Stereoselective electrocatalytic transformation of arylidene- or alkylidenemalononitriles and malonate into alkyl (1R,5R,6R)* 6-substituted 5-cyano-4,4-dialkoxy-2-oxo-3-azabicyclo[3.1.0]hexane-1-carboxylates

Electrolysis of arylidene- or alkylidenemalononitriles and malonate in alcohol in an undivided cell in the presence of sodium halide as mediator results in the stereoselective formation of alkyl (1R,5R,6R)* 6-substituted 5-cyano-4,4-dialkoxy-2-oxo-3-azabicyclo[3.1.0]hexan-1-carboxylates in 50-70% yields.     

Innovative Electrochemical Strategies for Hydrogen Production: From Electricity Input to Electricity Output

Renewable H₂ production by water electrolysis has attracted much attention due to its numerous advantages. However, the energy consumption of conventional water electrolysis is high and mainly driven by the kinetically inert anodic oxygen evolution reaction. An alternative approach is the coupling of different half-cell reactions and the use of redox mediators. In this review, we, therefore, summarize the latest findings on innovative electrochemical strategies for H₂ production. First, we address redox mediators utilized in water splitting, including soluble and insoluble species, and the corresponding cell concepts. Second, we discuss alternative anodic reactions involving organic and inorganic chemical transformations. Then, electrochemical H₂ production at both the cathode and anode, or even H₂ production together with electricity generation, is presented. Finally, the remaining challenges and prospects for the future development of this research field are highlighted.     

Stereoselective electrocatalytic transformation of arylidenemalononitriles and malononitrile into (1R,5S,6R)-6-aryl-2-amino-4,4-dialkoxy-1,5-dicyano-3-azabicyclo[3.1.0]hex-2-enes

Electrolysis of arylidenemalononitriles and malononitrile in alcohols in an undivided cell in the presence of sodium bromide as mediator results in the stereoselective formation of (1R,2S,6R)^*-6-aryl-2-amino-4,4-dialkoxy-1,5-dicyano-3-azabicyclo[3.1.0]hex-2-enes in 60-80% yields.     

生物电化学传感器中煌聚合物材料

对聚合物材料在生物电化学传顺中的应用进行了评述,包括高分子媒介体化合物、高分子阻挡膜、酶固定化材料和电解聚合物材料。并指出今后提高生物电化学传感器性能、改善和改变其表面特性,也依赖于聚合物材料的应用。     

Stereoselective electrocatalytic transformation of malonate and alkylidenecyanoacetates into (E)-3-substituted 2-cyanocyclopropane-1,1,2-tricarboxylates

Electrolysis of malonate and alkylidenecyanoacetates in alcohols in an undivided cell in the presence of NaBr results in stereoselective formation of (E)-3-substituted 2-cyanocyclopropane-1,1,2-tricarboxylates in 75-90% yields.     

Electrically ‘wired’ tyrosinase enzyme inhibition electrode for the detection of respiratory poisons

The use of the solution redox species, [Os(bpy)₂Cl₂]^+/0, [Os(bpy)₂(MeIm)Cl]^2+/+ and [Fe(CN)₆]^4−/3−, where bpy is 2,2-bipyridine and MeIm is N-methylimidazole, as electron mediators in the enzymatic reduction of oxygen by tyrosinase is investigated. Co-immobilization of both enzyme and an osmium redox mediator in a hydrogel on glassy carbon electrodes results in a biosensor for the ‘reagentless’ addressing of enzyme activity, consuming only oxygen present in solution. Immobilized enzyme inhibition biosensors can thus be constructed for the detection of tyrosinase inhibitors, such as sodium azide, using this approach. The enzyme inhibition biosensor can detect levels of azide as low as 5 × 10⁻⁶ mol dm⁻³ in solution and may be useful in environmental monitoring applications and as an early warning poison sensor.     

Degradation of Polycyclic Aromatic Hydrocarbons by <Emphasis Type="Italic">Rigidoporus lignosus</Emphasis> and its Laccase in the Presence of Redox Mediators

The metabolism of polycyclic aromatic hydrocarbons (PAHs) was studied in vivo and in vitro in systems consisting of Rigidoporus lignosus and its laccase, in the presence of so-called “mediator” compounds. The static culture of the native fungal strain was able to metabolize anthracene and 2-methylanthracene, but not 9-nitroanthracene. The addition of redox mediators 2,2’-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 1-hydroxybenzotriazole (HBT) or violuric acid (VA) led to a significant increase in the degradation of substrates. The oxidation of PAHs was not significant when purified laccase was used without the addition of mediators. The addition of these compounds increased the oxidation of all substrates by approximately 70–80% after 72 h of incubation. The degradation rate was highest for 2-methylanthracene in the presence of VA.     

A UV-visible spectroelectrochemical study of the electropolymerisation of N-benzylaniline

The electropolymerisation of N-benzylaniline (NBA) at transparent ITO glass electrodes was investigated with in situ UV-visible spectroelectrochemistry. An intermediate was found to be generated during electrolysis as the precursor of poly(N-benzylaniline) (PNBA). The intermediate, which shows an absorbance band at λ = 460 nm, is able to react spontaneously with NBA, forming a polymeric end product, which is deposited on the electrode surface. UV-Vis spectra were obtained with PNBA-modified electrodes at various electrode potentials. It was shown that the colouration of the PNBA film after a positive-going potential step proceeds ca. 5 times slower than its discolouration after the reverse negative-going potential step. Anodic degradation of PNBA film was shown to proceed when holding the electrode at a sufficiently high positive potential. A linear dependence between the first-order degradation rate constant (k/s⁻¹) and electrode potential (E/V) was found in the potential range of E _RHE = +0.8 to +1.1 V: log k = a + bE, where a = −8.75 and b = 5.45 are empirical coefficients. In the whole spectral range investigated, the degradation of PNBA was found to proceed faster as compared to that of polyaniline (for polyaniline, coefficients a = −12.7 and b = 8.96 were obtained in the potential range of E _RHE = +0.85 to +1.1 V). The electrooxidation of hydroquinone, as well as the electroreduction of benzoquinone, were shown to proceed at PNBA-modified electrodes. In these processes, PNBA was shown to play the role of an electron mediator between the ITO electrode and solution phase redox species. Received: 8 January 1999 / Accepted: 27 January 1999     

Indirect electrochemical oxidation of piperidin-4-ones mediated by sodium halide-base system

Indirect electrochemical oxidation of 1-N-subsituted piperidin-4-ones in methanol in an undivided cell in the presence of sodium iodide/sodium methoxide system leads to the corresponding α-hydroxyketals in 50-80% substance yield (50-65% current yield). 2,2,6,6-Tetramethylpiperidin-4-one under the same conditions forms a mixture of methyl 2,2,5,5-tetramethyl-3-pyrrolidinecarboxylate and methyl 2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrole-3-carboxylate in 70% substance yield (60-70% current yield) via electrochemically induced Favorskii rearrangement.     

Electrocatalytic multicomponent cyclization of an aldehyde, malononitrile and a malonate into 3-substituted-2,2-dicyanocyclopropane-1,1-dicarboxylate—the first one-pot synthesis of a cyclopropane ring from three different molecules

Electrolysis of an aldehyde, malononitrile and a malonate in an alcohol in an undivided cell in the presence of sodium acetate-sodium halide as a double mediatory system results in the formation of 3-substituted-2,2-dicyanocyclopropane-1,1-dicarboxylates in 40-60% yields.