2,6-Dithiodecahydro-1H,5H-Diimidazo[4,5,-b:4′,5′-e]Pyrazine and related dioxo- and diimino-decahydrodiimidazopyrazines

Thiourea condensed with 1,4-diformyl-2,3,5,6-tetrahydroxypiperazine 2 in the presence of hydrochloric acid to give 2,6-dithiodecahydro-1 H,5H-diimidazo[4,5,-b:4′,5′-e]pyrazine 5 isolated as the dihydrochloride salt. The salt 5 . 2HCl was converted to the free base 5 by lithium hydroxide, to the dinitrate salt 5 . 2HNO₃ by silver nitrate, degraded to 2-thio-2,3,4,7-tetrahydro-1 H-imidazo[4,5-b]pyrazine 6 in a reaction with tert-butyl amine, and converted to 4,8-dihydro-4,8-dinitro-1H,5H-diimidazo[4,5-b:4′,5′-e]pyrazine-2,6- disulfonic acid 9 by nitric acid (100%) at −40°C. Denitration of the dinitramine 9 to give 4,8-dihydro-1H,5H-diimidazo[4,5-b:4′,5′-e]pyrazine 11 was brought about by methanolic hydrogen chloride in ether. In one run nitration without oxidation converted the salt 5 · 2HCl to the dinitrate salt of the 4,8-dinitro derivative 10 ; treatment with triethyl amine liberated the free base 10 from the salt. Degradation of 2,6-dioxo-1,3,4,5,7,8-hexanitrodecahydro-1H,5H-diimidazo[4,5-b:4′,5′-e]pyrazine 12 to 2-oxo-2,3-dihydro-1,3-dinitro-1H-imidazo[4,5-b] pyrazine 13 was brought about by hydrochloric acid. Treatment with lithium hydroxide also liberated 2,6-dioxodecahydro-1H,5H-diimidazo [4,5-b:4′,5′-e]pyrazine 3 from its dihydrochloride salt. Attempts to liberate 2,6-diiminodecahydro-1H, 5H-diimidazo[4,5-b:4′,5′-e]pyrazine 4 from its tetrahydrochloride salt led instead to intractable mixtures. The tetrahydrochloride salt 4 · 4HCl was converted to the dihydrochloride salt 4 · 2HCl in a reaction with tert-butyl amine.     

Amphiphilic maleic acid-containing alternating copolymers—2. Dilute solution characterization by light scattering,intrinsic viscosity,and PGSE NMR spectroscopy

The dilute solution behavior of several alternating copolymers of maleic acid has been characterized by static and dynamic light scattering, intrinsic viscosity, and pulsed-gradient spin-echo NMR spectroscopy. The copolymer of maleic acid–sodium salt and isobutylene (IBMA-Na, M_w ∼350 kg/mol) dissolves readily in concentrated aqueous salt solutions. Changes in chain dimensions with ionic strength and pH are similar to those of the lesser salt solution-soluble poly(acrylic acid-sodium salt). The hydrophobically modified (with n-butyl, n-hexyl, n-octyl, and phenethyl amines) copolymers of maleic acid–sodium salts and isobutylene (IBMA-NHR-Na) show no sign of large intermolecular aggregation in 0.1 N sodium acetate (NaAc). However, the sizes of the copolymers are relatively small compared to that of the ionized parent copolymer (IBMA-Na, M_w ∼350 kg/mol), suggesting intramolecular aggregation of the alkyl side-chain groups along the polymer backbone. The copolymer modified with the longer chain n-decyl, on the other hand, forms stable large intermolecular aggregates containing 33 chains/aggregate. The copolymers of maleic acid–sodium salt and styrene (SMA-Na) appear to have no signs of aggregation, despite being a hydrophobic polyelectrolyte. The copolymer of maleic acid–sodium salt and di-isobutylene (DIBMA-Na) has a similar salting-out concentration as SMA-Na. The radius of gyration measurements by static light scattering suggest that at least some fraction of the DIBMA-Na chains form large intermolecular aggregates. The copolymers of maleic acid–sodium salt with n-alkenes (n-C_mMA-Na) in 0.1 N NaAc form small intermolecular aggregates (three to five chains/aggregate). In contrast to these static light scattering results, PGSE NMR diffusion measurements for the above aggregated systems indicate only one diffusion coefficient consistent with the motion of single isolated chains. A plausible explanation for this discrepancy is that the population of the aggregates is too small to be sufficiently detected in the PGSE NMR experiment. Furthermore, it is likely that the aggregate has a larger relaxation rate than the nonaggregate, and therefore has a comparatively reduced signal in the PGSE NMR experiment. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3584–3597, 2004     

