A versatile reagent for synthesis of α-hydroxy aldehydes and ketones —methylthiomethyl p-tolyl sulfone

Methylthiomethyl p-tolyl sulfone (1) can be utilised for synthesizing α-hydroxy ketones as well as α-hydroxy aldehydes, the hydroxyl group of which is protected with acetyl, tetrahydropyranyl, or methoxymethyl group.     

Hydrodynamic focusing—a versatile tool

The control of hydrodynamic focusing in a microchannel has inspired new approaches for microfluidic mixing, separations, sensors, cell analysis, and microfabrication. Achieving a flat interface between the focusing and focused fluids is dependent on Reynolds number and device geometry, and many hydrodynamic focusing systems can benefit from this understanding. For applications where a specific cross-sectional shape is desired for the focused flow, advection generated by grooved structures in the channel walls can be used to define the shape of the focused flow. Relative flow rates of the focused flow and focusing streams can be manipulated to control the cross-sectional area of the focused flows. This paper discusses the principles for defining the shape of the interface between the focused and focusing fluids and provides examples from our lab that use hydrodynamic focusing for impedance-based sensors, flow cytometry, and microfabrication to illustrate the breadth of opportunities for introducing new capabilities into microfluidic systems. We evaluate each example for the advantages and limitations integral to utilization of hydrodynamic focusing for that particular application.     

A versatile and concise route to functionally substituted γ-butyrolactones and spiro-XXX-butyrolactones (lactone annelation)

A novel route to the synthesis of functionally substituted XXX-butyrolactones and spiro-γ-butyrolactones, from six-membered cyclic enol-esters, is described.     

A versatile and selective chemo-enzymatic synthesis of β-protected aspartic and γ-protected glutamic acid derivatives

Two versatile, high yielding, and efficient chemo-enzymatic methods for the synthesis of β-protected Asp and γ-protected Glu derivatives using Alcalase are described. The first method is based on the α-selective enzymatic hydrolysis of symmetrical aspartyl and glutamyl diesters. The second method involving mixed diesters comprises a three-step protocol using (i) α-selective enzymatic methyl-esterification, (ii) chemical β-esterification, and finally (iii) α-selective enzymatic methyl ester hydrolysis. The yields of the purified β- and γ-esters range from 77% to 91%.     

A direct link between the Passerini reaction and α-lactams

α-Lactams (aziridinones) can function to replace two of the three reactants, the oxo-compound and the isonitrile, in the Passerini reaction. Four α-lactams (5a-d) were reacted with mono- and dicarboxylic acids of positive pK_a values to give 2-acyloxycarboxamides (4) and bis-2-acyloxycarboxamide products 12 and 13, respectively. The same compounds were also prepared via the Passerini reaction. Acids with a negative pK_a decarbonylate α-lactams to give immonium salts. The main path of the reaction depends on the pK_a of the acid component, the reactivity of the α-lactam, and the reaction conditions.     

Study on forced hydrolysis reaction of acidic Fe2(SO4)3 solution—structure and properties of precipitates

The phase composition, morphology, and inner structure of the particles precipitated from a forced hydrolysis reaction of acidic Fe₂(SO₄)₃ solution were examined. The shape and size of precipitated particles strongly depended on the concentration of the reactants in the starting solution, particularly on that of Fe₂(SO₄)₃. The relatively lower concentration of Fe₂(SO₄)₃ produced acicular or rod-like multi-domainic goethite particles, while the higher one provided irregularly shaped hydronium jarosite particles. This difference strongly depended on the pH of the aging solution; acicular goethite particles were produced at pH≥1.6 though jarosite was produced at pH≤1.5. The large goethite and jarosite particles exhibited a high microporosity. The time resolved transmission electron microscope (TEM) observation technique revealed that the rate of hydrolysis reaction for producing goethite was fast and the particle growth was almost terminated after aging for 1 day. On the contrary, the system favoring precipitation of jarosite exhibited a phase transformation from cubic and hexagonal basic iron(III) sulfate, produced in the early stage of the reaction until 10 h, to large irregular jarosite particles.     

