The reaction of perfluoroalkanesulfonyl halides VII. Preparation and reactions of trifluoromethanesulfonyl bromide

The reaction between sodium trifluoromethanesulfinate, which was prepared from trifluoromethyl bromide, with bromine in aqueous solution resulted in the formation of trifluoromethanesulfonyl bromide (CF₂SO₂Br). CF₃SO₁Br reacted with alkenes and alkyne to give the corresponding adducts with the loss of SO₂ in good yields, and with compounds containing active hydrogen to give brominated derivatives. A radical reaction mechanism was proposed and confirmed by EPR study.     

The reaction of perfluoroalkanesulfonyl halides IX. The syntheses of bisperfluoroalkyl butadienes and perfluoroalkylated dienoates

The title compounds were prepared in good yield through the reaction of perfluoroalkyl butadiene and 2,4-dienoates with perfluoroalkanesulfonyl bromide in the presence of benzoyl peroxide followed by HBr elimination.     

PEG 400 promoted nucleophilic substitution reaction of halides into organic azides under mild conditions

Abstract

Polyethylene glycol 400 (PEG 400) has been demonstrated as an efficient and eco-friendly reaction medium for the preparation of organic azides from structurally diverse halides by nucleophilic substitution reaction with NaN₃ under mild conditions. The advantages of this protocol are: operational simplicity, environmental safety, broad substrate scope, excellent functional group tolerance, and short reaction time. The PEG 400 can be recovered and reused.     

The reaction of 1,2-dilithiotetrafluorobenzene with group V halides

Although the arsenic containing analogue of triptycene, 5,10-$\text{o}$-benzenoarsanthrene $\text{A}$ (E=As) was isolated some time ago [1] the related derivatives of antimony and bismuth are unknown. We now find that when 1,2-diiodotetrafluorobenzene is treated with methyllithium at -78/dg, to afford the little studied dilithiotetrafluorobenzene [2], and the appropriate metal chloride is added to the resulting solution, perfluorinated analogues of $\text{A}$ (E = As, Sb, or Bi) are obtained in good yield. These are stable volatile solids.

     

A general method for the preparation of perfluoroalkanesulfonyl chlorides

A mild two-step synthesis of perfluoroalkanesulfonyl chlorides starting from perfluoroalkyl iodides has been developed. Reaction of perfluoroalkyl iodides with sodium dithionite gave sodium perfluoroalkanesulfinate salts which were converted into perfluoroalkanesulfonyl chlorides in 25-73% yield (two steps) using N-chlorosuccinimide.     

A novel method for introducing a polyfluoroalkyl group into aromatic compounds

Introduction of a polyfluoroalkyl group into aromatic compounds was achieved by Friedel-Crafts reaction using (1-chloro-1-hydroperfluoroalkyl) sulfides 1, and the subsequent desulfurizing-difluorination of the resulting product using IF₅/Et₃N-nHF. Perfluoroethyl, 1,1,2,2,3,3-hexafluoropropyl, and 1,1,2,2,3,3,4,4,5,5-decafluoropentyl groups were introduced to various aromatic compounds by this method. Selective perfluoroethylation of uracil at the 5-position was also performed.     

Accurate pKa determination for a heterogeneous group of organic molecules.

Single-molecule studies that allow to compute pKa values, proton affinities (gas-phase acidity/basicity) and the electrostatic energy of solvation have been performed for a heterogeneous set of 26 organic compounds. Quantum mechanical density functional theory (DFT) using the Becke-half&half and B3LYP functionals on optimized molecular geometries have been carried out to investigate the energetics of gas-phase protonation. The electrostatic contribution to the solvation energies of protonated and deprotonated compounds were calculated by solving the Poisson equation using atomic charges generated by fitting the electrostatic potential derived from the molecular wave functions in vacuum. The combination of gas-phase and electrostatic solvation energies by means of the thermodynamic cycle enabled us to compute pKa values for the 26 compounds, which cover six distinct chemical groups (carboxylic acids, benzoic acids, phenols, imides, pyridines and imidazoles). The computational procedure for determining pKa values is accurate and transferable with a root-mean-square deviation of 0.53 and 0.57 pKa units and a maximum error of 1.0 pKa and 1.3 pKa units for Becke-half&half and B3LYP DFT functionals, respectively.     

The destruction of organic pollutants under mild reaction conditions: A review

A survey of the literature covering the destruction of organic pollutants accomplished under mild reaction conditions is presented. Technologies presented are segregated according to two main reaction pathways; oxidation and reduction. Sub-topics discussed are representative of the main component of the degradation system, including the following; electrochemical reactors, hydrogen as a reducing agent, zero-valent metals, biological based systems, photolytic processes, Fenton reaction, and a recently discovered process that is a form of room temperature and pressure oxygen activation.     

