Hans Zimmer

A Convenient Synthesis of 3-Alkylthiophenes

Abstract The known procedures for the synthesis of 3-alkylthiophenes are rather lengthy or involved. By using the NiDPPP++ catalyzed cross-coupling method between 3-bromothiophene and Grignard reagents derived from alkyl halides a number of 3-alkylthiophenes have been prepared in a one-step reaction in good to excellent yields.

THE ELECTROCHEMISTRY OF NEUROTRANSMITTERS AT CONDUCTING ORGANIC POLYMER ELECTRODES : ELECTROCATALYSIS AND ANALYTICAL APPLICATIONS

The electrooxidation of catechols, catecholamines and NADH at conventional electrode materials is generally characterized by high degrees of irreversibility as well as strong adsorption and, hence, fouling by reactants and/or products of the reactions. On the contrary, the rates of the electron transfer are highly catalysed by the use of conducting polymer films, such as poly(3-methylthiophene), polyphenylene, polyanaline and polypyrrole, as described here. Furthermore, the usual fouling problems are eliminated. Even interference from electroinactive large proteins, such as haemoglobin, and other surfactants are substantially reduced. Also, electron spectroscopy for chemical analysis, energy-dispersive analysis of X-rays, theoretical diffusion coefficient calculations, metal ion coordination, solution diffusion analyses of cyclic voltammograms etc. show that the electron transfer occurs at the polymer-solution interface and not at the inert electrode substrate surface after diffusion through the polymer matrix or through pores. The analytical application of these polymer electrodes as amperometric detectors for flow injection analysis and high performance liquid chromatography are given. In addition, selective potentiometric electrodes for catecholamines based on conducting polymer films of crown ethers, such as binaphthyl-20-crown-6, dibenzo-18-crown-6, etc., have been developed and characterized. These potentiometric detectors significantly decrease the usual interferences of ascorbic acid, uric acid and acetaminophen found in amperometric detection.

A Convenient Synthesis of 2,5-Thienylene Oligomers; Some of Their Spectroscopic and Electrochemical Properties

Abstract A convenient synthesis of a number of oligomeric thiophcnes and oligomeric methyl-, and ethyl-substituted thiophenes as building blocks for novel conducting polymers is reported. The synthesis is based on a NiCl2(dppp) (dppp = Ph2PCH2CH2CH2;PPh2) catalyzed coupling reaction between appropriately substituted bromothiophenes and Grignard compounds derived of them. The λmax of the UV spectra of the unsubstituted oligomeric thiophenes increases, as expected, with the number of thiophene units in the oligomers. Also, as expected, the oxidation potential Emax of these compounds decreases with increasing the number of thiophene units. In the series of the methyl- or ethyl-substituted oligomeric thiophenes such a clear cut relationship is not observed. This behavior is discussed on the basis of diminishing coplanarity due to steric hindrances by the alkyl groups in the 3,3′-positions, which results in a blue shift of the λmax of the UV spectra and a decreased stability of the radical cation formed upon e...

Electrochemistry and detection of some organic and biological molecules at conducting poly(3-methylthiophene) electrodes

Electrodes modified by the electrodeposition of poly(3-methylthiophene) were used as chemical sensors for some organic and biological molecules of industrial and medicinal interest. The electrochemical behaviors of ferri/ferrocyanide, catechol, ascorbic acid, hydroquinone, dopamine epinephrine, acetaminophen, p-aminophenol and NADH were examined by cyclic voltammetry. The results showed that the proposed modified surface catalyzes the oxidation of these compounds. Differential pulse and square wave techniques were used for the analysis of binary mixture of ascorbic acid with catechol, NADH, dopamine and p-aminophenol. Voltammetric peak resolution was also demonstrated for a ternary mixture of ascorbic acid, catechol and p-aminophenol. Polymer coated electrode was also used in an amperometric detector for flow injection analysis of most of the aforementioned compounds. The responses of the polymer electrode were 4-10 times larger as compared to those of platinum. The modified electrode displayed excellent response stability for successive injections and detection limits were 10 ppb for catechol, dopamine, epinephrine, NADH and p-aminophenol, 1 ppb for acetaminophen and 100 ppb for ascorbic acid. Voltammetric peak positions were affected by the nature of the electrolyte and its pH. Also, film thicknesses were shown to be a factor affecting both the current magnitudes and oxidation peak potential of NADH.

Induction of antibodies to nuclear antigens in rabbits by immunization with hydralazine-human serum albumin conjugates.

The antihypertensive drug hydralazine can induce in man a syndrome similar to spontaneous systemic lupus erythematosus (SLE). The pathogenesis of this drug-induced syndrome is not understood. In this investigation, five groups of rabbits were studied: group I, 10 rabbits hyperimmunized with hydralazine conjugated to human serum albumin (HSA) in complete Freunds adjuvant (CFA); group II, four rabbits with HSA in CFA; group III, four rabbits with CFA alone; group IV, five rabbits with hydralazine conjugated to rabbit serum albumin (RSA); and group V, four rabbits with a major metabolite of hydralazine conjugated to HSA. The rabbits immunized with hydralazine-HSA developed rising titers of antibodies to hydralazine and progressively increasing amounts of antibodies to both single-stranded and native DNA. The antibodies to DNA were cross-reactive with hydralazine as determined by inhibition of DNA binding and DNA hemagglutination tests. Similar results were obtained in rabbits immunized with the metabolite-HSA compound except the major hapten antibody response was to the metabolite. The DNA antibodies in this group were also capable of being absorbed by metabolite-HSA as well as hydralazine-HSA, indicative of the cross-reactivity between hydralazine and its metabolite. Immunization with hydralazine-RSA caused rabbits to produce antibodies to hydralazine but not to DNA, indicating the requirement for an immune response to the carrier protein in order for antibodies reactive with DNA to be produced. Thus, hyperimmunization of rabbits with hydralazine-protein conjugates may provide a useful animal model of SLE. The data suggests that an immune response to hydralazine may be important in human hydralazine-induced SLE.