Production and properties of polyacenaphthylene—V dilute solution properties

Polyacenaphthylene was synthesized by thermal bulk polymerization, fractionated into 11 fractions by fractional precipitation and characterized by gel permeation chromatography, light scattering and osmometry. Long chain branching was observed in polyacenaphthylenes with $\text{M}{}_{\mathrm{<mtext>w</mtext>}}\text{> 1 × 10}{}^6\text{g/mol}$. θ-temperatures of branched and linear polyacenaphthylenes were determined in 1,2-dichloroethane and are different in magnitude. Polyacenaphthylene undergoes chemical degradation in manufacturers' grade 1,2-dichloroethane. Intrinsic viscosities in benzene, toluene, tetrahydrofuran at 25°C, and in 1,2-dichloroethane at 41.1°C have been measured and the Mark-Houwink constants of the viscosity molar mass relationship evaluated.     

Gamma radiolysis of Methyl Red solution and reaction induced by γ-irradiated NaCl in Methyl Red

The -radiolysis of Methyl Red solution in HCl medium at pH=2 has been studied along with energy transfer reaction brought about byF and hole centers of -irradiated NaCl. The G-values for degradation of the azo dye indicator by radiolysis and -irradiated salt were determined as 9·10^–1 and 4.8·10^–3, respectively. The kinetic rate constants (k) of degradation are evaluated as 2·10^–5 rad^–1 in the case of direct radiolysis, while for the irradiated salt it is 2·10^–7 rad^–1. The extent of degradation by direct -radiolysis is 100–200 times greater as compared to that by the -irradiated salt. The same mechanism is proposed for radiolysis as well as the reaction induced by -irradiated sodium chloride.     

A versatile synthetic strategy for nanoporous gold–organic hybrid materials for electrochemistry and photocatalysis

Nanoporous gold (npAu) was employed as high surface area substrate for immobilization of redox- and photooxidative-active organic molecules. A two-step synthetic routine is demonstrated as a versatile and robust method for immobilization of various molecules. First, self-assembled monolayers (SAMs) of thiols containing an azide moiety were prepared on npAu substrates. Then, alkyne-modified ferrocene, tetrathiafulvalene, and zinc(II)phthalocyanine derivatives were covalently bound via the click reaction to this linker. Following the provided synthetic procedures high performance composite materials are generated for electrochemistry and photochemistry. The robust bonding between the organic functional group and the gold support provides stability even under strongly oxidizing conditions (applied potential or singlet oxygen).     

Anation reactions involving bidentate ligands—I: The reaction between oxalate and diaquatetraamminecobalt(III) ion in acid aqueous solution

The reaction of diaquatetraamminecobalt(II)) ion with oxalate was found to occur in a single stage. The rate law is interpreted in terms of an ion pairing mechanism with an ion pairing equilibrium constant of 0.52 for H₂C₂O₄ and 5.3 for HC₂O₄⁻.     

A dioxotetraamine fluorenyl ligand and its nickel(II) complex — crystal structure and fluorescent sensing properties in aqueous solution

A new ligand consisting of fluorenyl and dioxotetraaza units, namely, 2,10-diamino-6-(9H-fluoren-9-yl)-4,8-diazaundecane-5,7-dione (L), and its nickel(II) complex were synthesized. The crystal structure of [Ni(H₋₂L)] showed that Ni(II) is in a square planar coordination environment. Studies of solution chemistry of the ligand and its nickel(II) complex indicate that the ligand can form a stable complex with Ni²⁺ ions and fluorescence quenching of the ligand is accompanied by the coordination of the metal ion to the dioxotetraaza unit and electron transfer from the Ni(II) center to fluorenyl in aqueous solution.     

A versatile and straightforward approach to the 21-oxidation of β-substituted and α,β-unsaturated 20-oxosteroids

21-Hydroxylation and acetoxylation of 20-oxosteroids, either α,β-unsaturated or β-substituted, were successfully achieved through oxidation of the corresponding silyl enol ethers withm-CPBA followed by smooth hydrolytic cleavage of the 21-alkylsilyloxy derivatives. These conditions, which have not been previously used to synthesize such compounds, allow a high degree of regio and chemoselectivity and are specially useful for the chemical synthesis of 16α,21-dihydroxy-20-oxosteroids.     

Hydrogen evolution and oxidation—a prototype for an electrocatalytic reaction

Due to progress in the theory of electrocatalysis and in quantum chemistry, it has become possible to investigate the hydrogen reaction and perform quantitative calculations for the reaction rate. First, we demonstrate this with model calculations for the adsorption of hydrogen on Pt(111). In accordance with experimental data, we find hydrogen adsorption at a potential above the equilibrium potential and with an almost vanishing energy of activation. As a second example, we explain trends in the catalytic activity of palladium overlayers and clusters on Au(111) electrodes. Dedicated to J.O’M. Bockris on the occasion of his 85th birthday and in recognition of his contributions to electrochemistry.

