Synthesis and Photochemistry of Novel 3,5-Diacetyl-1,4-dihydropyridines

 Some novel 3,5-diacetyl-1,4-dihydropyridine derivatives were synthesized; their photochemical behaviour was studied under oxygen or argon atmosphere. Irradiation of these compounds resulted in the aromatization of the ring and formation of 3,5-diacetylpyridine derivatives. The presence of oxygen plays an important role in the type, rate, or failure of oxidation. Irradiation of these compounds with of 2-furyl or 5-methyl-2-furyl substituents in position 4 under argon resulted in the formation of a pyridine ring with retention of these substituents, whereas loss of these substituents and ring aromatization was observed upon irradiation under oxygen.     

Note from the Publishers Pyroelectric behavior and dielectric properties of linear copolysiloxane/eicosylamine superlattice by A.R.M. Yusoff and W.H. Abd. Majid

In spite of the precautions taken to check the originality of the articles, it happens, unfortunately that our scientific colleagues' vigilance is sometimes caught up unprepared. Today, it has come to our attention that the following article results from a plagiarism. We apologize to the authors who suffered from it. You will find hereafter a note written by Dr Majid which summarizes the situation.     

Highly Efficient,Four Component,One-pot Synthesis of Tetrasubstituted Imidazoles Using a Catalytic Amount of FeCl<Subscript>3</Subscript> · 6H<Subscript>2</Subscript>O

Summary. An efficient and improved procedure for the synthesis of tetrasubstituted imidazoles by FeCl₃ · 6H₂O catalyzed four-component one-pot synthesis in refluxing ethanol is described.     

Rapid and Efficient Synthesis of Imidazolines and Bisimidazolines Under Microwave and Ultrasonic Irradiation

Small assemblies of 2-imidazolines and bisimidazolines from appropriate nitriles and ethylenediamine with catalytic amounts of P₂S₅ employing a microwave assisted protocol were prepared. Sonication of this system also led to successful synthesis of 2-imidazolines and bisimidazolines. Another advantage of these systems is the ability to carry out large scale reactions.     

Variations in,and Relationships of Surface Area,internal angle of friction and compact diametral fracture strength with degree of compaction

The progress of the compaction process to produce from an assembly of particles a coherent mass can be achieved by the application of shear and normal stress. The achievement of a densified coherent mass necessitates, together with the yielding of material, the movement of particles over and between each other. In uniaxial compaction the angle of internal friction, δ_E, is a projection of the unique critical state line which divides a three dimensional relationship between volume change (V), shear stress (?) and normal stress (σ) into yield domains and surfaces. There is one region for failure and flow (the Hvorslev surface) and another region for failure and consolidation (the Roscoe surface). In this paper the concepts of the Roscoe and Hvorslev surfaces together with the Coulomb yield criterion have been applied to the uniaxial compaction, over a range of compactable stresses, of titanium dioxide (20–2000 kPa). The characteristics of applied and shear stress, angle of internal friction (δ_E), angle of shearing resistance (?) and surface area (S_BET) were measured and correlated with the compaction stress (σ_c) and diametral strength (σ_f) of the compacts to investigate the phenomena of uniaxial compaction.     

Macro-Scale Dynamic Effects in Homogeneous and Heterogeneous Porous Media

It is known that the classical capillary pressure-saturation relationship may be deficient under non-equilibrium conditions when large saturation changes may occur. An extended relationship has been proposed in the literature which correlates the rate of change of saturation to the difference between the phase pressures and the equilibrium capillary pressure. This linear relationship contains a damping coefficient, \tau, that may be a function of saturation. The extended relationship is examined at the macro-scale through simulations using the two-phase simulator MUFTE-UG. In these simulations, it is assumed that the traditional equilibrium relationship between the water saturation and the difference in fluid pressures holds locally. Steady-state and dynamic numerical experiments are performed where a non-wetting phase displaces a wetting phase in homogeneous and heterogeneous domains with varying boundary conditions, domain size, and soil parameters. From these simulations the damping coefficient can be identified as a (non-linear) function of the water saturation. It is shown that the value of increases with an increased domain size and/or with decreased intrinsic permeability. Also, the value of for a domain with a spatially correlated random distribution of intrinsic permeability is compared to a homogeneous domain with equivalent permeability; they are shown to be almost equal.     

Enthalpies of formation of chloride fluorides and of methoxide fluorides of tungsten(VI)

Enthalpies of formation of the tungsten (VI) compounds WF₅Cl, WF₄Cl₂, WF₅(OMe), cis-WF₄(OMe)₂ and cis-WF₂(OMe)₄ are reported. Re-distribution and decomposition reactions in the chloride-fluoride and in the methoxide-fluoride series are discussed in the light of the thermochemical results.     

Measurement of residual stresses by the hole-drilling method: Influences of transverse sensitivity of the gages and relieved-strain coefficients

The general expression of the error due to the transverse sensitivity of the gages and the relieved-strain coefficients, in a determination of residual stresses by the hole-drilling method in thin plates, is given. It has been shown that the transverse sensitivity of the gages can be ignored. A moderate amount of error, however, is introduced in the measurement of residual stresses when the relieved-strain coefficients from methods other than double integration over the area of the grid are used. The error due to the use of improper relieved-strain coefficients from rigorous relationships for calculation of residual stresses has been compared with the same part of the error from nonrigorous relationships. Abandonment of the use of nonrigorous relationships is recommended.     

Sulfamic acid catalyzed solvent-free synthesis of 10-aryl-7,7-dimethyl-6,7,8,10-tetrahydro-9H-[1,3]-dioxolo [4,5- <Emphasis Type="Italic">b</Emphasis>]xanthen-9-ones and 12-aryl-9,9-dimethyl-8,9,10,12-tetrahydro-11H-benzo[<Emphasis Type="Italic">a</Emphasis>]xanthen-11-ones

Three-component one-pot synthesis of some novel 10-aryl-7,7-dimethyl-6,7,8,10-tetrahydro-9H-[1,3]-dioxolo[4,5-b]xanthen-9-ones, which have not been published before, and 12-aryl-9,9-dimethyl-8,9,10,12-tetrahydro-11H-benzo[a]xanthen-11-ones from condensation of 3,4-methylenedioxyphenol or β-naphthol, aldehydes and dimedone under solvent-free conditions at 120 °C is reported.