Synthesis of quinoline and benzo[b]thiophene derivatives by ring annelation of pyridines and thiophenes

Selected ortho-disubstituted pyridines and thiopenes react with Michael acceptors to give functionalized quinolines or benzo[b]thiopenes, respectively.     

Phosphorescence polarisation of aromatic compounds oriented in stretched polyethylene films

Phosphorescence polarisation measurements are reported for a number of planar aromatic compounds in stretched polyethylene. The phosphorescence is to about 80% polarised perpendicular to the molecular plane. In the in-plane intensity second order Herzberg-Teller coupling terms may be at least competitive with three-center ππ spin-orbit integrals, in agreement with suggestions of Friedrich, Metz and Dörr.     

A law of large numbers result for a bifurcating process with an infinite moving average representation

This paper derives a law of large numbers theorem for bifurcating processes defined on a perfect binary tree. This theorem can be viewed as a generalization of some results that have already appeared in the literature. For instance, all that is required of the bifurcating process is an infinite moving average representation with geometrically decaying coefficients and a finite moment assumption. In addition, the summands are assumed to belong to a flexible class of functions that satisfy a generalized Lipschitz type condition. These two criteria allow for an expansive range of applicability. Two examples are given as corollaries to the theorem.     

Carbon-13 spin–lattice relaxation in strongly associated molecules: Carboxylic acids

¹³C spin–lattice relaxation times determined for the protonated carbons of carboxylic acids and methyl esters give indications of solution dimerization with the free acids. Since isopthalic and fumaric acids have two carboxyl functions they are able to polymerize in solution. Unlike the case for molecular aggregation due to weak hydrogen bonding in solution (e.g. alcohols, phenols), the ¹³C T₁ values of mono carboxylic acids are not significantly affected by dilution to c. 10^?2 M. Variable temperature T₁ measurements of both the mono and dibasic acids gave activation energies for molecular reorientation of the order of 2 kcal mol^?1, considerably lower than E_a for hydrogen bonded alcohols and comparable with E_a for the unassociated methyl esters of propionic and benzoic acids.     

On the geometry of the characteristic vector of an lcQS-manifold

We study conditions under which the characteristic vector of a normal lcQS-manifold is a torsion-forming or even a concircular vector field. We prove that the following assertions are equivalent:

• An lcQS-structure is normal, and its characteristic vector is a torsion-forming vector field.
• An lcQS-structure is normal, and its characteristic vector is a concircular vector field.
• An lcQS-structure is locally conformally cosymplectic and has a closed contact form.

     

Base-free anaerobic Cu(II) catalysed aryl-nitrogen bond formations

The coupling of arylboronic acids with imidazole in the presence of binuclear bis-μ-hydroxy copper(II) complexes is reported. The reactions can be performed in air as well as under nitrogen atmosphere. Reactions are carried out at ambient temperature without the need for base. The presence of water is essential for the reaction to proceed. Ligand effects on the yield and selectivity are reported.     

Synthesis of 2-substituted piperazines via direct α-lithiation

A novel efficient synthetic route towards the pharmaceutically relevant 2-substituted piperazine class is described. The key step involves α-lithiation of N-Boc piperazines, followed by reaction with several electrophiles. To obtain high yields, in some cases transmetallation to copper after the lithiation step is required.     

Biodistribution and bioactivity of tetra-pegylated meta-tetra(hydroxyphenyl)chlorin compared to native meta-tetra(hydroxyphenyl)chlorin in a rat liver tumor model

It has been proposed that the construction of a photosensitizer-polymer conjugate would lead to an increased selective retention of the drug in tumor tissue resulting in an enhancement of selective tumor destruction by light in photodynamic therapy. In this study the kinetics of a tetra-pegylated derivative of meta-tetra(hydroxyphenyl)chlorin (mTHPC-PEG) were compared with those of native meta-tetra(hydroxyphenyl)chlorin (mTHPC) in a rat liver tumor model. In addition, the time course of bioactivity of both drugs was studied in normal liver tissue. Pegylation of mTHPC resulted in a two-fold increase in the plasma half-life time, a five-fold decrease in liver uptake and an increase in the tumor selectivity at early time intervals after drug administration. However, although mTHPC concentrations in liver decrease rapidly with time, mTHPC-PEG liver concentrations increased as a function of time. This led to a loss of tumor selectivity at all but the earliest time points, whereas with mTHPC tumor selectivity increased with time. For both drugs the time course of bioactivity in the liver parallels drug concentration levels with extensive necrosis after irradiation of mTHPC-PEG-sensitized liver tissue up to drug-light intervals of 120 h. It is concluded that on balance mTHPC-PEG does not appear to show any benefits over native mTHPC for the treatment of liver tumors, as normal liver tissue accumulates the compound. However, pegylation is a potentially promising strategy with an increase in tumor selectivity and reduced liver uptake if accumulation in the liver can be prevented.