The Pt-catalyzed carboselenation of alkynes by selenoesters

[reaction: see text] The Pt-catalyzed carboselenation of terminal alkynes with selenoesters provided vinylselenides regio- and stereoselectively in moderate yields.     

Nickel‐Catalyzed Dimerization and Alkylarylation of 1,3‐Dienes with Alkyl Fluorides and Aryl Grignard Reagents

In the presence of a nickel catalyst, 1,3‐butadiene undergoes selective dimerization and alkylarylation with alkyl fluorides and aryl Grignard reagents to give 1,6‐octadienes with alkyl and aryl groups at the 3‐ and 8‐positions, respectively, by the consecutive formation of three carbon–carbon bonds. The formation of an anionic nickel complex plays an important role in forming C?C bonds with alkyl fluorides.     

Experimental study on forced convective heat transfer of flowing gaseous solid suspension at high temperature

The results of an experimental study of the forced convective heat transfer to helium-graphite suspension at high temperatures up to 1173K are presented. Entering gas Reynolds number ranges from 1.0 x 10⁴ to 2.0 x 10⁴ and the particle loading ratio reaches about 4. The ratio of the Nusselt number of the suspension to that of gas alone increases considerably in a range of high loading ratios as the wall temperature increases. Subsequently, two kinds of turbulence promoters (200 and 400 mm pitch twisted tapes) are inserted in the flowing gaseous solid suspensions to make use of the large inertia forces of particles. The current results show that the local heat fluxes with use of the tapes increase significantly with the rise in the wall temperature owing to the radiative effect of the particulate phase.     

Negative normal restitution coefficient found in simulation of nanocluster collisions

The oblique impacts of nanoclusters are studied theoretically and by means of molecular dynamics. In simulations we explore two models--Lennard-Jones clusters and particles with covalently bonded atoms. In contrast with the case of macroscopic bodies, the standard definition of the normal restitution coefficient yields for this coefficient negative values for oblique collisions of nanoclusters. We explain this effect and propose a proper definition of the restitution coefficient which is always positive. We develop a theory of an oblique impact based on a continuum model of particles. A surprisingly good agreement between the macroscopic theory and simulations leads to the conclusion that macroscopic concepts of elasticity, bulk viscosity, and surface tension remain valid for nanoparticles of a few hundred atoms.     

Ni- or Cu-catalyzed cross-coupling reaction of alkyl fluorides with Grignard reagents

n-Octyl fluoride underwent a cross-coupling reaction with n-propylmagnesium bromide in the presence of 1,3-butadiene using NiCl2 as a catalyst at room temperature to give undecane in moderate yields. This alkyl-alkyl cross-coupling proceeded more efficiently when CuCl2 was employed instead of NiCl2. Addition of 1,3-butadiene dramatically improved the yields of the coupling products from primary alkyl Grignard reagents in both Ni- and Cu-catalyzed reactions. Alkyl fluorides efficiently reacted with tertiary alkyl and phenyl Grignard reagents using CuCl2 in the absence of 1,3-butadiene to afford the coupling products in high yields. The competitive reaction of a mixture of alkyl halides (R-X; X = F, Cl, Br) with nC5H11MgBr showed that the reactivities of the halides increase in the order R-Cl < R-F < R-Br. In contrast, in the Cu-catalyzed reaction with PhMgBr, the reactivities increase in the order R-Cl < R-Br < R-F.