Electrochemistry and detection of some organic and biological molecules at conducting polymer electrodes. Part 3. Evidence of the electrocatalytic effect of the heteroatom of the poly(hetetroarylene) at the electrode/electrolyte interface

Abstract The electrocatalytic effect of the conducting poly(3-methylthiophene) film (3-PMT) electrode on the redox behavior of catechol compounds has been examined. The nature of the electrode material substrate had no effect on the peak potentials in the cyclic voltammograms (CVs) of different redox systems of biological interest: p -aminophenol, dopamine, catechol and ascorbic acid. The nature of the heteroatom of 3-PMT, polypyrrole, polyfuran and polyanaline had a very large effect on their electrokinetic properties. The adsorption of molybdenum ion results in the blocking of ‘the active sites’ at the interface, as indicated by the disappearance of the electrochemical activity of the 3-PMT film electrode. The surface examination by X-ray photoelectron spectroscopy (XPS) of the molybdenum exposed polymer suggests the possibility of a chemical bonding between the metal ions and the sulfur heteroatom of the polymer surface. The ‘apparent’ diffusion coefficients D app were determined from the effect of the scan rate dependency of CVs of the catechol, etc. The results showed that the electron transfer is predominantly diffusion controlled at the polymer/vbsolution interface and probably involves the sulfur heteroatom specifically.

Voltammetric studies of the oxidation of reduced nicotinamide adenine dinucleotide at a conducting polymer electrode

Voltammetric studies of the redox behaviour of NADH at a poly(3-methylthiophene) conducting polymer electrode showed a large electrocatalytic effect without the use of electron-transfer mediators.

α-Heterosubstituted phosphonate carbanions IX: diethyl 1-phenyl-1-trimethylsiloxymethane phosphonate as an acyl anion equivalent; A novel method for the preparation of α-hydroxyketones.

Abstract Diethyl 1-phenyl-1-trimethylsiloxymethane phosphonate carbanion was found to react as an effective acyl anion equivalent in the preparation of α-hydroxy ketones from aliphatic and aromatic aldehydes and ketones. A 1,4-oxygen-oxygen silicon migration was also observed.

Synthesis of 8-Substituted Xanthines and Their Oxidative Skeleton Rearrangement to 1-Oxo-2,4,7,9-tetraazaspiro[4,5]dec-2-ene-6,8,10-triones

The synthesis of a number of 8-(dialkylamino)- and 8-alkoxyxanthines (3 and 6, respectively) is described. Treatment of 3 with m-chloroperoxybenzoic acid (m-CPBA) gave by a novel rearrangement 3-(disubstituted amino)-4,7,9-trimethyl-1-oxo-2,4,7,9-tetraazaspiro[4,5]dec-2-ene-6,8,10-triones 10. Also, the corresponding 3-alkoxy-subtituted spiro compounds 12 were obtained by an analogus treatment of 8-alkoxyxanthines 6. In attempts to elucidate a tentative mechanism for this rearrangement 8-[(dialkylamino)methyl]caffeines 7 when treated with m-CPBA did not undergo the rearrangement but only yielded the expected N-oxide derivatives 16. This result seems to indicate that a necessary structure element for this rearrangement to occur is an atom with an unshared pair of electrons to be attached to the 8-position of the investigated xanthines. In agreement with this statement is the fact that N-oxides of 8-[(dialkylamino)methyl]caffeines 16 do not undergo the novel rearrangement but rather give the expected Meisenheimer rearrangement or the Cope elimination depending upon reaction conditions.

Prospective study of immunologic effects of hydralazine in hypertensive patients

Twenty‐seven hypertensive patients (23 of whom were black) were treated with hydralazine as their major antihypertensive drug and were followed for evidence of autoimmunity and clinical systemic lupus erythematosus (SLE). Only one patient developed SLE but many, although asymptomatic, had serologic evidence of autoimmunity: antibodies to single‐ and double‐stranded ribonucleic acid (RNA), single‐stranded deoxyribonucleic acid (DNA), histones, and lymphocytes. Acetylation phenotype profoundly influenced this response; slow acetylators had a higher incidence and larger amounts of autoantibodies. Antibodies to both types of RNA were a more sensitive index of autoimmunity than antinuclear antibodies. Hydralazine treatment did not alter cell‐mediated immune responses. The hydralazine SLE patient had large amounts of autoantibodies that were predominantly IgG, while in the others IgM autoantibodies were predominant. No antibodies, but positive lymphoproliferative responses to hydralazine, were found in half the patients tested.