Palladium-catalyzed alkoxycarbonylation of (Z)-2-en-4-yn carbonates leading to 2,3,5-trienoates

Pd(0)-catalyzed carbonylation of (Z)-2-en-4-yn carbonates in the presence of a balloon pressure of CO in an alcohol donates vinylallenyl esters with an exclusively E-configuration and in high yields. The fact that no such reactivity could be observed with E-configured enyne carbonates may indicate that the reaction is promoted via the cooperative coordination of palladium with both alkynyl and carbonate moieties.     

Isolable, gold carbonyl complexes supported by N-heterocyclic carbenes

Cationic gold carbonyl complexes supported by N-heterocyclic carbene ligands, SIDipp and IDipp, have been synthesized. [(SIDipp)Au(CO)][SbF(6)] has a linear, two-coordinate gold center. [(SIDipp)Au(CO)][SbF(6)] and [(IDipp)Au(CO)][SbF(6)] display ?ν(CO) values at 2197 and 2193 cm(-1), respectively. Computational studies on [(SIMe)Au(CO)](+) indicate the presence of a strong Au(I)-CO bond.     

Supports of Weighted Equilibrium Measures and Examples

We analyze the supports of weighted equilibrium measures in ? ⁿ . We give explicit examples of families of compact sets which arise as the support of a weighted equilibrium measure for some admissible weight w. These examples also give new constructions of plurisubharmonic functions in the Lelong class. We also include a list of open problems on the support of extremal measures which are related to solutions of Monge–Ampère equations.     

Evaluating Mohr–Coulomb yield criterion for plastic flow in model metallic glasses

The yielding of metallic glasses (MGs) is generally considered to be dependent on pressure or normal stress, which is usually described by the Mohr–Coulomb yield criterion. Experimentally, the orientation of the shear band angle or fracture angles in MG is roughly 40° to 42° in uniaxial compression and 50° to 59° in uniaxial tension, both with respect to the loading direction. However, the amounts of deviation from the maximum shear stress direction (45°) under uniaxial tension and compression are quite different, which seems to be inconsistent with the Mohr–Coulomb yield criterion. Here we carried out molecular dynamics simulations to study the incipient plasticity of model Dzugutov glasses subjected to various uniaxial and biaxial stress states. The yield points are defined as the sharp rise of the population of atoms participating in non-affine deformations, in addition to the traditional offset method. The yield surfaces thus created agree well with the Mohr–Coulomb yield criterion. Furthermore, the orientations of the embryonic shear bands (instead of the fully-grown shear bands, or fracture planes) are measured, which also follow predictions based on the Mohr–Coulomb criterion. Our simulation results call for orientational measurement of incipient shear bands in experiments to critically examine the Mohr–Coulomb yield criterion in MG systems.     

Total synthesis of 7'-desmethylkealiiquinone

The total synthesis of an analogue of the marine alkaloid kealiiquinone has been completed through application of an intramolecular Diels-Alder reaction of an imidazole-containing enyne. Oxidative aromatization of the lactone adduct and N-methylation facilitates C2-oxidation via the imidazolium salt. Conversion of the lactone to the phthalaldehyde derivative and then to the dihydroxybenzoquinone was achieved via a reaction with glyoxal in the presence of KCN. Esterification of the vinylogous diacid and deprotection provided 7'-desmethylkealiiquinone.     

Refraction losses in terahertz computed tomography

Terahertz pulsed imaging has been used to perform computed tomography of three-dimensional objects inducing high refraction losses. We were able to obtain cross-sectional images of the targets by using a computed tomographic analysis of the terahertz signal based on a multi-peak averaging procedure. Some examples are presented of objects with complex shape such as a Teflon cylinder and a dried chicken bone.