DEHYDROCHLORINATION OF α-CHLORO SULFONES WITH KOH-T-BUOH: KINETIC VS EQUILIBRIUM CONTROL OF THE FORMATION OF α, β-UNSATURATED SULFONES AND THE β-T-BUTOXY AND β-HYDROXY MICHAEL ADDUCTS

Abstract

Inorganic sulfur compounds are used by microorganisms (bacteria, fungi, algae) and plants for assimilation, i.e. biosynthesis of sulfur-containing cell constituents.

Quantitatively, within the biogeochemical cycle of sulfur the utilization of inorganic sulfur compounds in bacterial energy metabolism, i.e. dissimilatory sulfur utilization, is of far higher importance. Reduced sulfur compounds serve as electron donors for photosynthesis and respiration, whereas inorganic sulfur compounds of oxidation levels above sulfide serve as electron donors in anaerobic respiration as well as in fermentation. In still other bacteria reduced sulfur compounds act as protective agents against hydrogen peroxide.     

HIGH YIELD SYNTHESIS OF α-ALKOXYPHOSPHONIUM SALTS AND α-ALKOXYPHOSPHONATES

Abstract

The recent work of Ley et al. ¹ on α-alkoxyphosphorane compounds from cyclic enolethers has prompted us to report our findings in this area. In addition to cyclic enol ethers we have studied the acyclic case as well as the use of phosphite in place of triphenylphosphine. Using this approach we have prepared alkoxy-as well as 5-and 6-membered oxyheterocyclic phosphonium salts and phosphonates in high yield.     

STEPWISE SYNTHESIS OF SiOSiN-RINGS AND CAGES

Aminosilanols can be stabilized kinetically, e.g. (Me ₃ C) ₂ Si(OH)NH ₂ , which crystallizes in ladder like chains via H-bridges. Its lithium salt was characterized as tetramer, forming a Li─O cubane, while the sodium and potassium salts are hexagonal prisms. The aminosilanol reacts with halosilanes to give amino-1,3-siloxanes. Lithium salts of amino-1,3-disiloxanes were isolated as amido-1,3-siloxanes or silylamino-silanolates. This includes a 1,3-silylgroup migration from the oxygen to nitrogen atom. Lithium salts of fluorofunctional amino-1,3-disiloxanes were characterized by X-ray. They crystallize as monomers or dimers and have unusual types of structures. LiF-elimination from such lithium salts leads to the formation of four- or eight-membered (SiNSiO)-ring systems. The chemical behavior of aminosilanols, the formation of structural isomers and of different ring systems are proved by experiments, crystal structures, and quantum chemical calculations.     

Spectroscopic and antimicrobial studies of La, Pr, Nd and Gd complexes of a dipodal [N,N,N] chelating ligand

The lanthanide complexes of bis(benzimidazole-2′-yl-methyl)amine (BImz) having molecular formula [M(BImz)X₃H₂O]·nH₂O (M = La, Pr, Nd, or Gd; X = Cl or ClO₄ and n = 1, 2 or 3) were prepared and characterized spectroscopically through IR, ¹H and ¹³C NMR, FAB-mass, UV–visible and luminescence spectroscopy. TGA data suggested presence of coordinated and the lattice water. The oscillator strengths of the f–f transitions and the covalency parameters (β, b^1/2 and δ) have been evaluated from the electronic spectral data. The proposed hepta-coordinate geometry for the complexes has been ascertained from the molecular model computations. CV studies indicate formation of a stable quasi-reversible redox couple Gd^III/IV in the solution. The in vivo antimicrobial activities of the complexes have been evaluated against gram +ve and gram −ve bacteria and fungi.     

Regioselectivity in 2-X-pyrazine aminations by O-mesitylenesulfonylhydroxylamine

The regioselectivity of 2-X-pyrazine aminations by O-mesitylenesulfonylhydroxylamine was studied experimentally and the results are discussed from the viewpoint of electronic and steric factors. DFT calculations are consistent with the reaction proceeding according to an S_N2 mechanism.     

