Reaction Of Cis Research Articles

One‐Step Synthesis of Cyclobutene‐Annulated Fullerenes through a Cascade Reaction

AbstractThe physicochemical properties of fullerene‐based materials typically vary depending on the type and mode of addition of functional groups; therefore, developing fullerene derivatives with novel structures is imperative for further progress in materials science. In this study, we develop an efficient one‐step strategy for synthesizing cyclobutene‐annulated fullerene derivatives (cyclobutenofullerenes) and characterize their electronic properties. Despite the steric strain, cyclobutenofullerenes can be easily prepared via a one‐step reaction of C60 with a secondary propargylic phosphate. Structural analysis of the reaction intermediates suggests that the cascade reaction proceeds through a formal [2+2] cycloaddition of C60 with an allene, caused by the 1,3‐migration of the propargylic phosphate, followed by an additional 1,3‐migration and the subsequent 1,2‐elimination of the phosphodiester moiety.

Reactivity and internal dynamics in the Criegee intermediate CH2OO[sbnd]CO2 system: A rotational study

The reaction system between the simplest Criegee intermediate, CH2OO, and the greenhouse gas CO2 has been investigated by Fourier transform microwave spectroscopy. The CH2OO-CO2 weakly bound complex was identified in the rotational spectrum, where inversion doublets due to the tunnelling motion between two equivalent configurations of the complex, with CO2 located at one side or the other side of the CH2OO plane, were observed. Using a two-state torsion-rotation Hamiltonian, a complete set of rotational and centrifugal distortion constants for both tunneling states were derived. In addition, the torsional energy difference between both states could be accurately determined, being 23.9687 MHz. The non-observation of the cycloaddition reaction product is in agreement with our ab initio calculations and with previous results that concluded that the reactivity of CIs toward CO2 is measured to be quite limited.

Reactions of [60]Fullerene with Acetone under Basic Condition: Nucleophilic Ring Opening of the [5,6]-Cyclopropane in C60 and Formation of the Substituted Methano[60]Fulleroids.

The reactions of C60 with acetone were carried out under basic condition in the presence of 1.0 M TBAOH (tetra-n-butylammonium hydroxide) methanol solution and ArCH2Br (Ar = Ph or o-BrPh), where methano[60]fulleroids with a novel 1,1,4,9,9,25-configuration were obtained and structurally characterized by single crystal diffraction. The product was formed via the ring-opening reaction of the [5,6]-cyclopropane by the nucleophilic addition of MeO-, which is different from the reactions of other ketones reported previously.

A sonochemical synthesis of the piperazine-containing adducts of the C60 fullerene

We have worked out a selective and efficient mode of the synthesis of substituted and unsubstituted piperazine-containing mono-adducts of the C60 fullerene. It is based on the C60 reaction with piperazine, 2-methylpiperazine, and 2-oxopiperazine under air, room temperature and ultrasonication. The intermediate of the sonochemical reaction is radical anion C60 •–, which was detected with EPR (g = 1.9968, ΔH = 5.9 G). This intermediate is generated due to one-electron transfer from piperazine to the C60 molecule.

A novel approach for the synthesis of C60 fullerenes containing strained 2,3-dimethylenebicyclo[2,2,0]hexane fragments

A novel approach for introducing strained 2,3-dimethylenebicyclo[2,2,0]hexane structures into the C60 fullerene molecule, based on the reaction of C60 with substituted propargylamines, promoted by the Ti(Oi-Pr)4 and EtMgBr system.

Regioisomeric α-[70]fullerene-fused lactones: Synthesis, characterization and solubility difference

Two types of regioisomeric α-[70]fullerene-fused lactones were synthesized from the reaction of C70 with 2-alkylmalonates under basic conditions. The structures of the compounds were determined unambiguously by X-ray single crystal diffraction analysis, and the compounds were further characterized with HRMS, UV–vis, 1H NMR and 13C NMR spectroscopies. The reactions were followed by the in situ vis-NIR measurement to study the mechanism. Interestingly, a large solubility difference was shown between the two types of regioisomers.

The first steps toward C70 cycloadducts with a sulfur–fullerene bond: a selective sonochemical synthesis of single C70–1,4-oxathiane

C70 cycloadducts with sulfur–fullerene bond were previously unknown. We discovered that the sonochemical reaction of C70 with 1,2-hydroxythiols selectively produces the single 5,6-isomer of C70–1,4-oxathiane. The C70 •– radical anion was detected with EPR as a key intermediate of the reaction.

