Reaction Of Oxiranes Research Articles

SELENOLANES, SELENATRANS AND ESTERS OF SELENIC ACID

It is known that selenic acid and selenium dioxide act as oxidizing agents in reactions with α-oxides when heated. The proposed paper presents data on the synthesis of organoselenium compounds based on reactions of α-oxides with selenic acid and its anhydride, where the latter act as selenation agents. It was found that in the presence of catalytic amounts of boron trifluoride esterate in the reactions of oxiranes with acid the oxirane ring opens both according to the rule and against the Krasussky rule with the formation of a mixture of α- and β- isomers of selenic acid esters. In contrast to the acid, the reactions of oxiranes with selendioxide involve the expansion of the oxirane ring to form functionally substituted selenolanes. This paper is followed by the analysis of the literature material on atranes, a unique class of heterocyclic compounds with distinct biologically active properties, and their element derivatives (B, Ge, Si, etc.). For the first time we have synthesized selenatranol, which is not described in the literature. In future it may not only possess bioactive properties in itself, like the majority of organoselenium compounds, but also be a drug precursor. Acetylselenatranol was synthesized by the reaction of selenatranol with acetic anhydride in acid medium. The data of IR, PMR spectra and elemental analysis of the synthesized compounds as well as the data of thermogravimetric (TGA) and differential thermal analysis (DTA) of some of them are given

Reaction of Oxiranes with Ethyl 3-Phenyl-1H-pyrazole-5-carboxylate

Reaction of Oxiranes with Ethyl 3-Phenyl-1H-pyrazole-5-carboxylate

A facile reaction to access novel structural sulfonyl-hybridized imidazolyl ethanols as potential DNA-targeting antibacterial agents

A novel type of sulfonyl-hybridized imidazolyl ethanols as potential DNA-targeting antibacterial agents was constructed via the unique ring-opened reaction of oxiranes by imidazoles for the first time. Some developed target hybrids showed potential antimicrobial potency against the tested microbes. Especially, imidazole derivative 5f could strongly suppressed the growth of MRSA (MIC = 4 μg/mL), which was 2-fold and 16-fold more potent than the positive control sulfathiazole and norfloxacin. This compound exhibited quite low propensity to induce bacterial resistance. Antibacterial mechanism exploration indicated that compound 5f could embed in MRSA DNA to form steady 5f-DNA complex, which possibly hinder DNA replication to exert antimicrobial behavior. Molecular docking showed that molecule 5f could bind with dihydrofolate synthetase through hydrogen bonds. These results implied that imidazole derivative 5f could be served as a promising molecule for the exploration of novel antibacterial candidates.

Highly Diastereoselective Construction of Carbon- Heteroatom Quaternary Stereogenic Centers in the Synthesis of Analogs of Bioactive Compounds: From Monofluorinated Epoxyalkylphosphonates to α-Fluoro-, β-, or γ-Amino Alcohol Derivatives of Alkylphosphonates.

The synthesis of the stable surrogates of an important amino acid (R)-4-amino-3-hydroxybutyric acid (GABOB) such as substituted hydroxy aminophosphonic acids bearing a quaternary stereogenic center is presented. Highly diastereoselective formations of fluorinated spiroepoxy alkylphosphonate or related tertiary carbon-containing oxiranes from β-keto phosphonates possessing methyl, phenyl, or cyclohexenyl substituents, are reported. Stereoselective acid-promoted epoxide opening by bromide or azide followed by reduction/protection afforded tertiary bromides or N-Boc derivatives of β-amino-γ-hydroxy alkylphosphonates in most cases, while the reactions of oxiranes with different amines yielded their β-hydroxy-γ-amino regioisomers. Surprisingly, during the synthesis of amino phosphonic acids, we observe that the acid-induced rearrangement proceeded in a high diastereospecific manner, leading finally to substituted β-hydroxy-γ-aminoalkylphosphonic acids.

