalin A and Nidulaxanthone A: Selective Carbonyl Desaturation Using an Oxoammonium Salt.

Nidulaxanthone A is a dimeric, dihydroxanthone natural product that was isolated in 2020 from Aspergillus sp. Structurally, the compound features an unprecedented heptacyclic 6/6/6/6/6/6/6 ring system which is unusual for natural xanthone dimers. Biosynthetically, nidulaxanthone A originates from the monomer nidulalin A via stereoselective Diels-Alder dimerization. To expedite the synthesis of nidulalin A and study the proposed dimerization, we developed methodology involving the use of allyl triflate for chromone ester activation, followed by vinylogous addition, to rapidly forge the nidulalin A scaffold in a four-step sequence which also features ketone desaturation using Bobbitt's oxoammonium salt. An asymmetric synthesis of nidulalin A was achieved using acylative kinetic resolution (AKR) of chiral, racemic 2H-nidulalin A. Dimerization of enantioenriched nidulalin A to nidulaxanthone A was achieved using solvent-free, thermolytic conditions. Computational studies have been conducted to probe both the oxoammonium-mediated desaturation and (4 + 2) dimerization events.

Водородные и галогенные связи в трииодаминобензоатах азотистых оснований

The crystalline structures of three organic salts of triiodoaminobenzoic acid (1–3) and triiodoaminobenzoic acid monohydrate (4) are described, the structural features are established by the X-ray diffraction method. Compound 1: C20H19I6N3O6, М 1158.78; monoclinic syngony, space group Сс; cell parameters: a = 32.0782(10), b = 9.5284(3), c = 9.3745(3) Å;  = 90, β = 90,0(1),  = 90 deg.; V = 2865.35(16) Å3, Z = 4, ρcalc. = 2.684 g/cm3. Compound 2: C16H15I6N3O4, М 1074.71; monoclinic syngony, space group P21/c; cell parameters: a = 8.990(5), b = 28.541(11), c = 9.945(5) Å;  =  = 90, β = 91.23(2) deg.; V = 2551(2) Å3, Z = 4, ρcalc. = 2.798 g/cm3. Compound 3: C17H17I3N2O4, М 694.03; monoclinic syngony, space group I2/a; cell parameters: a = 36.02(2), b = 7.254(5), c = 16.468(9) Å;  =  = 90, β = 105.29(2) deg.; V = 4150(4) Å3, Z = 8, ρcalc. = 2.222 g/cm3. Compound 4: C7H6I3NO3, М 532.83; rhombic syngony, space group Iba2; cell parameters: a = 30.2146(4), b = 13.9830(2), c = 5.80740(10) Å;  = β =  = 90 deg.; V = 2453.57(6) Å3, Z = 8, ρcalc. = 2,885 g/cm3. The crystalline structure of two salts and triiodoaminobenzoic acid monohydrate is distinguished both by domination of hydrogen bonds and multiple halogen bonds. However, the 7-methylquinoline salt is devoid of halogen bonds due to peculiarities of the stack packaging of flat molecules. For two compounds (3 and 4), the features of their thermolysis by thermal analysis (in argon atmosphere) are determined: at the first stage (52 and 73 °C, respectively), the loss of crystallization water occurs; at 700 ° C under the thermolysis conditions of both compounds the decomposition product is glass carbon.

Peroxidation and Skeletal Rearrangement for the Synthesis of Dioxole‐2‐Carboxamide Derivatives under Continuous‐Flow Conditions

AbstractHerein, we report peroxidative dearomatization of 2‐naphthol and C−H peroxidation of 3‐arylbenzofuran‐2‐ones with 66–94% yield under catalyst‐free conditions using continuous flow module. Besides, an approach for the synthesis of N‐substituted‐2‐phenylbenzo[d][1,3]dioxole‐2‐carboxamide has been achieved via the skeletal rearrangement of peroxybenzofuranone using amines in the absence of catalyst under continuous flow. The mechanistic study suggests that this peroxidation reaction proceeds via free radical formation under thermolytic conditions.

Efficient electrocatalytic oxygen reduction reaction of thermally optimized carbon black supported zeolitic imidazolate framework nanocrystals under low-temperature.