A novel sublimable organic salt: Synthesis,characterization, thermal behavior,and catalytic activity for the synthesis of arylidene,heteroarylidene, and alkylidene malonates

A novel sublimable organic salt was synthesized, and its chemical structure was characterized by FTIR, 1D NMR, 2D NMR, and elemental analysis. In addition, the thermal phase transitions and thermal stability of new organic salt were investigated. The DSC and TGA results showed that the organic salt could convert into constituent molecules at?<?145 °C before decomposition temperature (T_dec.?~?200 °C) under atmospheric pressure without forming the liquid phase. Then, it was recondensed to regenerate the initial organic salt in the cool part of the vial. Therefore, it can be a promising organic salt towards the regeneration of spent catalyst from synthesis processes when the reaction mixture contains poorly volatile components and includes its use in gas-phase procedures. Also, the catalytic efficiency of new organic salt was investigated in the Knoevenagel condensation reaction. A variety of substituted arylidene and alkylidene malonates were isolated in 78–95% yield within six hours.? Under the optimized reaction conditions, the current catalytic procedure exhibited superiority compared to the mixed piperazine/acetic acid, piperidine/acetic acid, and piperidinium acetate. There were no significant changes in the new organic salt chemical structure and catalytic activity even after the 5th run. This work revealed the importance of the existence of simultaneous hydrogen bond acceptor/donor groups in our environmentally friendly catalyst to promote the Knoevenagel condensation reaction without the use of metal-containing catalysts.

     

Synthesis,Structure, and Properties of Novel Enamine Containing Coumarin and Phosphonium Fragments

Condensation of 4-hydroxy-3-formylcoumarin with 4-aminobenzyl(triphenyl)phosphonium bromide has led to the formation of a phosphonium salt existing in DMSO solution as a mixture of two enamine forms, Z and E, according to NMR spectroscopy and quantum-chemical simulations data. Basing on the obtained salt, the ML₂ metal chelates of zinc(II), copper(II), and nickel(II) have been synthesized. Luminescence properties of the ligand and its complex with zinc have been studied.

     

Photophysical and rheological properties of naphthalene-labeled cationic poly(dimethyl sulfate quaternized acrylamide/N,N-dimethylaminopropylmaleimide copolymer)

The synthesis, rheological, and fluorescence properties of a cationic water-soluble copolymer, naphthalene-labeled cationic poly(dimethyl sulfate quaternized acrylamide/N,N-dimethylaminopropylmaleimide copolymer), poly(DSQADMAPM)/NA, are reported. When fluorescent hydrophobes (naphthyl group) are incorporated into the cationic copolymer, the photophysical response may effectively probe solution behavior on the microscopic level. The salt and pH responsiveness inherent to the cationic copolymer systems is a function of ionic group type. Experimental results indicate that I_E/I_M increases steadily with increases in polymer concentration and I_E/I_M values for a given polymer concentration are higher in salt. At low pH values, I_E/I_M is high and excimer emission increases as the quaternary amino groups (R₄N⁺) are screened out. Dynamic light scattering (QELS) measurements indicate that diffusion coefficients of the cationic copolymer increase and the hydrodynamic diameters decrease with increasing salt concentration. Viscosity studies reveal that the polymer coil shrinks as salt is added. In fluorescence quenching study, the reduction in the quenching efficiency of thallium (Tl⁺) with salt addition can arise from enhanced compartmentalization of naphthalene labels as added electrolyte enhances intrapolymer micellization. The intrapolymer micelle is easily formed, indicating that the thallium ion has difficulty in reacting with bound naphthalenes located in the shrunk polymer coil. The cationic copolymer is depicted as an expanded polymer coil in deionized water because of intra- and interchain repulsions. Consequently, salt addition breaks down the repulsions and enhances intrapolymer micellization. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 11–19, 1998     

Synthesis of gluco-Configured Tetrahydroimidazopyridine-2phosphonate-Derived Lipids,Potential Glucosyl Transferase Inhibitors

The analogues 1 – 3 of dolichol monophosphatidyl β-D -glucose have been prepared as potential inhibitors of the glucosyl transferase Alg10p. Pd(PPh₃)₄-catalysed phosphonylation of the iodoimidazole 4 with diethyl, dimethyl, and diphenyl phosphite led to the corresponding phosphonic acid diesters, which were transformed into deprotected and silyl-protected diesters, deprotected monoesters, and protected and unprotected phosphonic acids (Scheme). A N-methyl imidazolium salt was obtained as a by-product of the dimethyl-phosphonylation of the iodoimidazole, and prepared in high yields by methylation of the imidazole 8 with MeI; the corresponding deprotected salt 11 inhibits sweet almond β-glucosidases (IC₅₀=308 μM ). Trichloroacetonitrile-promoted monoesterification of the acetylated mono-triethylammonium salt 19 with oleyl alcohol, phytanol, and dolichol-19, followed by deacetylation, gave the desired glycophospholipids.     