Photochemical ring-opening reactions of oxirane with the Ehrenfest force topology

Ehrenfest Force F(r) trajectories were constructed for the C-O ring-opening photo-reactions of oxirane. The F(r) trajectories were constructed in an eigenvector-space corresponding to bond-flexing, bond-twist and bond-anharmonicity associated with the least and most preferred directions of charge density accumulation and bond critical point (BCP) sliding respectively. The presence of the torsion of a CH2 group for one of the photo-reactions led to greater symmetry breaking and greater reaction pathway preference. Consistency was found from hybrid Ehrenfest Force F(r) trajectories that were constructed using the Ehrenfest Force F(r) BCPs and the stress tensor eigenvectors.

Synthesis of a potential bendamustine deschloro dimer impurity

Bendamustine deschloro dimer was considered as a potential impurity in bendamustine hydrochloride resulting from the hydrolysis of bendamustine followed by intermolecular esterification. An efficient synthesis of bendamustine deschloro dimer was achieved from 4-(5-amino-1-methyl-1H-benzo[d]imidazol-2-yl)butanoate involving nine sequential steps including benzyl-protection/deprotection of the amine and carboxylic acid groups, saponification, ring-opening reaction of oxirane as well as Fischer/Steglish esterfication and so on. The target bendamustine deschloro dimer was obtained using a high-performance liquid chromatography in a purity of 95.63%.

Synthesis of homo-propargylic ethers: A domino ring opening/coupling reaction of oxiranes with terminal alkynes and aryl iodides

A domino ring opening/cross-coupling reaction of oxiranes with terminal alkynes and aryl iodides has been developed. This transformation serves as a protocol for the synthesis of homo-alkyne ether skeletons from the readily available starting materials. The success of the reaction has dependence on catalyst/ligand system of choice. The synthesis utility of the alkyne ether skeletons in formation of chromane skeleton has also been studied.

Reaction of oxiranes with cyclodextrins under high-energy ball-milling conditions.

This work presents a proof of concept for a green cyclodextrin derivatisation method that uses low-boiling epoxide reagents in a high-energy ball mill (HEBM). The simplified preparation and purification of low substitution-degree common (2-hydroxy)propylated β- and γ-cyclodextrins (β/γ-CDs) has been realised. The intelligent use of propylene oxide has also facilitated the more effective synthesis of highly substituted γ-CD. Epichlorohydrin-crosslinked CD-polymers (CDPs) have also been effectively prepared in the ball mill. The unoptimised preparations of soluble and insoluble CDPs displayed very small particle size distributions, while the prepared polymers currently have different complexation properties to those of their classically prepared analogues.

Next‐generation quantum theory of atoms in molecules for the photochemical ring‐opening reactions of oxirane

AbstractThe conical intersections corresponding to the C─O and C─C ring opening were optimized and the reaction paths traversing these intersections were obtained. Investigation of the C─O ring opening revealed that when traversing the lowest energy conical intersection, the reaction path returns to the closed ring geometry. The C─O path traversing the intersection featuring torsion of terminal CH2 group however, led to a ring‐opened geometry, an H‐shift and the formation of acetaldehyde that can undergo further dissociation. The observation of different reaction paths was explained by the 3‐D paths from quantum theory of atoms in molecules (QTAIM) that defined the most preferred direction of electronic motion that precisely tracked the mechanisms of bond breaking and formation throughout the photo‐reactions. The size, orientation, and location of these most preferred 3‐D paths indicated the extent and direction of motion of atoms, bonds, and the degree of torsion or planarity of a bond indicating a predictive ability.

Synthesis of Cyclic Carbonates from Olefin Oxides and Carbon Dioxide. Communication 2. Catalysis by Metal Porphyrin Complexes

The catalytic systems based on metal porphyrin complexes used for promoting the reactions of olefin oxides with carbon dioxide were reviewed. The metal porphyrin complexes were shown to be effective catalysts for carboxylation of epoxides. The catalyzed reactions of oxiranes with carbon dioxide in the presence of homogeneous and heterogeneous metal porphyrin complexes, including the reactions with the use of various promoting additives, were considered.