Turning commercially available low-cost conducting carbon black materials into functional electrocatalytic electrode media using simple surface chemical modification is a highly attractive approach. This study reports on remarkably enhanced oxygen electrocatalytic activity of commercially available Ketjenblack (KB) by growing a non-precious cobalt metal-based zeolitic-imidazolate framework (ZIF-67) at room temperature in methanol solution followed by a mild thermolysis. The resulting Co@CoOx nanoparticle decorated nitrogen-doped KB derived from the optimized ZIF-67 : KB weight ratio of hybrid samples at 500-600 °C shows high performance for the oxygen reduction reaction (ORR) with impressive Eonset and E1/2 values of ∼0.90 and ∼0.83 V (vs. RHE), respectively in 0.1 M KOH electrolyte. Such ORR activity is comparable to, or better than many metal@metal-oxide-carbon based electrocatalysts synthesized under elevated carbothermal temperatures and using multicomponent/multistep chemical modification conditions. Therefore, a simple electrocatalyst design reported in this work is an efficient synthesis route that not only utilises earth-abundant carbon black but also comprises scalable room temperature synthesized ZIF-67 following mild thermolysis conditions under 600 °C.

Morphological Analysis of Poly(4,4'-oxydiphenylene-pyromellitimide)-Based Organic Solvent Nanofiltration Membranes Formed by the Solution Method.

Poly-(4,4'-oxydiphenylene) pyromellitimide or Kapton is the most widely available polyimide with high chemical and thermal stability. It has great prospects for use as a membrane material for filtering organic media due to its complete insolubility. However, the formation of membranes based on it, at the moment, is an unsolved problem. The study corresponds to the rediscovery of poly(4,4'-oxydiphenylene-pyromellitimide)-based soluble copoly(urethane-imides) as membrane polymers of a new generation. It is shown that the physical structure of PUI films prepared by the solution method becomes porous after the removal of urethane blocks from the polymer, and the pore size varies depending on the conditions of thermolysis and subsequent hydrolysis of the membrane polymer. The film annealed at 170 °C with a low destruction degree of polycaprolactam blocks exhibits the properties of a nanofiltration membrane. It is stable in the aprotic solvent DMF and has a Remasol Brilliant Blue R retention coefficient of 95%. After the hydrolysis of thermally treated films in acidic media, ultrafiltration size 66-82 nm pores appear, which leads to an increase in the permeate flow by more than two orders of magnitude. This circumstance provides opportunities for controlling the membrane polymer structure for further optimization of the performance characteristics of filtration membranes based on it. Thus, we proposed a new preparation method of ultra- and nanofiltration membranes based on poly(4,4'-oxydiphenylene-pyromellitimide) that are stable in aprotic solvents.

Cluster Growth Reactions: Structures and Bonding of Metal-Rich Metallaheteroboranes Containing Heavier Chalcogen Elements.

In an effort to synthesize cobalt-rich metallaheteroboranes from decaborane(14) analogues, we have studied the reaction of 10-vertex nido-[(Cp*Co)2B6H6E2] (Cp* = η5-C5Me5, 1: E = Se and 2: E = Te) with [Co2(CO)8] under thermolytic conditions. All of these reactions yielded face-fused clusters, [(Cp*Co)2B6H6E2{Co(CO)}(μ-CO){Co3(CO)6}] (3: E = Se and 4: E = Te). Further, when clusters 3 and 4 were treated with [Co2(CO)8], they underwent further cluster buildup reactions leading to the formation of 16-vertex doubly face-fused clusters [(Cp*Co)2B6H6E2{Co2(CO)2}(μ-CO)2{Co4(CO)8}] (5: E = Se and 6: E = Te). Cobaltaheteroboranes 3 and 4 comprise one icosahedron {Co4B6E2} and one square pyramidal {Co3B2} moiety, whereas 5 and 6 are made with one icosahedron {Co4B6E2} and two square pyramidal {Co3B2} cores. In an attempt to generate heterometallic metal-rich clusters, we have explored the reactivity of decaborane(14) analogue nido-[(Cp*Co)2B7TeH9] (7) with [Ru3(CO)12] at 80 °C, which afforded face-fused 13-vertex cluster [(Cp*Co)2B7H7Te{Ru3(CO)8}] (8). Cluster 8 is a rare example of a metal-rich metallaheteroborane in which one icosahedron {Co2Ru2B7Te} and a tetrahedron {Ru2B2} units are fused through a common {RuB2} triangular face. Further, the treatment of nido-[(Cp*Co)2B6S2H4(CH2S2)] (9) with [Fe2(CO)9] afforded 11-vertex nido-[(Cp*Co)2B6S2H4(CH2S2){Fe(CO)3}] (10). The core structure of 10 is similar to that of [C2B9H11]2- with a five-membered pentahapto coordinating face. All of the synthesized metal-rich metallaheteroboranes have been characterized by multinuclear nuclear magnetic resonance (NMR) spectroscopy, IR spectroscopy, ESI-MS, and structurally solved by single-crystal X-ray diffraction analysis. Furthermore, theoretical investigations gave insight into the bonding of such higher-nuclearity clusters containing heavier chalcogen atoms.

