Interaction of sodium and potassium ions withκ-carrageenan

Summary NMR and potentiometric methods revealed at least two types of interactions of Na⁺ and K⁺ ions with -carrageenan, viz., Coulombic interaction with polysaccharide sulfate groups, and a coordination one, leading, in the case of the Na⁺ ions, to formation of nonstoichiometric complexes. The absence of any correlation between the coordination binding density of the cations and their promoting effect on gelation process was demonstrated.     

A simple route to dinuclear complexes containing unusual μ-Nsulfonamido bridges

We report here the straightforward synthesis of some dimeric transition metal complexes of three Schiff base ligands, which were obtained by condensation of 2-tosylaminomethylaniline with 2,3-dihydroxybenzaldehyde (H₂L¹), 2,4-dihydroxybenzaldehyde (H₂L²), and 4-formyl-3-hydroxybenzoic acid (H₂L³), respectively. Both ligands and complexes were characterized by a combination of ¹H NMR, infrared and mass spectrometries, and elemental analyses. Furthermore, the crystal structures of H₂L² and Pd₂L²₂·2MeOH were elucidated by X-ray diffraction. The crystal structure of Pd₂L²₂·2MeOH has instead of typical μ-O_phenoxo bridges, repeating units held together by unusual μ-N_sulfonamido bridges. This complex is chiral, although it crystallizes as a racemate, with C_2v symmetry, where the two bridging nitrogens are asymmetric centers with identical handedness.     

A new efficient route for the synthesis of 4,4′,6,6′-tetra(azido) azo- 1,3,5-triazine

A new method for the synthesis of 4,4′,6,6′-tetra(azido)azo-1,3,5-triazine(TAAT)is described.The key intermediate 4,4′,6,6′- tetra(azido)hydrazo-1,3,5-triazine(TAHT)was synthesized by nucleophilic substitution in the case of sodium azide as nacleophile. N-Bromosuccinide(NBS)was used as oxidant to oxidize TAHT by a tractable operation under mild reaction condition.The target compound TAAT was obtained with a facile process and high overall yield of 81%.The structures of TAAT and its intermediates were identified by spectroscopic methods.     

Transition metal-catalyzed cross-coupling of 1,4-diiodobutadienes with thiols—A novel route to 1,4-bis(R-sulfanyl)buta-1,3-dienes

Cross-coupling of 1,4-diiodobuta-1,3-dienes with thiols in the presence of Pd, Ni, and Cu complexes gives 1,4-bis[aryl(alkyl)sulfanyl]buta-1,3-dienes in high yields.     

Regioselective amidation of allylic α-hydroxyphosphonates with Nitriles: A convenient route to (3-acetylamino-1-alkenyl)-phosphonates

Summary Reaction of dialkyl (1-hydroxy-2-alkenyl)- and (1-hydroxy-2-cycloalkenyl)phosphonates (1) with acetonitrile in the presence of trifluoromethane sulfonic acid (TfOH) affords regiospecifically and with high (E)-stereoselectivity the 1,3-transposed acetamides3 in modest to good yields.

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Regioselektive Amidierung von allylischen -Hydroxyphosphonaten mit Nitrilen: Ein einfacher Weg zu (3-Acetylamino-1-alkenyl)phosphonaten

Zusammenfassung (1-Hydroxy-2-alkenyl)- und (1-Hydroxy-2-cycloalkenyl)phosphonate (1) reagieren mit Acetonitril in Gegenwart von Trifluormethansulfonsäure (TfOH) in mäßigen bis guten Ausbeuten regiospezifisch und mit hoher (E)-Stereoselektivität zu den 1,3-umgelagerten Acetamiden3.

     

Redoping — A simple way to enhance the redoxcapacity of polypyrrole films

In this work, the beneficial structural properties of polypyrrole (PPy) films formed in the presence of benzenesulfonate (BS) and para-toluenesulfonate (pTS) were combined with the good mobility of small inorganic anions as chloride by redoping (ion exchange). the combination of voltammetry as the classical method for the determination of redoxcapacity together with the analytical determination of the doping level before and after redoping by X-ray microanalysis (EDS) allow to optimize the redoping process and produce PPy films with high redoxcapacity and stability.     

Cross metathesis of β-carotene with electron-deficient dienes. A direct route to retinoids

Cross metathesis (CM) reactions of β-carotene and alkenes occur regioselectively in the presence of the Hoveyda second generation catalyst. Scission of the C15-C15′ and C11-C12 bonds of β-carotene in all CM reactions predominates. The reaction with ethyl (2E,4E/Z)-3-methylhexa-2,4-dienoate is both regio- and diastereoselective, and affords ethyl all-trans-retinoate as the major product, if suitable CM conditions are applied.     

Reaction of α-(trialkylstannyl) acetylenes with metallic sodium

-Trialkylstannylacetylenes react under mild conditions with metallic sodium at the Sn-C(sp) bond to give hexaalkyldistannanes and sodium acetylalkynides inca. 65–85 % yields.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1109–1110, June, 1994.     