Sonochemical synthesis of novel C60 fullerene 1,4-oxathiane derivative through the intermediate fullerene radical anion.

We have discovered a selective and efficient method for the synthesis of previously unknown 1,9-(1',4'-oxathiano)-1,9-dihydro-(C60-Ih)[5,6]fullerene, a compound with the direct attachment of the sulfur atom to the fullerene core. The method is based on the reaction of C60 with 1,2-hydroxythiols in the presence of inorganic bases in air under ultrasonication. The significance of ultrasound has been exemplified with the comparative conventional methods. The title compound has been identified with mass-(MALDI TOF/TOF), one- and two-dimensional NMR 1H and 13C (COSY, HSQC, HMBS), IR, UV-Vis spectroscopic techniques. Using the direct EPR method, we have detected radical anion C60- (g=2.0046 and ΔH=2 G) as a key reaction intermediate of the sonochemical reaction. Based on the experimental results and quantum chemical calculations, we have proposed a mechanism for the conversion of C60 and 2-mercaptoethanol to the C60-1,4-oxathiane adduct.

Copper-Mediated Cascade Synthesis of Open-Cage Fullerenes

An open-cage fullerene bearing an eight-membered ring orifice has been synthesized in one pot by the reaction of C60 with propargylic phosphate in the presence of CuCl. The reaction cascade involves the transformation of the phosphate to the 1,3-dienyl phosphate, which enables the reaction with C60 by [4 + 2] cycloaddition to form the cyclohexene-annulated intermediate, and subsequent intramolecular syn-elimination of the phosphodiester affords the cyclohexadiene-annulated fullerene derivative as the precursor for the open-cage fullerene.

Diastereoselective Synthesis of Steroid-[60]Fullerene Hybrids and Theoretical Underpinning.

The reaction of C60 with pregnen-20-carboxaldehyde, a biologically active synthetic steroid, by using a 1,3-dipolar cycloaddition reaction (Prato's protocol) results in the formation of pyrrolidine rings bearing a new stereogenic center on the C2 of the five-membered ring. The formation of the fullerene-steroid hybrids proceeds with preference for the Re face of the 1,3-dipole, with formation of a diastereomeric mixture in 73:15 ratio. The investigation of the chiroptical properties of these conjugates allowed determining the absolute configuration of the new fulleropyrrolidines. In addition, a thorough spectroscopical study permitted to determine the structure of the two mono-cycloadducts. The electrochemical properties of the new hybrids were also evaluated by cyclic voltammetry, both systems exhibit three quasi-reversible reduction waves which are cathodically shifted in regard to the parent C60. Theoretical calculations help supporting the experimental data. A conformational study combining semiempirical methods and density functional theory has predicted the most stable diastereomer. On the basis of this agreement, a possible reaction mechanism is presented. Additionally, a molecular docking simulation has been carried out using the HIV-1 protease as receptor, thus paving the way to study the possible application of these stereoisomers in biomedicine.

Base-iodine-promoted metal-catalyst-free reactions of [60]fullerene with β-keto esters for the selective formation of [60]fullerene derivatives.

In this study, methanofullerenes and 2′,3′-dihydrofuran C60 derivatives were selectively synthesized in high yields via the reactions of C60 with β-keto esters under mild conditions by controlling the addition sequence and molar ratio of iodine and base. The structures of the products were determined by spectroscopic characterization. Moreover, a possible reaction mechanism for the selective formation of fullerene derivatives was proposed.

Insights into the Reactions of Hydroxyl Radical with Diolefins from Atmospheric to Combustion Environments.

