Liquid phase hydrogenation and hydrodenitrogenation of aromatic nitrogen-containing environmental pollutants

Carcinogenic aromatic nitro-compounds are hydrogenated at 80–140 °C in the presence of a silica sol–gel entrapped combined palladium-[Rh(cod)Cl]₂ catalyst to give hydroaromatic amines and nitrogen-free hydrocarbons. The process involves initial transformation of the nitro to an amino function. Further hydrogenation causes denitrogenation and saturation of the aromatic moieties. Using 1-aminonaphthalene as a model substrate reveals simultaneous formation of 1- and 5-aminotetralin. While the former amine is readily converted into tetralin and 1-aminodecalins, the 5-aminotetralin gives, in a slow process, only the aminodecalins. The latter compounds are slowly denitrogenated to decalins. The catalytic hydrogenation of the aromatic compounds is accompanied by NH₃ elimination by which secondary amines are formed in a reversible fashion. The entrapped catalyst is leach-proof and recyclable. However, its catalytic activity in the different steps changes during the recycling. The high activity of the combined catalyst results from synergism between the two different metal nuclei.     

Rose bengal dye on thiol-terminated bilayer for molecular devices

Recently, it has become increasingly important to control molecular layers, especially with regard to the formation of bilayers, in order to avoid electrical shorts in molecular electronics. In this paper, we report on the characterization of an in situ thiol-terminated bilayer that is formed by hydrogen bonding between the amine group of an aminoalkanethiol monolayer on a gold surface and the free amine group of aminoalkanethiolates in a bulk solution. We also report on the use of a rose bengal (RB) monolayer on a thiol-terminated bilayer for the purpose of application in a molecular memory device. Using surface-sensitive techniques such as grazing angle Fourier transform infrared (FT-IR) spectroscopy, quartz crystal microbalance (QCM) measurement, ellipsometry, X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV), we characterized a thiol-terminated bilayer (TUA-AUT) and an RB functionalized monolayer on a bilayered surface (RB-TUA-AUT). For a control experiment, we prepared a single RB monolayer attached by an ethanethiol group to a gold surface. In order to assess the feasibility of the present approach with respect to application in molecular electronics, we tested the switching property of the self-assembled monolayers (SAMs) using conducting-probe atomic force microscopy (CP-AFM). The RB monolayer on the bilayered surface exhibited hysteresis, while a single RB monolayer gave an electrical short.     

Synthesis of threitol ceramide and [14C]threitol ceramide,non-glycosidic analogues of the potent CD1d antigen α-galactosyl ceramide

The synthesis of threitol ceramide, which is a non-glycosidic analogue of the potent CD1d antigen α-galactosyl ceramide, is described. The synthesis of a ¹⁴C-labelled threitol ceramide analogue is also presented. This radiolabelled analogue will allow the intracellular trafficking pattern/itinerary of this iNKT-CD1d cell agonist to be studied.     

The reaction of bicyclic phosphine oxides,containing a hindered double bond with m-chloroperbenzoic acid

The reaction between m-chloroperbenzoic acid and phosphabicyclic phosphine oxides (e.g. 8-phenyl-8-oxo-8-phosphabicyclo[3.2.1]oct-6-ene) was investigated and the structure and stereochemistry of the compounds elucidated. It could be shown that compounds possessing the allyl-P(O) R(or Ar) site, in which the double bond is hindered enough to prevent a usual epoxidation, are oxidised by the peracid to the corresponding phosphinate. Furthermore, when the resulting compounds are still strained the phospinates are unstable. The suggested mechanism for the oxidation is a process similar to the Bayer-Villiger oxidation, which is known for ketones.     

N-acyl-2-methylene-β-alanine methyl esters from the sponge Fasciospongia cavernosa

The isolation and structural determination of a series of N-acylated 2-methylene-β-alanine methyl esters, a new naturally-occurring β-amino acid, from the sponge Fasciospongia cavernosa, is reported.     

Hydroxide ion initiated reactions under phase transfer catalysis conditions—IV : Effect of catalyst structure

The nature of the quat-anion interactions in a PTC/OH^? system was probed by examining the reactivity and selectivity of a CA/O-ambident anion towards an alkylating agent in the presence of various quats. It is suggested that the accessibility of the positive N center of the qual for association with the anion is the major factor in determining the behavior of PTC/OH^? reactions proceeding through the Makosza mechanism.     

8-phosphabicyclo[3.2.1]octanes—II: The synthesis and stereochemistry of 8-phosphabicyclo[3.2.1]oct-6-enes

Several new 8-phosphabicyclo[3.2.1]oct-6-enes and -6-en-3-yl acetates were prepared by the alkyl (or aryl)dihalophosphane addition to cyclohepta -1,3-diene and 1-acetoxy cyclohepta-3,5-diene. The P-configuration in two P-epimer pairs (3, 4 and 5, 6) and three other compounds which were each obtained as a single isomer (1, 2 and 7) was determined by investigation of the NMR spectra, i.e. by complexation of the compounds with Eu(dpm)₃ as well as from the various phosphorus-hydrogen coupling constants. Compounds possessing the same P-substituent were correlated among themselves and in the case of the PPh bearing compounds (1 and 7) further correlation to a known compound (8a) was established. The chemical behaviour of the C₆C₇ double bond is discussed and compared with the corresponding behaviour in trop-6-enes. Great steric hindrance was found for this bond, for which the following sequence is suggested:

The synthesis of a phosphaatropine analog is described.     

Cutoff solitons in axially uniform systems

The optical response of axially uniform nonlinear photonic bandgap fibers is studied theoretically. We observe gap-soliton-like generation and associated bistability, similar to what is typically found in periodically modulated nonlinear structures. This response stems from the nature of the guided-mode dispersion relations, which involve a frequency cutoff at zero wave vector. In such systems, solutions with zero group velocities and minimal coupling to radiation modes come in naturally. We term such solitons "cutoff solitons"; they provide an interesting alternative to gap solitons in periodically index-modulated fibers for in-fiber all-optical signal processing.