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An optically active allene macrodiolide: A versatile key intermediate leading to (−)-pyrenophorin and (+)-dibenzomacrodiolides

The optically active allene macrodiolides via the macrocyclization of allenic ester provide a simple route to (−)-pyrenophorin and (+)-dibenzomacrodiolide, respectively.     

Tungsten electrochemistry in alkaline solutions—Anodic dissolution and oxygen reduction reaction

Oxygen reduction reaction (ORR) was investigated in alkaline solution on tungsten electrode subjected to a previous anodic dissolution. The rotating disk cyclic voltammetry and rotating disc chronoamperometry were used. Both unsupported and potassium pechlorate and sulfate supported solutions were examined. The most striking feature of recorded ORR curves is the large difference of ORR overpotential during anodic and cathodic sweep. This was attributed to the formation of tungsten oxide on the surface. It was demonstrated that electrode pretreatment as well as the electrolyte composition greatly affects ORR electrochemistry on tungsten electrode, and the influence of sulfates is discussed.     

Does capillarity influence chemical reaction in drops and bubbles? A thermodynamic approach

After a brief introduction on the variables which describe the physico-chemical properties of a fluid surface, this paper compares, in a very simple way, the equilibrium constant of homogeneous and heterogeneous reactions taking place in spherical micro-objects (uncharged and charged droplets and bubbles) and in media bordered by a flat interface. This quantity is by definition the exponential of the dimensionless standard chemical affinity whose values (< or = 0, > or = 0) may indicate the direction and the importance of the reaction (strictly true when the mixing term of the affinity is zero). The classical thermodynamic approach combined with the Laplace equation shows that: (i) high surface tension and high curvature influence the equilibrium constant, this effect being, however, much more important for bubbles than for droplets; (ii) charges on droplets reduce this effect; (iii) the constant of reaction taking place in the vapour in contact with a charged droplet depends significantly on the electric field pressure; (iv) reactions in droplets dispersed in the liquid phase are discussed and, in particular, capillarity seems to play a negligible role on reactions in micro-emulsions; (v) the surface amount of a gas bubble component transferred in the continuous liquid can be related to capillary quantities; (vi) expanding (or shrinking) bubble induced by a chemical reaction is analysed by using an extended Laplace law which includes the volumetric flow rate; (vii) the Laplace law is discussed in the frame of the choice of the dividing surface. Numerous actual examples from the atmosphere, sonochemistry and metallurgy illustrate the theory proposed. One of the interest, among other points, is that small objects (specially bubbles) give the potentiality to obtain, for steady or (near) equilibrium states, large amount of components which would not be possible when dealing with large reservoirs.     

A novel regio-and stereo-specific hydrohalogenation reaction of 2-alkynoic acids and their derivatives

The nucleophilic hydrohalogenation of 2-alkynoic acids anti their derivatives byheating with lithium halides iu HOAc afforded the thermodynamically unfavorable 3-halo-2 (Z)-alkenoic acids and their derivatives stereospecifically     

A continuous-flow synthesis of annulated and polysubstituted furans from the reaction of ketones and α-haloketones

A synthesis of di-, tri- and tetra-substituted furans from reaction of the corresponding ketones and α-haloketones with LiHMDS is reported. Reaction under continuous-flow conditions gave increased yields and removed the need for external cooling when compared to the unoptimised batch conditions.     

A transformed time-dependent Michaelis–Menten enzymatic reaction model and its asymptotic stability

The dynamic form of the Michaelis–Menten enzymatic reaction equations provide a time-dependent model in which a substrate $S$ reacts with an enzyme $E$ to form a complex $C$ which in turn is converted into a product $P$ and the enzyme $E$ . In the present paper, we show that this system of four nonlinear equations can be reduced to a single nonlinear differential equation, which is simpler to solve numerically than the system of four equations. Applying the Lyapunov stability theory, we prove that the non-zero equilibrium for this equation is globally asymptotically stable, and hence that the non-zero steady-state solution for the full Michaelis–Menten enzymatic reaction model is globally asymptotically stable for all values of the model parameters. As such, the steady-state solutions considered in the literature are stable. We finally discuss properties of the numerical solutions to the dynamic Michaelis–Menten enzymatic reaction model, and show that at small and large time scales the solutions may be approximated analytically.