A practical synthesis of novel hydroxyl-substituted macrocyclic tri-, tetra- and hexa-mines

Macrocyclic tri- and tetra-amines containing a hydroxyl group in the ring have been preparad in moderate yields by a 1:l cyclocondensation of 1,3-dichloro-2-propanol with the disodium salt of N-tosylated diethylenetriamine and triethylenetetraamine. In the case of condensation of 1,3-dichloro-2-propanol with the disodium salt of N-tosylated diethylenetriamine, the 2:2 cyclocondensation product, dihydroxyl macrocyclic hexaamine, was also isolated.     

Crystal structure,spectroscopic and thermal studies of anhydrous potassium 2,6-dihydroxybenzoate

The crystal structure, infrared spectrum and thermal stability of the potassium salt of 2,6-dihydroxybenzoic acid have been studied. The compound crystallizes in the monoclinic space group P2₁/n with a = 3.847(1) Å, b = 15.099(5) Å, c = 13.248(4) Å, β = 98.35(2)° and Z = 4. The compound of the general formula KL is a three-dimensional polymer, in which K ions are bridged by coordinated organic ligands by oxygen atoms of carboxylate and hydroxy groups. The anhydrous compound decomposes at 230°C. The IR spectrum of the potassium salt is discussed.     

Photophysical and viscometric properties of naphthalene-labeled acrylamide/N,N-dimethyl maleimido propyl ammonium propane sulfonate copolymer

 The synthesis, viscometric, and fluorescence properties of a water-soluble zwitterionic sulfobetaine copolymer, poly(ADMMAPS)/NA, are reported. When fluorescent hydrophobes (naphthyl group) are incorporated into the zwitterionic copolymer, the photophysical response may effectively probe solution behavior on the microscopic level. Experimental results indicate that I _E/I _M steadily increases with increases in polymer concentration. I _E/I _M in aqueous solution is greater than that in aqueous potassium chloride solution. Dynamic light scattering (QELS) measurements show that hydrodynamic diameters of the naphthalene-labeled zwitterionic sulfobetaine copolymer increase with an increasing salt concentration. Viscosity studies reveal that the polymer coil expanded as more salt is added. In fluorescence quenching study, the reduction in the quenching efficiency of Tl⁺ with salt addition can arise from enhanced compartmentalization of naphthalene labels as added electrolyte enhances intrapolymer micellization. The intrapolymer micelle is easily formed, indicating that the thallium ion has difficulty reacting with bound naphthalenes located in the polymer coil. The naphthalene-labeled zwitterionic sulfobetaine copolymer is depicted as a compacted polymer coil conformation in deionized water because of intra-and inter-associations. Consequently, salt addition breaks up the associations and enhances the intrapolymer micellization. The microscopic and macroscopic behaviors of zwitterionic sulfobetaine copolymer differ a lot from those of the corresponding cationic copolymer. Received: 4 February 1997 Accepted: 1 May 1997     

Acetyl chloride-3,5-di(tert-butyl)-4-hydroxy-N,N-dimethylbenzylamme salt in the benzylation of organic and inorganic sulfur-containing compounds

The reactions of the quaternary acylammonium salt formed on treatment of3,5-di-tertbutyl-4-hydroxy N,N-dimethylbenzylamine with acetyl chloride, with various organic and inorganic sulfur-containing compounds were studied. The possibility of using this salt for the introduction of a sterically hindered phenol moiety in various sulfur-containing compounds was shown.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 98–102, January, 1994.     

Reactions of Alkenediazonium Salts. Part 1. 2,2-Diethoxyethene-diazonium hexachloroantimonate: A diazonium,a carbenium or an oxonium salt?