Hydroxyl radicals and olefins are quite important from a combustion and an atmospheric chemistry standpoint. Large amounts of olefinic compounds are emitted into the earth's atmosphere from both biogenic and anthropogenic sources. Olefins make a significant share in transportation fuels (e.g., up to 20% by volume in gasoline), and they appear as important intermediates during hydrocarbon oxidation. As olefins inhibit low-temperature heat release, they have caught some attention for their applicability in future advanced combustion engine technology. Despite their importance, the literature data for the reactions of olefins are quite scarce. In this work, we have measured the rate coefficients for the reaction of hydroxyl radicals (OH) with several diolefins, namely 1,3-butadiene, cis-1,3-pentadiene, trans-1,3-pentadiene, and 1,4-pentadiene, over a wide range of experimental conditions ( T = 294-468 K and p ∼ 53 mbar; T = 881-1348 K and p ∼ 1-2.5 bar). We obtained the low- T data in a flow reactor using laser flash photolysis and laser-induced fluorescence (LPFR/LIF), and the high- T data were obtained with a shock tube and UV laser-absorption (ST/LA). At low temperatures, we observed differences in the reactivity of cis- and trans-1,3-pentadiene, but these molecules exhibited similar reactivity at high temperatures. Similar to monoolefins + OH reactions, we observed negative temperature dependence for dienes + OH reactions at low temperatures-revealing that OH-addition channels prevail at low temperatures. Except for the 1,4-pentadiene + OH reaction, which shows evidence of significant H-abstraction reactions even at low-temperatures, other diolefins studied here almost exclusively undergo addition reaction with OH radicals at the low-temperature end of our experiments; whereas the reactions mainly switch to hydrogen abstraction at high temperatures. These reactions show complex Arrhenius behavior as a result of many possible chemical pathways in such a convoluted system.

Cover Feature: Site‐selective Synthesis of β‐[70]PCBM‐like Fullerenes: Efficient Application in Perovskite Solar Cells (Chem. Eur. J. 13/2019)

Solvent polarity decides! β-[70]-PCFM fullerenes ([6,6]-Phenyl-C61-Formic acid Methyl ester) are formed as the major product in the reaction of C70 with sulfonium salts, affording a mixture of α- and β-site isomers in good yields. Amazingly, the preference for the α- or β-site isomer can be efficiently controlled by means of the solvent polarity! [70]PCFMs are very efficient in passivating the voids/pin-holes and/or deep slits in bulk heterojunction perovskite solar cells, with efficiencies around 20 %, depending on the isomeric fullerene composition. More information can be found in the Communication by S. M. Zakeeruddin, M. Grätzel, N. Martín, et al. on page 3224.

Synthesis of (MeO)2Bn2C70: Regiochemistry of 2-fold Additions to C70 with Addends That Are Preferential for Ortho Addition and Capable of Para Addition

Three C70 tetraadducts, 2,10-(MeO)2-5,9-Bn2C70 (6), 1,56-Bn2-2,57-(MeO)2C70 (7, 2 o'clock isomer), and 1,41-Bn2-2,58-(MeO)2C70 (8, 12 o'clock isomer), were obtained from the reaction of C70 with MeO- and BnBr (benzyl bromide). The structures of 6-8 were resolved via single-crystal X-ray diffraction and spectroscopic characterizations. Computational calculations on the electrophilic Fukui functions fk+, the stability of reaction intermediates, and activation barriers for the key processes of the reaction were performed to rationalize the regioselectivity of the reaction. A conversion of the 5 and 12 o'clock intermediates to the 2 o'clock intermediate was proposed to account for the regioselectivity related to the 2-fold additions at the two distinctive polar regions of C70. Electrochemical study showed a similar electron deficiency for the 2 and 12 o'clock isomers, while the 2,5,9,10-tetraadduct was more electron deficient with respect to the 2 and 12 o'clock isomers.

Phase-transfer catalysis in the oxidation of C60 and C70 fullerene with KMnO4 and crown ether

ABSTRACTThe KMnO4 oxidation reaction of C60 or C70 fullerenes in benzene solution proceeds smoothly and almost quantitatively in presence of the crown ether 18-crown-6 as phase-transfer agent. The oxidation reaction was followed spectrophotometrically from the early stages to the completion. Essentially fullerenols or polyhydroxylated fullerenes were produced as confirmed also by FT-IR spectroscopy. The resulting degree of hydroxylation of both C60 and C70 was determined as C60(OH)28 and C70(OH)26. As secondary structures, also epoxide and carboxylic groups were detected.

The mechanochemical reaction of C60 and Bi(NO3)3·5H2O

ABSTRACTThe mechanochemical reaction of C60 and Bi(NO3)3·5H2O was performed under ball-milling condition. The product was well characterized by spectroscopic methods such as IR, Raman, UV-vis, 13C NMR, as well as elemental analysis method. The spectroscopic investigation indicates that some hydroxyl and nitro groups are attached to the C60 and no profound structural changes occur for the C60 cage in the product. The elemental analysis gives an average composition of C60(NO2)2(OH)21 for the product. A possible mechanism is suggested for the reaction.