Experimental and theoretical study on the kinetics and mechanism of the amine-catalyzed reaction of oxiranes with carboxylic acids

In this work, a systematic study on the kinetics and mechanism of ring-opening reaction of oxirane by carboxylic acid initiated by a tertiary amine is presented. Kinetic parameters of β-hydroxypropyl ester formation including reaction orders, rate constants, and activation energies were established at the temperature range 323–353 K. The experimental values of Δ≠H° and Δ≠S° are characteristic for the SN2-like processes. In the initial reaction system, the acid, oxirane and amine exist mainly as hydrogen-bonded complex acid-oxirane, free oxirane and free base. H-bonding was analyzed using IR-spectroscopy. The reaction pathways were examined by the density functional theory (DFT) method at the B3LYP/6-31+G** level. Optimized equilibrium configurations of transition states and corresponding activation parameters were established. In accordance to both experimental and theoretical approaches, it is reasonable to suggest that amine-catalyzed ring-opening reaction of oxirane by carboxylic acid is a series of parallel consecutive stages: (1) quaternization of tertiary amine by activated oxirane; (2) carboxylate anion participation in ring-opening of both nonactivated and activated oxirane. The kinetic model, which adequately describing all observations, is proposed.

Far-Infrared Synchrotron Spectroscopy and Quantum Chemical Calculations of the Potentially Important Interstellar Molecule, 2-Chloroethanol.

The high brightness of the Australian synchrotron allowed for detailed spectra to be collected at high resolution (0.00096 cm-1) in the vicinity of the a/ b/ c-type ν19 band of 2-chloroethanol, which involves O-H torsional motion about the C-O bond. A rovibrational analysis was performed for both chlorine isotopologues in the ν19 fundamental (centered at ∼344 cm-1) which involved the assignment of 7153 lines ( J ≤ 90, K a ≤ 41). A global fit to these lines in addition to 119 microwave lines ( J ≤ 29, K a ≤ 11) led to the determination of spectroscopic constants up to the sextic level in both the ground and excited states using Watson's A-reduction Hamiltonian. The constants agree well with those calculated at the anharmonic MP2/cc-pVTZ level and allow for spectroscopically accurate predictions of rotational transitions in the ground vibrational state to be made over a broad range of rotational energies ( TR < 1000 K). We explored the role that 2-chloroethanol might play in interstellar molecular clouds by performing calculations on the substitution reaction between HCl and ethylene glycol, and the addition reaction between HCl and oxirane, all of which have been observed in Sagittarius B2(N) and are expected to play important roles in the chemistry that occurs on the icy mantles of interstellar dust grains. While both reactions have relatively high activation barriers, the HCl + oxirane reaction was found be much more exothermic; further calculations on it indicate that a water-like environment significantly reduces the barrier while slightly increasing its exothermicity. These results suggest that 2-chloroethanol could be efficiently produced from the cosmic ray bombardment of common interstellar ices.

A Computational Study of 2-(chloromethyl)oxirane Ring Opening by Bromide and Acetate Anions Considering Electrophilic Activation with Cations of Alkali Metals

Ring opening of 2-(chloromethyl)oxirane via the nucleophilic substitution with bromide and acetate anions was investigated using density functional theory (DFT) calculations. It was shown that the geometry of the transition states and the activation parameters of the reactions correspond to those of SN2-like mechanism. The nature of localized transition states was analyzed using More O’Ferrall – Jencks plots. The quantum chemical simulations of the potential energy surface for the ring-opening reaction of oxirane by nucleophiles confirmed the theoretical assumptions about the favored path of interactions, which is a backside α-attack of nucleophile. The effect of alkali metal cation (Li+, Na+, K+) on that path was estimated. It was found that the electrophilic activation with alkali metal cation is more pronounced in the reaction of 2-(chloromethyl)oxirane with dissociated ions, than with ionic pairs.