Reactions of the title compound 1 with various nucleophiles have been studied. The salt behaves like an alkylating agent towards ethers, alcohols and water forming ethyl diazoacetate ( 2 ), which reacts further with excess of the nucleophile. A solvent cage mechanism accounting for the observed products is proposed. Thermal decomposition in inert solvents leads to the alkylation of the counter-ion, i.e. formation of chloroethane, and in anisole, alkylation and chlorination of the solvent are also observed. With a standard coupling component, 2-naphtholate ion, no azo coupling reaction of 1 is observed, but instead 14-methyl-14 H-dibenzo[a,j]xanthene ( 17 ) is formed. The products of the reaction with diethylamine are diethylcyanoformamide ( 18 ) and ethyl diethylcarbamate ( 19 ). None of the chemistry of salt 1 is explained by the intervention of vinyl cations expected to be formed in a heteroytic dediazoniation. The predominant pathways seem to involve reactions of an oxonium salt (alkylating properties) or, in the case of diethylamine, a carbenium salt (primary nucleophilic attack on the β-C-atom of 1 ). The free energy barrier to C?C rotation in 1 is estimated to be 75 to 77 kJ/mol (18.0 to 18.5 kcal/mol), a value which falls between those expected for a double and a single bond.     

Micellization through complexation of oppositely charged diblock copolymers: Effects of composition,polymer architecture,salt of different valency,and thermoresponsive block

The structural and electrical characteristics of polyelectrolyte complex micelles (PCMs) formed by mixing of oppositely charged double hydrophilic copolymers are studied by means of molecular dynamics simulations. In mixtures of linear diblock copolymers we found that the preferential aggregation number N_p of PCMs is a universal function of the ratio γ_± of the total positive to total negative charges of the mixture. The addition of divalent salts ions induces a secondary micellization. In mixtures of copolymers bearing a common neutral thermoresponsive block, micelles with contracted corona consisting of thermoresponsive blocks and complex polyelectrolyte core are formed at low salt concentration and temperature far away the biphasic regime. At high salt concentration and temperature in the biphasic regime, reversed micelles are obtained. In equimolar mixtures of linear copolymers with miktoarm stars we found that N_p of PCMs decreases as the number of charged branches of miktoarm copolymer increases. The shape of micelles progressively changes from spherical to worm-like with the increase of number of branches of miktoarm copolymers. Our findings are in full agreement with existing experimental and theoretical predictions and provides new and additional insights.     

Isolation and Characterization of a Novel Plasma Membrane Intrinsic Protein Gene, <Emphasis Type="Italic">LcPIP1</Emphasis>, in <Emphasis Type="Italic">Leymus chinensis</Emphasis> that Enhances Salt Stress Tolerance in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

A novel plasma membrane intrinsic, LcPIP1, was isolated from Leymus chinensis using RACE method. The LcPIP1 has 288 amino acids with an estimated molecular mass of 30.6 kDa. Semi RT-PCR analysis indicated that the expression level of LcPIP1 was obviously higher in leaf than root. The LcPIP1 was also found to be induced by salt stress. In addition, transformed with the LcPIP1, Saccharomyces cerevisiae could increase tolerance to salt stress. These results indicate that the LcPIP1 gene seems to play a role in resistance against salt stress.     

Kinetics of Alkylated Biladiene-a,c Deprotonation

The kinetics of deprotonation of 1,3,7,13,17,19-hexamethyl-2,8,12,18-tetrabutylbiladiene-a,c dyhydrobromide on treatment with nucleophilic reagents (pyridine, dimethylformamide, dimethyl sulfoxide) in carbon tetrachloride was measured by electron absorption spectroscopy in the temperature range of 293.15–303.15 K. The effects of the reactant concentrations, the temperature, and the electron-donor properties of the nucleophilic reagent on the kinetics of deprotonation of biladiene-a,c as the salt with HBr are discussed.     

Modified carrageenan. 5. Preparation,swelling behavior,salt‐ and pH‐sensitivity of partially hydrolyzed crosslinked carrageenan‐graft‐polymethacrylamide superabsorbent hydrogel