Synthesis, Photophysical Properties, and Aromaticity of Pyrazine-Fused Tetrazapentalenes.

Pyrazine-fused 1,2,6,6a-tetrazapentalenes (PyTeAP) are zwitterionic tricyclic compounds exhibiting an original pattern with four consecutive nitrogen atoms. They were obtained by a challenging cyclization through the formation of a N-N bond under thermolytic conditions. Ten derivatives were synthesized, and the original scaffold of PyTeAP was confirmed by single-crystal X-ray diffraction analysis of one derivative. Examination of their photophysical properties in solution revealed blue fluorescence with λem = 416-426 nm. Theoretical investigations of the aromaticity in these compounds through magnetic criteria evidenced the presence of a dominant 14-electron circuit at the periphery.

New Aspects of Ruthenium-Mediated Polyhedral Contraction of Monocarbollides

It has been shown that the interaction of tris(triphenylphosphine)ruthenium dichloride RuCl2(PPh3)3 (1) with 10-vertex monocarborane [6-Ph-nido-6-CB9H11]−[Et4N]+ (2) under mild thermolysis conditions is not selective due to the undesired coordination of ruthenium to a phenyl substituent in the carborane and phosphine ligands, giving the series of new classical and non-classical metallacarborane complexes. In contrast, the reaction of 1 and monocarborane [arachno-6-CB9H14]−[Et4N]+ (3) proceeds more selectively with the formation of the only one product, a isocloso-structured metallacarborane. The structures of two ruthenacarboranes were resolved by X-ray diffraction.

Ring-Opening Polymerization of a Bicyclic Lactone: Polyesters Derived from Norcamphor with Complete Chemical Recyclability.

Chemical recycling of polymers is an elegant approach to achieve a circular economy and address the sustainability and end-of-life issues of plastics. Herein, we report the ring-opening polymerization of a bicyclic lactone that is easily accessible from norcamphor. High molecular weight polyesters (Mn up to 164 kg mol-1) are obtained using ZnEt2 as catalyst, while the polymerizability of the monomer is good even at high temperatures. More importantly, the polymers can be completely depolymerized under thermolysis conditions to selectively recover the pristine monomer. Thus, the monomer design strategy of using ring-fused/hybridized lactones enables an innovative monomer-polymer system that shows both high polymerizability and high depolymerizability.

Terminal N2 Dissociation in [(PNN)Fe(N2 )]2 (μ-N2 ) Leads to Local Spin-State Changes and Augmented Bridging N2 Activation.

Nitrogen fixation at iron centres is a fundamental catalytic step for N2 utilisation, relevant to biological (nitrogenase) and industrial (Haber-Bosch) processes. This step is coupled with important electronic structure changes which are currently poorly understood. We show here for the first time that terminal dinitrogen dissociation from iron complexes that coordinate N2 in a terminal and bridging fashion leaves the Fe-N2 -Fe unit intact but significantly enhances the degree of N2 activation (Δν≈180 cm-1 , Raman spectroscopy) through charge redistribution. The transformation proceeds with local spin state change at the iron centre (S= →S=3 /2 ). Further dissociation of the bridging N2 can be induced under thermolytic conditions, triggering a disproportionation reaction, from which the tetrahedral (PNN)2 Fe could be isolated. This work shows that dinitrogen activation can be induced in the absence of external chemical stimuli such as reducing agents or Lewis acids.

Features of composition of heavy oil thermolysis products produced with addition of maltene fraction

A series of heavy oil (HO) thermolysis experiments in the presence of 2.5–10.0% maltene fraction recovered from oil has been performed. It has been shown that addition of maltene fraction provides HO conversion during thermolysis and a decrease in the viscosity of the products. An increase in the concentration of additive results in the decrease in coke content in the products as compared to reference experiment. Thermolysis conditions of HO of Ashal’chinskoe deposit (Russia), which give liquid products possessing viscosity of nearly 100 mm2/s in more than 97% yield in the presence of 5.0 and 10.0% of maltene fraction, have been determined, namely, 415°С and 30 atm in flow reactor.