Novel method for incorporating the CHF(2) group into organic molecules using BrF(3)

2-Alkyl-1,3-dithiane derivatives, easily made from alkyl bromides and the parent 1,3-dithiane, were reacted with BrF(3) to form the corresponding 1,1-difluoromethyl alkanes (RCHF(2)) in 60-75% yield. The reaction proceeds well with primary alkyl halides. The limiting step for secondary alkyl halides is the relatively low yield of the dithiane preparation. The two sulfur atoms of the dithiane are essential for the reaction.     

A group contribution method applied to electronic correlation energies of molecules

A scheme for assigning molecular correlation energies to bonds within the molecule is proposed and applied to a variety of molecules for which nonempirical electronic energies and heats of formation are available. The bond correlation energies are employed to predict the molecular correlation energies of some molecules and good agreement was found between the predicted and “experimental” values.     

A method for determining reaction paths in large molecules: Application to myoglobin

An algorithm is described for determining reaction paths between two known structures with many degrees of freedom. The method uses first-derivative techniques to optimize the entire path between the two end forms subject to certain constraints. The stability and convergence properties of the method are illustrated by applications to structural transitions in two test systems (cyclohexane and dialanine) and to a conformational change involving all degrees of freedom in the protein, myoglobin, with 1531 atoms.     

A class of new silylating reagents. I. A mild method for introduction of the tert-butyldimethylsilyl group.

$\text{t}$-Butyldimethylsilyl enol ethers of pentane-2,4-dione and methyl acetoacetate react rapidly at room temperature to give high isolated yields of the t-butyldimethylsilyl ethers of a variety of alcohols.     

A safe and mild synthesis of organic carbonates from alkyl halides and tetrabutylammonium alkyl carbonates

A safe and mild procedure for the synthesis of mixed organic carbonates is described. Reaction of commercially available tetrabutylammonium methoxide and ethoxide with carbon dioxide yields the corresponding methyl and ethyl tetrabutylammonium carbonates (TBAMC and TBAEC). The reactions of these new compounds with several different alkyl halides give methyl and ethyl carbonates in high yields. The use of classic toxic and harmful chemicals such as phosgene and carbon monoxide is avoided.     

A new method of introducing functional substituents into the molecules of unsaturated compounds

Russian Chemical Bulletin -     

A nonlinear group contribution method for predicting the free energies of inclusion complexation of organic molecules with alpha- and beta-cyclodextrins

A group-contribution method was developed for calculating the binding constants or the free energies of complexation between native alpha- or beta-cyclodextrin (CD) and organic guest molecules. The nonlinear models for binary (1:1 stoichiometry) complexes of alpha- and beta-CDs were derived with squared correlation coefficients (r(2)) of 0.868 and 0.917 based on a database consisting of 102 and 218 diverse guest molecules, respectively. The parameters used in the models are first-order molecular connectivity index as a measure of molecular bulk and atom/group counts in the guest molecules. The models allow accurate estimations for the wide range of guests containing C, H, N, O, S, and/or all halogens by summing the contribution values of each defined group present in the chemical structure of the guest along with guest's molecular size factors (linear and square terms) and then the summation to a constant coefficient value. The predictive performance of the models was tested by extra set of 27 compounds which were not included in the original data set. The predicted values by the models are in good agreement with the experimentally determined data.     

The pyrolytic identification of organic molecules: I. The pyrolytic behavior of organic molecules

Results of a study on the pyrolysis of about 70 organic compounds of varied composition are presented and discussed. Identification of the volatile products formed was accomplished by mass spectrometry. It is shown how the pyrolytic patterns may be employed to distinguish one molecule from another. Some attention has been given to isomeric compounds and to aromatic structures containing one or more functional groups.     

Mild method for Ullmann coupling reaction of amines and aryl halides

[reaction: see text] Ullmann-type aryl amination of aryl iodides and aryl bromides in DMSO at 40-90 degrees C gave the corresponding N-arylamines or N,N-diarylamines in good to excellent yields by using either N-methylglycine or L-proline as the ligand.     

Conversion of organic halides to disulfanes using KCN and CS2

A sulfur transfer reagent was produced in situ upon stirring a mixture of KCN and CS₂ in DMF at r.t. for 15 min, which after heating with an alkyl halide or aryl halide and CuI gave the corresponding symmetric dialkyl or diaryl disulfide, respectively, in high to excellent yields.