Sensory monitoring of the native state of natural waters

A procedure has been proposed for express assessment of the degree of pollution of melt and snow waters with volatile aromatic compounds using a set of chemical sensors. The number of measuring units has been minimized to 2 for the yes/no detection (alarm system) of volatile aromatic toxicants in natural waters of different salinities. An algorithm has been developed for the extraction of analytical information on the presence of volatile compounds or salts in meltwater by the sorption efficiency parameters A _ij and their profiles (petal diagrams) or by cluster analysis.     

Recyclable synthesis of mesityl iodonium(III) salts

An efficient protocol for C–H condensation of hypervalent iodine compounds toward arenes in fluoroalcohols has been applied to the recyclable preparation of mesityl iodonium(III) salts. The electrophilicities of [hydroxy(tosyloxy)iodo]mesitylene (MesI(OH)OTs) and iodomesitylene diacetate (MesI(OAc)₂) are suitably enhanced in 2,2,2-trifluoroethanol. A series of nucleophilic aromatic compounds react smoothly with MesI(OH)OTs and MesI(OAc)₂ or in situ hypervalent iodine(III) species, generated from iodomesitylene, to provide the target mesityl iodonium(III) salts in good yields at room temperature with broad functional group tolerance. This C–H condensation strategy merits high para-regioselectivities during the diaryliodonium(III) salt formation, but the major limitation in the case of low-reactive aromatic substrates is byproduct formation resulting from the self-condensation of the nucleophilic mesitylene ring in MesI(OH)OTs and MesI(OAc)₂.     

Cyclization of secondary aromatic amines with formaldehyde and cyclopentanone

Secondary aliphatic-aromatic and aromatic amines react with formaldehyde and cyclopentanone in the presence of perchloric acid to form cyclopenta[c]quinolinium salts in good yields. The yields of the cyclization conditions as a function of reagent ratio and reaction time and temperature were studied, and procedures for isolation and purification of the target compounds were developed.     

An efficient catalytic ylide route to vinyl epoxides

The ylide epoxidation catalyzed by telluronium salts provides a simple and extremely efficient route to vinyl epoxides in excellent yields. Both aromatic and aliphatic aldehydes work well. The best results were obtained by using 2 mol% of telluronium salts with Cs₂CO₃ in t-BuOH.     

Highly efficient synthesis of spirocyclic (1R)-camphor-derived triazolium salts: application in the catalytic asymmetric benzoin condensation

New (1R)-camphor-derived triazolium salts, incorporating a spirocyclic system, are described. Benzoin condensation of aromatic aldehydes, mediated by these salts affords α-hydroxyketones in good yields and moderate enantiomeric excesses.     

Analysis of the 13C-n.m.r. spectra of mono- and dimethylamphetamines

The ¹³C-n.m.r. spectra of the three monomethylainphetainines and the six dimethyl-amphetanunes and their hydrochlorides were determined. Spectra were distinctive and suitable for identification and authentication purposes. Signals were assigned by a self-consistent analysis of chemical shift differences between differently-substituted compounds in the series of both the bases and the salts. Determination of the effects of N-protonation on the chemical shifts of aromatic ¹³C signals was a valuable aid in resolving some ambiguities: C-1 shifted upfield by about 0.9 ppm, and methylated carbons ortho, meta, and para to the isopropylamine side-chain shifted downfield by about 3.3, 3.7, and 4.4 ppm, respectively. The data are useful in the authentication of reference materials employed in forensic analysis.     

Enantiomerically pure α-pinene derivatives from material of 65% enantiomeric purity. Part 2: C2-symmetric N,N′-3-(2α-hydroxy)pinane diimines and diamines

The conversion of enantiomerically enriched (ee >99%) 2α-hydroxypinan-3-one and its oxime (obtained in previously described procedures¹ from α-pinene of 65% ee) into a range of derivatives with potential application in asymmetric synthesis was attempted. C₂-Symmetrical compounds, ligands for potential catalysts, were synthesized from 2α-hydroxypinan-3-one and either aliphatic or aromatic diamines. Reduction or etherification/reduction of selected diiminodiols afforded respective diaminodiols and diaminoethers, which were further transformed into azolium salts. Reactions of dipinanediaminoethers with dichlorophenylphosphine and subsequent in situ oxidation of the products afford the respective stable phosphinediamide oxides. Four selected compounds were crystallographically studied.     

Direct arylation of tertiary amines via aryne intermediates using diaryliodonium salts

With a strategy by using diaryliodonium salts as the precursors of benzynes, direct N-arylation of tertiary amines with diaryliodonium salts was reported. Thus, the desired aromatic tertiary amines with a wide range of substituents were synthesized in moderate to excellent yields of 55–91%.     