The polysaccharide, kappa‐carrageenan (κC) was chemically modified to achieve a novel superabsorbent hydrogel via graft copolymerization of methacrylamide (MAM) onto the substrate followed by alkaline hydrolysis. Ammonium persulfate (APS) and N,N′‐methylene bisacrylamide (MBA) were used as a free‐radical initiator and a crosslinker, respectively. The saponification reaction was carried out using sodium hydroxide aqueous solution. Either κC‐g‐PMAM or hydrolyzed κC‐g‐PMAM (PMAM: polymethacrylamide) was characterized by FT‐IR spectroscopy. The effect of grafting variables (i.e. concentration of MBA, MAM, and APS) and alkaline hydrolysis conditions (i.e. NaOH concentration, hydrolysis time and temperature) were systematically optimized to achieve a hydrogel with swelling capacity as high as possible. The swelling capacity of these hydrogels was also measured in various salt solutions. Results indicated that the swelling ratios decreased with an increase in the ionic strength of the salt solutions. This behavior can be attributed to charge screening effect for monovalent cations, as well as ionic crosslinking for multivalent cations. Absorbency of superabsorbing hydrogels was examined in buffer solutions with pH range 1–13. Also, the pH reversibility and on–off switching behavior, at pH values 3.0 and 8.0, makes the synthesized hydrogels good candidates for controlled delivery of bioactive agents. Finally, swelling kinetics in distilled water and various salt solutions was preliminary investigated. Results showed that the swelling in water was faster than in saline solutions. Copyright © 2004 John Wiley & Sons, Ltd.     

The Enantioselective Synthesis of 3-Methoxy-1, 3, 5 (10)-estratrien-11, 17-dione by a Thermal Intramolecular Cycloaddition Reaction. Preliminary communication

The enantiomerically pure (+)-3-methoxy-1, 3, 5 (10)-estratrien-11, 17-dione 11 (with trans-anti-trans configuration) was synthesized in a highly stereocontrolled fashion from (±)-t-butyl 4-methoxy-1-benzocyclobutene carboxylate (8) and the (+)-carboxylic acid 6 , obtained from 4 in two steps, followed by one crystallization of the (+)-ephedrine salt. The key step 10→11 (Scheme 2) involves a thermal intramolecular cycloaddition reaction.     

Conversion of 3,7-Dialkoxy-4H,8H-benzo[l,2-c:4,5-c']diisoxazole-4,8-dione into new heterocyclic systems

Treatment of 1a or 1b with concentrated acids yielded the acid 3 , with alkali hydrogen carbonates the sodium salt 7 and the potassium salt 8 ; by reacting with phosphorus pentachloride the vinylogous acid chloride 9 was isolated. Reactions of 9 with amines such as N-nucleophiles led to the corresponding amides 10, 11, 14, 15 , and with alcohols such as O-nucleophiles to the corresponding alkoxyderivatives 16a, 16b , which are isomeric compounds to 1a, 1b and 2a, 2b.     

Continuous Miscibility from Dilute Solution to Fused Salt: Volumetric Properties of Binary Solutions of Nitrobenzene, 1-Butanol, and Anisole with Tetra-n-Butylammonium Picrate from 298.15 to 371.1 K

The densities and speeds of sound of binary solutions of nitrobenzene, 1-butanol, and anisole with tetra-n-butylammonium picrate have been measured over the full composition range from 298.15 to 371.1 K, in order to study the volumetric behavior of continuously miscible systems, made from an organic fused salt and a molecular organic liquid, at just above the melting point of the salt. The calculated apparent molar volumes and compressibilities are analyzed by using the equations of Petrenko and Pitzer. The thermal expansion coefficients of the above systems are also reported.     

Efficient access to bisphenol A metabolites: Synthesis of monocatechol,mono-o-quinone,dicatechol, and di-o-quinone of bisphenol A

2-Iodoxybenzoic acid (IBX) oxidation of bisphenol A (BPA) is described. The selective production of either the mono-o-quinone or the di-o-quinone can be controlled by IBX stoichiometry. Isolated yields of quinone were greater than 80%. Previous synthesis of BPA-di-o-quinone using a large excess of Fremy’s salt produced only trace amounts of product. In addition to o-quinone products, both mono- and dicatechols of BPA can synthesize in high yield and isolated without chromatography. The more stable catechols can be quantitatively converted back to o-quinones using silver oxide oxidation in either acetone or DMF. These one-pot reactions provide access to four different BPA metabolites in high yield and significant scale.     

Synthesis, spectrophotometry, and X-ray diffraction studies of a new salt: p-xylylenebis(tetrahydrothiophenium) bis(triiodide)

A new salt, p-xylylenebis(tetrahydrothiophenium) bis(triiodide) C₁₆H₂₄I₆S₂, was prepared. The molecular structure of the salt was studied by X-ray diffraction; the factors that form the crystal packing represented by...Ct...I₃...I₃...Ct... type chains (Ct is cation) were identified. The stability of p-xylylenebis(tetrahydrothiophenium) diiodochlorides and triiodides was estimated by spectrophotometry using the average iodine number function . Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1341–1344, July, 2007.