Identification and structural characterization of potential degraded impurities of ribociclib by time of flight -tandem mass spectrometry, and their toxicity prediction

The US FDA and EMA approved Ribociclib (RIBO) to treat metastatic breast cancers in 2017. Formation of impurities during storage of any drug can significantly contribute to its overall toxicity and therapeutic efficacy, which ultimately leads to a safety concern. Over the period, it has been observed that impurities sometimes cause serious unwanted toxicity, which can even lead to withdrawal of a drug from market. Therefore, complete characterization of potential impurities is extremely important to identify molecular hot spots regarding structural changes. To the best of our knowledge, till date, the potential degraded impurities of RIBO are unknown. No study reported in literature on the structural characterization of the degradation impurities of RIBO. In this study, an ICH recommended comprehensive stress study under hydrolytic, oxidative, photolytic and thermolytic conditions was performed on RIBO. The degradation products were characterized by tandem mass spectrometry utilising time of flight mass analyzer majorly after electrospray ionisation. The atmospheric pressure chemical ionisation mode was employed in characterization of the N-oxide degradation products where Meisenheimer rearrangement occurred. A degradation product was synthesized in house and fully characterized with the help of NMR (1H NMR, 13C NMR, DEPT, 2D NMR and D2O exchange experiments). The source of formylation for the generation of degradation products was investigated employing different solvent systems. The degradation pathways were delineated by explaining the putative mechanism of degradation in various conditions. The in silico toxicity of the degradation impurities was evaluated with the help of ProTox-II toxicity prediction platform.

Catalytically active nanosized Pd9Te4 (telluropalladinite) and PdTe (kotulskite) alloys: first precursor-architecture controlled synthesis using palladium complexes of organotellurium compounds as single source precursors.

Several intermetallic binary phases of Pd–Te including Pd3Te2, PdTe, PdTe2, Pd9Te4, Pd3Te, Pd2Te, Pd20Te7, Pd8Te3, Pd7Te2, Pd7Te3, Pd4Te and Pd17Te4 are known, and negligible work (except few studies on PdTe) has been done on exploring applications of such phases and their fabrication at nanoscale. Hence, Pd(ii) complexes Pd(L1)Cl2 and Pd(L2-H)Cl (L1): Ph–Te–CH2–CH2–NH2 and L2: HO–2-C6H4–CH Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> N–CH2CH2–Te–Ph were synthesized. Under similar thermolytic conditions, complex Pd(L1)Cl2 with bidentate coordination mode of ligand provided nanostructures of Pd9Te4 (telluropalladinite) whereas Pd(L2-H)Cl with tridentate coordination mode of ligand yielded PdTe (kotulskite). Bimetallic alloy nanostructures possess high catalytic potential for Suzuki coupling of aryl chlorides, and reduction of 4-nitrophenol. They are also recyclable upto six reaction cycles in Suzuki coupling.

Di-tert-butylphosphate Derived Thermolabile Calcium Organophosphates: Precursors for Ca(H2PO4)2, Ca(HPO4), α-/β-Ca(PO3)2, and Nanocrystalline Ca10(PO4)6(OH)2.