Chromatographic behaviour of aromatic compounds on gel filtration Media

Summary Highly cross-linked gels utilized as gel filtration media exhibit adsorption effects towards aromatic or apolar compounds. The adsorption is linearly dependent on salt concentration. We investigated the effect of various salts spanning the Hofmeister series on the adsorption of three model compounds, Adenosine 5′-phosphate, ε-dinitrophenyllysine and tryptophan. It was found that salts exhibiting marked salting-out properties, such as potassium phosphate and sodium sulfate, were the most effective in enhancing the adsorption were the most effective in enhancing the adsorption of the aromatic molecules onto the gel. On the contrary, in the presence of salts with marked salting-in properties, such as Kl or KSCN, the linear dependence of elution parameters for the same compounds was negatively correlated and adsorption decreased with salt concentration. However, a number of salts of intermediate character in the Hofmeister series, such as NaCl or NH₄Cl, did not affect the elution behaviour of the chosen model compounds. The different effects observed are probably due to differential hydration of the molecules in the presence of the salts and to the consequent different hydrodynamic behaviour of the solute when interacting with the hydration layers of the gel matrix.     

First report of syn isomers in the diastereoselective synthesis of highly functionalized piperidines catalysed by wet picric acid: factors influencing the syn-anti ratios

This is the first report of the formation of a syn-diastereoisomer in the diastereoselective synthesis of highly functionalized piperidines catalysed by wet picric acid via a one-pot, step-economic condensation of aromatic aldehydes, 1,3-dicarbonyl compounds and aromatic amines. DFT calculation shows that anti isomers are more stable compared to the syn. The syn-anti ratio of the products depends on the temperature and the nature of substitution on both the aromatic aldehydes and aromatic amines. Conditions for getting pure anti and pure syn compounds have been studied.     

Isobenzopyryliumsalts: VII—13C n.m.r. shifts of 1-arylisobenzopyrylium salts and correlation with Hammett parameters

The signal identifications of isobenzopyrylium salts has been achieved on the basis of proton broad-band and off-resonance decoupled ¹³C n.m.r. spectra of twelve different 1-arylisobenzopyrylium salts and eight model compounds. From the ¹³C shifts valuable information about pK values, the aromatic character and the conjugative effects of isobenzopyrylium salts was obtained.     

Potentiometric determination of tetraphenylborate with silver nitrate

A simple potentiometric method for determining the tctraphenylborate ion (C₆H₅)₄B- contents of organic amine tetraphcnylborate salts has been developed. The compounds arc dissolved in 1 : 1 aqueous acetone; and the solution is buffered at a pH of 5 with 3M acetic acid and 3M sodium acetate. The resulting solution is then titrated with 0.06N aqueous silver nitrate, using a silver indicating electrode, a glass reference electrode and a Beckman pH meter to indicate EMF changes. Platinum electrodes in conjunction with the Malmstadt automatic titrator can also be used. Good end-points were obtained for all structure types except the primary aromatic amine borates. Values for (C₆H₅)₄B- found were within 2% of theory for 22 compounds so analyzed.     

Neue Reineckesalzanaloge Verbindungen mit tertiären aromatischen Aminen

Substitution reactions of anhydrous K₃[Cr(NCS)₆] with tertiary aromatic monoamines such as N,N-dimethylaniline and N,N-diethylaniline were carried out in the absence of solvents. The tertiary amines readily form compounds analogous to Reinecke salts,amine ₂H[Cr(NCS)₄(N,N-dimethylaniline)₂] andamine ₂H[Cr(NCS)₄(N,N-Diethylaniline)₂] respectively. The formula of the new complex anions was established by a series of double decomposition reactions with the hydrochlorides of some heterocyclic N-bases, alcaloids and cobalt(III)-ammine complexes. Some structural problems were resolved by UV and IR spectroscopic studies.     

A practical variation on the Leuckart reaction

S-Aryldiazo xanthates, derived from the corresponding diazonium salts by reaction with potassium O-ethyl xanthate, undergo a radical chain reaction with loss of nitrogen; the intermediate aromatic radical can be captured by an internal olefin to give bicyclic xanthates in good overall yield.     

Introduction of the pyrylium ring into compounds of the aromatic and heterocyclic series

Halogen-substituted pyrylium cations react with organic nucleophilic compounds via an electrophilic mechanism to form new pyrylium salts. The reaction is extended to aromatic, heterocyclic, andnonbenzoid aromatic systems. Pyrylium salts that contain other functional groups do not enter into this reaction. The IR spectra of the compounds obtained are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1320–1323, October, 1971.     

