Ylide Chemistry: An Account of Structural,Conformational and Redox Investigations

Abstract

Structural data of phosphorus ylides are summarized and discussed. Conformational preferences in solution and in the solid state, as followed by NMR spectroscopy and X-ray diffraction, indicate a strong gauche effect for the lone pairs of electrons at the ylidic carbon atom. One- and two-electron oxydation of ylide carbanions is accomplished with copper(II) as the oxidant, leading to oxidative coupling or to halogenation, respectively.     

Novel Dithiolene Complexes and Tetrathiafulvalenes

Abstract

Novel dithiolene metal complexes, some of which absorb in the near infrared, and tetrathiafulvalenes, in particular tetraiodotetrathia- fulvalene, have been prepared, and their magnetic properties studied.     

Influence of the Metal Ion on the Two‐Photon Absorption Properties of Lanthanide Complexes Including Near‐IR Emitters

The synthesis of tris(2‐thenoyltrifluoroacetonate)lanthanide(III) complexes featuring a diethylaminostyryl‐2,2′‐bipyridine coligand was achieved for lanthanum; the near‐infrared (NIR) emitters neodymium, erbium, and ytterbium; and the transition‐metal yttrium. The photophysical properties were thoroughly studied, and it was demonstrated that the conjugated bipyridine ligand acts as a good antenna for the sensitization of the NIR emitters. The two‐photon absorption (TPA) properties of all five complexes were investigated by using both two‐photon excited fluorescence and the Z‐scan method. We demonstrate that the nature of the rare earth ion has almost no influence on the TPA properties centered on the conjugated bipyridyl ligand. Finally, we show that Yb^III is sensitized by a two‐photon antenna effect, and that Nd^III is mostly sensitized by a one‐photon process involving direct excitation of forbidden f–f transitions.     

Detection, quantification, and identification of dermorphin in equine plasma and urine by LC–MS/MS for doping control

Dermorphin is a unique opioid peptide that is 30–40 times more potent than morphine. It was misused and went undetected in horse racing until 2011 when intelligence obtained from a few North American race tracks suggested its use. To prevent such misuse, a reliable analytical method became necessary for detection and identification of dermorphin in post-race horse samples. This paper describes the first liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for such a purpose. Equine plasma and urine samples were pre-treated with ethylenediamine tetra-acetic acid and urea prior to solid-phase extraction (SPE) on Oasis MCX cartridges. Resulting eluates were dried under vacuum and analyzed by LC–MS/MS for dermorphin. The matrix effect, SPE efficiency, intra-day and inter-day accuracy and precision, and stability of the analyte were assessed. The limit of detection was 10 pg/mL in plasma and 20 pg/mL in urine, and the limit of confirmation was 20 pg/mL in plasma and 50 pg/mL in urine. Dermorphin in plasma is stable at ambient temperature, but its diastereomer is unstable. With isotopically labeled dermorphin as an internal standard, the quantification range was 20–10,000 pg/mL in plasma and 50–20,000 pg/mL in urine. The intra-day and inter-day accuracy was from 91 % to 100 % for the low, intermediate, and high concentrations. The intra-day and inter-day coefficients of variation were less than 12 %. The method differentiates dermorphin from its diastereomer. This method is very specific for identification of dermorphin in equine plasma and urine, as assessed by BLAST search and targeted SEQUEST search, and by MS/MS spectrum library search. The method has been successfully applied to analysis of samples collected following dermorphin administration to research horses and of official post-race samples.

Compressed matrix thin film (CMTF)-assisted laser desorption ionization mass spectrometric analysis

The inhomogeneous re-crystallization process of matrix materials is the major concerns associated with matrix assisted laser desorption/ionization (MALDI) analysis. We describe here the approach termed compressed matrix thin film (CMTF) in order to make a uniform matrix deposition. In this approach, solid matrix particles are compressed under 10 MPa of pressure by a compressor that is regularly used in infrared spectroscopic analysis. Then aqueous samples can be deposited on the surface of the matrix film. Major advantages of the CMTF approach are summarized as follows. (1) Reproducible sample preparation procedure. Size and thickness of matrix thin films can be controlled by using a fixed mold.force and known amount of matrix materials. (2) Significantly decreased shot-to-shot variations and enhanced reproducibility. (3) Tolerance for in situ salt washing. Because matrix materials are hydrophobic, salts can be washed away while proteins or peptides are retained on the surface of matrix thin films through hydrophobic interactions. (4) Improved sensitivity. The hydrophobic coating of MALDI sample plate by matrix thin films prevents the spreading of samples across the plate and confines analytes to a small area, leading to increased local concentration. (5) A new means for tissue analysis. Tissue sections can be directly transferred to the uniform surface of matrix materials for reproducible and quantitative comparison of different molecules in different localization. The proposed CMTF should be an enabling technique for mass spectrometric analysis with improved correlations between signal intensities and sample quantities.     

Catalytic Oxidative Domino Degradation of Alkyl Phenols Towards 2- and 3-Substituted Muconolactones

The catalytic oxidative domino degradation of phenols was investigated. Hydrogen peroxide (30% aq.) was used as an oxidant and 2,2′-dinitro-4,4′-ditrifluoromethyldiphenyl diselenide 4e as a catalyst. The products were muconic acid 5, and muconolactones muconolactones—5-carboxymethylfuran-2(5H)-ones 7 and 9. Phenols with alkyl groups at 2 or 4 positions of the benzene ring were converted regioselectively to corresponding muconolactones substituted at alkenylene ring carbon atoms. The reaction mechanism is proposed.     

Improved Synthesis of the ORL Antagonist 1-[(3R,4R)-1-Cyclooctylmethyl-3-ethoxycarbonyl-4-piperidinyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one (J-113397)

A practical synthesis of optically pure 1-[(3R,4R)-1-cyclooctylmethyl-3-ethoxycarbonyl-4-piperidinyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one (J-113397) was developed that avoids the use of chiral columns.     

Investigation of steric and electronic effects in the copper-catalysed asymmetric oxidation of sulfides

Steric and electronic effects in the copper-catalysed asymmetric oxidation of aryl benzyl, aryl alkyl and alkyl benzyl sulfides have been investigated. The presence of an aryl group directly attached to the sulfur is essential to afford sulfoxides with high enantioselectivities, with up to 97% ee for 2-naphthyl benzyl sulfoxide, the highest enantioselectivity achieved to date for copper-catalysed asymmetric sulfoxidation. In contrast, the benzyl substituent can be replaced by sterically comparable groups with no effect on enantioselectivity. Copper-mediated oxidation of substituted aryl benzyl sulfides display modest steric and electronic effects resulting in comparable or lower enantioselectivities to those obtained with the unsubstituted benzyl phenyl sulfide.