Synthesis of Tetrahydrothiophene 1,1-Dioxides Fused to Oxazolidin-2-one and Morpholin-2-one Fragments

While developing methods of synthesis of sulfolanes fused through the C3–C4 bond to oxazolidin-2- one and morpholin-2-one fragments, the reactivity of cis- and trans-isomeric amino alcohols of the sulfolane series toward a number of cyclizing agents was studied. The cis isomers reacted with dimethyl acetylenedicarboxylate and triphosgene to afford the corresponding morpholin-2-ones and oxazolidin-2-ones, whereas the trans isomers gave rise to open-chain aminofumarates and urea derivatives, respectively. The reactions of both cis- and trans-amino alcohols with oxalic acid derivatives (diethyl oxalate, oxalyl chloride) led to the formation of exclusively acyclic mono- and/or diamides.

New Pd/Pt-[60]fullerene complexes of phosphorus ylides as anticancer agents: Cytotoxic investigation and DFT calculations

Reaction of C60 with [Pd/Pt(dba)2] (dba = dibenzylideneacetone) and phosphorus ylides [Ph2P(CH2)nPPh2 = C(H)C(O)C6H4-m-OMe] (n = 1, (Y1); n = 2, (Y2)) gave the new Pd/Pt-[60]fullerene complexes. The obtained [(η2-C60)Pd(κ2-Y1)] (1), [(η2-C60)Pt(κ2-Y1)] (2), [(η2-C60)Pd(Y2)2] (3) and [(η2-C60)Pt(Y2)2] (4) complexes were characterized successfully by cyclic voltammetry, elemental analysis, mass spectrometry, and IR, UV-Vis and multinuclear NMR (1H, 13C and 31P) spectroscopy. The results of spectroscopic characterization revealed the different coordination modes of phosphorus ylides Y1 and Y2 as a consequence of P,C-chelation in 1 and 2 and P-coordination in 3 and 4 complexes. Theoretical studies confirmed the P,C-chelation and P-coordination behaviors of ligands Y1 and Y2, respectively. The energy decomposition analysis (EDA) showed that both C60-metal and metal-ylide bonds were more electrostatic than covalent in character. Also, the cytotoxicity activity assays have demonstrated that these complexes could effectively inhibit specific cancer cells lines.

Direct benzyne-C60 addition does not generate a [5,6] open fulleroid

Recent reports describe the different products resulting from the reaction of C60 with benzyne generated from anthranilic acid derivatives and isoamyl nitrate in the presence and absence of triethylamine. Reinvestigation here via 1H, 13C, HMBC NMR and Mass spectroscopy elucidates that these products are the [6,6] closed C60-fused δ lactones, and not the [5,6] open fulleroids which would result from benzyne addition. Furthermore, theoretical calculations show that the open isomer [5,6] benzyne addition is less stable than the [5,6] closed isomer as an isolable product.

Regioselective Nucleophilic Additions to Diiron Carbonyl Complexes Containing a Bridging Aminocarbyne Ligand: A Synthetic, Crystallographic and DFT Study

Diiron µ‐aminocarbyne compounds, 1a–e, are prepared in two steps from Fe2Cp2(CO)4, negating the need for difficult purification procedures of intermediate species; they are efficiently isolated by alumina chromatography. Minor amounts of µ‐aminocarbyne aryl isocyanide compounds, 2a–c, are obtained as side products. The structures of the cations in 1a,c,e are calculated using DFT; the carbyne carbon is generally predicted to be the thermodynamic site of hydride addition, in agreement with a previous experimental finding concerning 1a. Accordingly, the reaction of 1e with NaBH4 affords a bridging aminocarbene complex, 4, in 85 % yield. Otherwise, the reaction of 1c with NaBH4 yields the aminocarbyne–cyclopentadiene derivative 3 (70 %), presumably as a consequence of the steric protection exerted by the xylyl–methyl groups towards the carbyne moiety. The sequential treatment of 1a,c with Li2CuCNMe2 and MeSO3CF3 affords 5a,b, comprising both aminocarbyne and alkoxycarbene ligands. In accordance with DFT calculations, the alkoxycarbene moiety in 5a is the most favourable site for nucleophilic attack. Thus, the reactions of 5a with NH2R (R = Et, iPr) and NBu4CN, respectively, give the aminocarbyne/aminocarbene complexes, 6a,b, and the aminocarbyne‐α‐cyanoalkyl 7. All the products are fully characterized by spectroscopic and analytical methods; moreover, the structures of 1a, 1d, 6a and 7 are elucidated by single‐crystal X‐ray diffraction studies.