Thermally and hydrolytically unstable di-tert-butyl phosphate (dtbp-H) has been used as synthon to prepare discrete and polymeric calcium phosphates that are convenient single-source precursors for a range of calcium phosphate ceramic biomaterials. The reactivity of dtbp-H toward two different calcium sources has been found to vary significantly, e.g., the reaction of Ca(OMe)2 with dtbp-H in a 1:6 molar ratio in petroleum ether forms a mononuclear calcium hexa-phosphate complex [Ca(dtbp)2(dtbp-H)4] (1), whereas the change of calcium source to CaH2, in a 1:2 molar ratio under otherwise similar reaction conditions, yields the calcium phosphate polymer, [Ca(μ-dtbp)2(H2O)2·H2O]n(2). Compounds 1 and 2 have been extensively characterized by various spectroscopic and analytical techniques. The solid-state structures of both 1 and 2 have been determined by single-crystal X-ray diffraction studies. In discrete molecule 1, the central calcium ion is surrounded by two anionic dtbp and four neutral dtbp-H ligands in an octahedral coordination environment. Compound 2 is a one-dimensional polymer in which adjacent calcium ions are connected through double dtbp bridges. Solid-state thermolysis of bulk 1 in air leads to the exclusive formation of calcium metaphosphate β-Ca(PO3)2 in the entire temperature range of 400-800 °C. Thermal decomposition of polymer 2, however, can be fine-tuned to produce either α-Ca(PO3)2 or β-Ca(PO3)2 depending on the thermolysis conditions employed. Although the sample sintered at 600 °C produces exclusively α-form of Ca(PO3)2, the sample annealed at 800 °C or above produces β-form. Both α- and β-forms can also be successively formed one after other by a slow heating of a freshly prepared 2 on the powder diffractometer sample holder. Additional forms of ceramic phosphates have been prepared by solvothermal conditions because of the highly labile nature of the tert-butoxy groups of dtbp in 1 and 2. Solution decomposition of either 1 or 2 in boiling toluene at 140 °C in a sealed tube produces calcium dihydrogen phosphate [Ca(H2PO4)2·H2O] as the only product in the form of single crystals. Solution thermolysis of 2 in protic solvents such as water and methanol can be biased to produce other calcium phosphate biomaterials such as hydroxyapatite [Ca10(PO4)6(OH)2]and calcium monohydrogen phosphate [Ca(HPO4)] in the presence of additional calcium precursors such as CaO and Ca(OMe)2, respectively.

On the Stability and Degradation Pathways of Venetoclax under Stress Conditions.

Venetoclax is an orally bioavailable, B-cell lymphoma-2 (BCL-2) selective inhibitor, used for the treatment of various types of blood cancers, such as chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL). In this study we investigated the degradation of venetoclax under various stress conditions including acidic, basic, oxidative, photolytic and thermolytic conditions. We isolated and identified six of its main degradation products produced in forced degradation studies. The structures of the isolated degradation products were determined by using nuclear magnetic resonance (NMR) spectroscopy, high resolution mass spectrometry (HRMS) and infrared (IR) spectroscopy. Additionally, one oxidation degradation product was identified with comparison to a commercially obtained venetoclax impurity. We proposed the key degradation pathways of venetoclax in solution. To the best of our knowledge, no structures of degradation products of venetoclax have been previously published. The study provides novel and primary knowledge of the stability characteristics of venetoclax under stress conditions. Venetoclax is currently the only BCL-2 protein inhibitor on the market. In addition to single agent treatment, it is effective in combinational therapy, so future drug development involving venetoclax can be expected. A better insight into the stability properties of the therapeutic can facilitate future studies involving venetoclax and aid in the search of new similar therapeutics.

Thermal Shrinkage Behavior of Metal–Organic Frameworks

AbstractThermal treatment of metal–organic frameworks (MOFs) as a post‐treatment approach has grown in popularity and resulted in various MOF‐derived materials. However, the widely used extreme thermolytic conditions (usually above 500 °C) lead to degradation in the well‐defined MOFs intrinsic properties. This work demonstrates that MIL‐101 calcined at medium‐temperature range (200–280 °C) partially breaks the coordination bonds that can introduce more accessible active sites, exhibiting a 10‐fold increase in oxidation activity while retaining its intrinsic structure and porosity. Another fascinating feature of MIL‐101 calcined in this temperature range is their temperature‐dependent shrinkage behavior, which is also found in many other types of MOFs. Based on different shrinkage ratios of various MOFs, yolk–shell MOFs@MOFs structures can be constructed through nonsacrificial template method. Overall, the structural and morphological evolution process of MOFs treated in the medium‐temperature range can open new horizons to develop efficient MOFs catalysts and design complex structures.

La3+ as impurity ions for the synthesis of β-NaLuF4 nanocrystals with high luminance and small size

Size-tunable (5–70 nm) and UCL-tunable β-NaLuF4 NCs were synthetized by doping impurity ions under thermolysis conditions. With the increase of impurity ions (La3+) concentration, the sizes of β-NaLuF4 NCs decreased gradually, and the shapes changed from irregularity to regularity to irregularity again. For 10 mol% La3+ doping sample, the NCs have the characteristics of monodispersity, self-assembly, small size (about 18 nm) and high luminescence efficiency, which may have potential applications in biomedical sciences.