Rearrangements of tetrahydroimidazo[1,5-b]isoxazole-2,3-dicarboxylates to pyrrolo[1,2-e]imidazol-6-ols, precursors of 2,5-dihydro-1H-pyrrole derivatives

Isoxazolines 2 from the cycloaddition of imidazoline 3-oxides 1 with DMAD rearrange in the presence of methoxide to give cis-3-methoxy-7-(methoxycarbonyl)-2,7a-diaryl-5-oxo-2,3,5,7a-tetrahydro-1H-pyrrolo[1,2-e]imidazol-6-olates 3 with 100% de. The acidic hydrolysis of 3 led to kinetically controlled formation of methyl 1-formyl-4-hydroxy-5-oxo-2-phenyl-2-((arylamino)methyl)-2,5-dihydro-1H-pyrrole-3-carboxylates 6a-e. The intramolecular transformylations of the latter to the corresponding (E)- and (Z)-methyl 4-hydroxy-2-((N-(aryl)formamido)methyl)-5-oxo-2-phenyl-2,5-dihydro-1H-pyrrole-3-carboxylates 7a-e were shown to be substituent dependent (correlate with σ) and characterized by Hammett type equations. The effect of temperature was investigated and the ρ constants determined for the same reaction series at 50, 60 and 70 °C. The amide diastereomeric ratio [(E)-7]/[(Z)-7] is substituent dependent and can be described by the equation log[(E)]/[(Z)]_x=−ρσ_I+log[(E)]/[(Z)]_x=H.     

镧系盐催化合成辣椒酯衍生物研究

对比研究了三氯化铕,三氯化镧,三氯化铈和三氯化镨四种镧系盐催化剂化学选择酯化香草醇收率的影响。以三氯化镧为化学选择催化剂,且香草醇与三氯化镧物质的量比为1：0.005时,癸酸香草醇酯的收率最高为85%,并用该法合成辛酸香草醇酯和月桂酸香草醇酯,其收率分别为87%和71%。     

The antibacterial finish of cotton via sols containing quaternary ammonium salts

The sols containing quaternary ammonium salts were prepared via sol-gel process. The effects of the molar rate of HCl, H₂O and EtOH to TEOS on the sol viscosity were investigated in detail. Cetyltrimethylammonium bromide (CTAB), Octadecyl dimethyl benzyl ammonium chloride (DC) and Ethylene-Bis (Octadecyl trimethyl ammonium chloride) [E-Bis(OTAC)]were added in the sols and applied to cotton samples by treated. The antibacterial activities of the samples were assessed against both Escherichia coli and Staphylococcus aureus bacteria. The samples treated by E-Bis(OTAC) sol exhibited the satisfactory antibacterial activity that resulted from the more microorganism adsorption and hydrophobicity. The antibacterial activities were still excellent after 10 times washings comparison with the control samples.     

Phosphonium Salts as Chiral Phase‐Transfer Catalysts: Asymmetric Michael and Mannich Reactions of 3‐Aryloxindoles

It′s a PTC : A highly efficient reaction of 3‐aryloxindoles in an asymmetric Michael addition was achieved by using a quaternary tetraalkylphosphonium salt as a chiral phase‐transfer catalyst (PTC). The products were obtained in quantitative yields high ee values. The reaction of 3‐aryloxindoles in an asymmetric Mannich reaction using the same catalyst also proved to be feasible.

     

Ferrocene–β‐Cyclodextrin Conjugates: Synthesis,Supramolecular Behavior,and Use as Electrochemical Sensors

Ferrocene with a β‐cyclodextrin unit bound to one or both cyclopentadienyl rings through the secondary face were conveniently synthesized by regiospecific copper(I)‐catalyzed cycloaddition of 2‐O‐propargyl‐β‐cyclodextrin to azidomethyl or bis(azidomethyl)ferrocene. The supramolecular behavior of the synthesized conjugates in both the absence and presence of bile salts (sodium cholate, deoxycholate, and chenodeoxycholate) was studied by using electrochemical methods (cyclic and differential pulse voltammetry), isothermal titration calorimetry, and NMR spectroscopy (PGSE, CPMG, and 2D‐ROESY). These techniques allowed the determination of stability constants, mode of inclusion, and diffusion coefficients for complexes formed with the neutral and, in some cases, the oxidized states of the ferrocenyl conjugates. It was found that the ferrocenyl conjugate with one β‐cyclodextrin unit forms a redox‐controllable head‐to‐head homodimer in aqueous solution. The ferrocene–bis(β‐cyclodextrin) conjugate is present in two distinguishable forms in aqueous solution, each one having a different half‐wave oxidation potential for the oxidation of the ferrocene. By contrast, only one distinguishable form for the oxidized state of the ferrocene–β‐cyclodextrin conjugate is detectable. The redox‐sensing abilities of the synthesized conjugates towards the bile salts were evaluated based on the observed guest‐induced changes in both the half‐wave potential and the current peak intensity of the electroactive moiety.