Sequential Ugi/Heck cyclization strategies for the facile construction of highly functionalized N-heterocyclic scaffolds

A new strategy employing an Ugi four-component reaction and a microwave-assisted intramolecular Heck cyclization in a sequential fashion to access an array of N-containing heterocycles is reported. The two-step sequence generated compounds of significant molecular complexity from trivial starting materials in an expedient fashion with excellent yields. The route was also amenable to solid-phase chemistry demonstrating potential for library generation.     

Flow-induced nonequilibrium thermodynamics of lamellar semicrystalline polymers

In this work we present a first attempt to quantify the effect of flow deformation on the microstructure of semicrystalline polymers. This necessitates bridging the macroscopic flow length scale with the microscopic (segment) length scale of the semicrystalline structure. To achieve this connection we developed a hierarchical approach where a thermodynamically consistent macroscopic constitutive equation is interfaced with a microscopic lattice-based Monte Carlo (MC) simulation of the polymer chain conformation. We first illustrate this approach in a two-dimensional (2D) “toy” application where the 2D equivalent of a macroscopic constitutive equation based on reptation theory is applied to describe the chain deformation and extended free energy in the amorphous bulk phase. The values for the derivative of the free energy with respect to the mean segment orientation tensor, calculated for a planar extensional flow, are then used as an extended nonequilibrium thermodynamic forcing term. This is added in a traditional Metropolis Monte Carlo scheme, developed for a 2D lattice representation of a lamellar semicrystalline polymer, to drive the flow-induced microstructure. Significant flow-induced changes are calculated, steadily increasing as the Weissenberg number increases.We subsequently extend these ideas further in a much more realistic three-dimensional (3D) application where the information for the thermodynamics of the bulk amorphous phase under a uniaxial extensional flow is extracted from a macroscopic network model, such as that of Phan-Thien and Tanner (PTT), connecting the free energy to the second moment of the end-to-end distance of a multisegment chain. Through a series of 3D nonequilibrium Monte Carlo simulations of both the amorphous and the semicrystalline microscopic morphologies, it is shown that the interaction of the flow-induced deformation with the semicrystalline microstructure is nonlinear: the amorphous interlamellar structure changes significantly from its corresponding homogeneous bulk amorphous state, even far away from the crystalline interface. Our approach allows for a quantitative estimation of this effect on both thermodynamic quantities, like the extended microscopic free energy, as well as various statistics of the chain conformations.     

Regularity of Intermittent Bursts in BriggsRauscher Oscillating Systems with Phenol

The intermittency or intermittent bursting as the type of dynamic state when two qualitatively different behaviors replace one another randomly during the course of the reaction, although all the control parameters remain constant, is found in the Briggs? Rauscher oscillating system moderated by a very small amount of phenol. Within a range of phenol concentrations, the oscillation amplitude is diminished considerably, and after oscillations cease, they repeat intermittently, giving several bursts of oscillations. For the concentrations used here, the range of phenol concentrations where intermittent bursting oscillations occur in a closed reactor is ca. 1.8×10^?5 to 3.6×10^?5 M . Bursting also occurs in an open reactor and can be sustained indefinitely at 5.53×10^?5 M concentration. The intermittent bursting behavior is robust, and can be achieved at a variety of conditions.     

Multiresolution expansion, approximation order and quasiasymptotic behavior of tempered distributions

Multiresolution analysis of tempered distributions is studied through multiresolution analysis on the corresponding test function spaces Sr(R), r∈N₀. For a function h, which is smooth enough and of appropriate decay, it is shown that the derivatives of its projections to the corresponding spaces Vj, j∈Z, in a regular multiresolution analysis of L²(R), denoted by hj, multiplied by a polynomial weight converge in sup norm, i.e., hj→h in Sr(R) as j→∞. Analogous result for tempered distributions is obtained by duality arguments. The analysis of the approximation order of the projection operator within the framework of the theory of shift-invariant spaces gives a further refinement of the results. The order of approximation is measured with respect to the corresponding space of test functions. As an application, we give Abelian and Tauberian type theorems concerning the quasiasymptotic behavior of a tempered distribution at infinity.     

Efficient Pd-catalyzed synthesis of 2-arylaminopyrimidines via microwave irradiation

An efficient method for the synthesis of 2-arylaminopyrimidines via microwave assisted, Pd-mediated amination of 2-chloropyrimidine is reported. This method is superior to the classical heating process, particularly when one of starting materials is a heteroarylamine.     

An initial value problem arising in mechanics

We study an initial value problem for a system consisting of an integer order and a distributed-order fractional differential equation describing forced oscillations of a body attached to a free end of a light viscoelastic rod. An explicit form of a solution for a class of linear viscoelastic solids is given in terms of a convolution integral. Restrictions on storage and loss moduli following from the second law of thermodynamics play the crucial role in establishing the form of the solution. Some previous results are shown to be special cases of the present analysis.     

New Drimane Sesquiterpenoids from Tidestromia oblongifolia

From an acetone extract of the aerial parts of Tidestromia oblongifolia (Amaranthaceae), a new drimane sesquiterpenoid bearing an 11,12,13-trihydroxydrimene skeleton (1) as well as the 11,12 acetonide of 1 were isolated. Three known stigmastane triterpenoids were also isolated. Structures were elucidated with the aid of 1D and 2D NMR spectroscopic techniques. The absolute configuration of 1 was confirmed by single-crystal x-ray crystallography. This is the first report on phytochemical constituents from any plant of the genus Tidestromia and is the first report of the occurrence of drimanes in the Amaranthaceae.     

Global convoluted semigroups

Global exponentially bounded convoluted semigroups in Banach spaces are systematically treated with the help of Laplace transform. A perturbation theorem in this context is proved and some characterizations of the introduced class of analytic convoluted semigroups are obtained. Illustrative examples of generators of convoluted semigroups, including differential operators, are presented. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)