New and highly efficient synthesis of 3-substituted 1-hydroxybenz[g]isoquinoline-5,10-diones

A new and efficient strategy for the synthesis of 3-substituted 1-hydroxybenz[g]isoquinoline-5,10-diones by reaction of 2-methoxycarbonyl-1,4-naphthoquinone with different pyridinium salts under Kröhnke conditions is disclosed. This one-step reaction was found to be dependent on the substitution pattern of the aromatic nucleus in the pyridinium salts.     

Enantioseparation of protonated primary arylalkylamines and amino acids containing an aromatic moiety on a pyridino-crown ether based new chiral stationary phase

This paper reports the preparation and testing of a new pyridino-18-crown-6 ether based chiral stationary phase (CSP). The chiral crown ether was covalently bound to silica gel. Circular dichroism (CD) spectroscopy was used for probing the complex formation of the chiral crown ether with the enantiomers of protonated primary arylalkylamines. The (S,S)-dimethylpyridino-18-crown-6 ether selector having a terminal double bond was first transformed to a triethoxysilyl derivative by regioselective hydrosilylation, and then heated with spherical HPLC quality silica gel to obtain the CSP. The discriminating power of the HPLC column filled with the above CSP was tested by using the hydrogenperchlorate salts of racemic α-(1-naphthyl)ethylamine (1-NEA), α-(2-naphthyl)ethylamine (2-NEA) and the hydrochloride salts of aromatic α-amino acids and α-amino acids containing different aromatic side-chain protecting groups.     

Viologen derivatives with extended π-conjugation structures: From supra-/molecular building blocks to organic porous materials

Recently, increasing attention has been paid on extending the π-conjugation structures of viologens (1,1′-disubstituted-4,4′-bipyridylium salts) by incorporating planar aromatic units into the bipyridinium backbones. Various viologen derivatives with extended π-conjugation structures have been synthesized, including the N-termini aromatic substituted viologens, the extended π-conjugated viologens (denoted as ECVs) as well as the π-conjugated oligomeric viologens (denoted as COVs). These compounds typically exhibit interesting properties distinguished from those of an isolated viologen unit, which make them as new class of electron deficient supra-/molecular building blocks in supramolecular chemistry and materials science. In this review, we would like to highlight the recent advances of viologen derivatives with extended π-conjugation structures in versatile applications ranging from electrochromic and energy storage materials, the ECV/COV-based supramolecular self-assembly systems including the linear supramolecular polymers and 2D/3D supramolecular organic frameworks (SOFs), to the viologen-based covalent organic frameworks (COFs)/networks. We hope this review will serve as an in-time summary worthy of referring, more importantly, to provide inspiration in the rational design of novel molecules with unexplored properties and functions.     

2-Styryl-4H-1,3-benzoxazin-4-onium salts

A method was developed for the synthesis of 2-styryl-4H-1,3-benzoxazin-4-onium salts by condensation of 2-alkylbenzoxazinonium salts with aromatic aldehydes. It is shown that these same compounds are formed by acid condensation of salicylamides, salicylnitrile, or salicylaldoxime with aromatic aldehydes in acetic anhydride. The hydrolysis and alcoholysis of the synthesized salts were studied.     

Tris(1-alkylindol-3-yl)methylium salts as a novel class of antitumor agents

Tris(1-alkylindol-3-yl)methanes were obtained and oxidized into tris(1-alkylindol-3-yl)methylium salts. The resulting salts are more toxic to cultured tumor cells than to non-tumor ones. The cytotoxicity of tris(1-alkylindol-3-yl)methylium salts depends on the length of the substituent at the N atom of the heterocycle, increasing from an N-unsubstituted derivative toward N-butyl- and N-pentyl derivatives. A further increase in the length of the N-alkyl substituent lowers the cytotoxicity. The cytotoxicity of tris(1-alkylindol-3-yl)methylium salts for tumor cells correlates with their antibacterial and antifungal activity. Tris(1-alkylindol-3-yl)methylium salts produced a cytocide effect on Gram-positive microorganisms and the most active compounds, on Gram-negative microorganisms as well. Similar patterns of the structure—activity relationship of N-alkylated tris(indol-3-yl)methylium derivatives, which was observed for various lines of tumor cells, bacteria, and fungi, suggest the general character of the mechanisms of the death of prokaryotic and eukaryotic cells induced by these compounds.