Design of Betaine Functional Catalyst for Efficient Copolymerization of Oxirane and CO2

A new Co(III) salen betaine functional catalyst is reported which displays high activity and high selectivity for the copolymerization reaction of oxirane and carbon dioxide. Importantly, this catalyst system is not only effective for propylene oxide and CO2 but also efficient for more difficult epoxides to selectively provide copolymers. For example, styrene oxide and 2-vinyloxirane are readily coupled with CO2 to provide the corresponding completely alternating copolymers. This catalyst system is thereby able in several instances to avoid the use of tediously prepared bifunctional Co(III) salen catalysts. Through a combination of control experiments, MALDI-TOF measurements, and DFT computations, the addition of a cocatalyst is shown to play a significant role in this process.

Cross effects of structure and temperature in the reactions of trans-2,3-diaryloxiranes with arenesulfonic acids

Cross effects of the reagent structure and the temperature on the rate and activation parameters of the reactions of symmetrically X-substituted trans-2,3-diaryloxiranes with Y-substituted arene-sulfonic acids have been investigated in the temperature range 265–298 K. The isokinetic temperature of 265 K was reached, at which the rate and the free energy of the ring-opening reaction of trans-2,3-bis(3-bromo-5-nitrophenyl)-oxirane practically do not depend on substituent Y. The transition through the isoparametric points on substituent Y was realized with the inversion of the temperature effect on the free energy of activation for the reactions of oxiranes with X = 4-NO2 and 3-Br-5-NO2.

An easy one-step procedure for the synthesis of novel β-functionalised tellurides

Novel β-hydroxy-,β-amino- and β-mercapto- dialkyl- and phenyl-alkyl tellurides have been achieved through regioselective ring opening reactions of oxiranes, aziridines and thiiranes with different Te-nucleophiles, including tellurosilanes. Tellurium-125 NMR chemical shifts of selected compounds have been measured.

Nucleophile-electrophile interactions in the reaction of oxiranes with carboxylic acids in the presence of tertiary amines

The nucleophile-electrophile interactions in the reaction system “N,N-dimethylaniline – acetic acid – epichlorohydrin” have been investigated using kinetic methods and computer modeling. The observed orders of reactions have been determined for the overall reaction as well as for individual stages. The kinetic equations have been proposed; the activation parameters of the reactions have been evaluated. The behavior of the initial (amine) and intermediate (carboxylate) nucleophiles has been detailed in reaction pathway. Amine reacts with oxirane activated by acidic reagent while carboxylate-anion—with both activated and nonactivated epichlorohydrin. The mechanism of oxirane ring opening by acid reagent in the presence of tertiary amine has been proposed, which comprise parallel-consecutive compensation stages of reaction product formation. It has been demonstrated that the observed reaction order with respect to acid reactant depends upon the nature of electrophilic reagent (activated/nonactivated oxirane) and the ratio of the rates of compensation stages.

Rhenium complex-catalyzed Meinwald rearrangement reactions of oxiranes

The Meinwald rearrangement reaction of oxiranes to the corresponding carbonyl compounds is efficiently catalyzed by the ReBr(CO)5 complex.

Are amines basic or nucleophilic catalysts for oxirane ring opening by proton-donating nucleophiles?

The behavior of amines as catalysts for oxirane acidolysis and phenolysis has been studied using kinetic methods. The apparent catalytic and noncatalytic reaction rate constants have been estimated. It has been demonstrated that the noncatalytic pathway has almost no effect on the apparent reaction rate constant. In order to determine the character of the behavior of amines (bases/nucleophiles) in this reaction, their reactivity has been analyzed within the conceptions of basic and nucleophilic mechanisms of catalysis. Based on the quantitative amine structure—catalytic activity correlation, it has been shown by comparing the values of correlation coefficients (r) of equations describing mechanisms for various reaction systems that, in the reactions of oxiranes with proton donors (carboxylic acids and phenols), the catalytic activity of tertiary amines/pyridines is determined by their nucleophilicity rather than basicity.

ChemInform Abstract: Synthesis of 3‐Oxazolines via SnCl4‐Promoted Formal [3 + 2] Cycloaddition of Donor—Acceptor Oxiranes and Nitriles.

Abstract22 Title compounds (III) are prepared by the reaction of oxiranes (I) with nitriles (II).