The Interaction of Arsenazo III with Nd(III)—A Chemometric and Metrological Analysis

Interactions of Arsenazo III with Nd(III) in aqueous solutions (pH range 3 to 4) were studied using a spectrophotometric method. Some discrepancies are present in literature concerning the concentrations of the prevailing species and their composition. Threshold bootstrap computer-assisted target factor analysis (TB CAT) was applied to the evaluation of UV-VIS spectra of Arsenazo III in aqueous solutions containing varying amounts of neodymium(III) ions. The thus obtained experimental data are interpreted with consideration of the measurement uncertainties affecting this system. Within the limits of resolution of the experimental method, two complexes NdAazo and Nd(Aazo)₂ were indicated in the studied pH range. The values of formation constants for log ₁₀ β ₁₁ fall in the range 4.9 to 6.3 and for log ₁₀ β ₁₂ fall between 10.5 and 12.1.     

A new route to the zizaane sesquiterpenes: An efficient synthesis of (±)-isokhusimone

A novel route to the zizaane sesquiterpene skeleton is demonstrated with a nine-step synthesis of (±)-isokhusimone (2) from norcamphor in an overall yield of 35%. This constitutes a formal synthesis of (±)khusimone (1).     

Reaction of γ-(aminopropyl)siloxanes with phenolphthalein as a route to new siloxane-containing phenols

The reaction of γ-aminopropylorganosiloxanes with phenolphthalein yields monomeric and oligomeric N-alkylsiloxy-3,3-bis(4-hydroxyphenyl)phthalimidines. Their structures and compositions were confirmed by IR and NMR spectroscopy and by HPLC-MS. Studies by GLC and MALDI mass spectrometry showed that the action of the amine and of the water released in the reaction leads to the rearrangement of the siloxane bond in the course of the synthesis with the formation of linear and cyclic carbofunctional oligomeric siloxanephenols and mixed oligophenolaminosiloxanes. The possibility of modification of epoxy resins with the synthesized oligomers was revealed.     

A new modification of the Friedländer synthesis. A simple route to 2-aminoquinoline-3-carboxylic acid and its derivatives

A new version of the Friedländer synthesis of 2-aminoquinoline-3-carboxylic acid and its derivatives from stable 2-tosylaminobenzaldehyde or its morpholinal was proposed.     

Unusual oxidative cleavage of the aryl—ethynyl bondsin (arylethynyl)polymethylbenzenes with iodine in dimethyl sulfoxide

While heating 1,2,4,5-tetramethyl-3,6-bis(phenylethynyl)benzene, 1,3,5-trimethyl-2,4-bis(phenylethynyl)benzene, and 1,2,4,5-tetramethyl-3-(phenylethynyl)benzene with iodine in DMSO in the absence of oxygen, the triple bonds are oxidized to give the corresponding 1,2-diketones. In the presence of oxygen, the previously unknown competitive oxidative process causes the cleavage of the aryl—ethynyl bonds so that duroquinone and the corresponding 4-hydroxybenzils are formed. This cleavage is produced by oxygen only in the presence of iodine and DMSO. It was shown that the key stage of the process is the formation of intermediate charge-transfer complexes between polymethylbenzene rings and iodine.     

A simple synthetic approach to unsymmetrically substituted (γ-oxoalkyl)phosphine oxides

Russian Journal of Organic Chemistry -     

A simple new general synthesis of macrocyclic ketones: A new entry to the synthesis of exaltone and (±)-muscone

We describe an efficient new synthesis of 15-membered cyclic ketones, exaltone and (±)-muscone, based on a three-carbon annelation of cyclic ketones followed by the regioselective radical cleavage of the fused bond of the resulting bicyclic systems.     

A simple one-pot procedure for the iminium salt formation: an efficient route to β-arylethylamines

A practical and highly efficient process for the preparation of β-arylethylamines 7 was developed. Benzylic organozinc compounds 10 were reacted with the iminium salts 9 generated in situ from the amine salt 8 and paraformaldehyde in one pot and in a polar and aprotic solvent, such as NMP. A variety of the β-arylethylamines were prepared in 43-91% yields.     

A di-μ-oxomolybdenum(V) complex of 6-acetonylisoxanthopterin,undergoing oxygen atom transfer with dimethyl sulphoxide

The new compound, Na[(Mo₂ ^VO₄)(pte)(OMe)(MeOH)₂] (pte = anion of 6-acetonylisoxanthopterin), has been prepared using the redox non-innocent title ligand in MeOH–H₂O, and characterized by elemental analysis and physico-chemical methods including e.s.m.s., i.r., u.v.–vis. and ¹H-n.m.r. spectra. Rate constants data (1.4 × 10^–3 s^–1 at 300 K) for its oxygen atom transfer with dimethyl sulphoxide tally with those of synthetic analogue systems reported earlier by different authors. The negative activation entropy (–206.3 J mol^–1 deg^–1) is consistent with an associative mechanism for this reaction.