Isopropanol Dehydration on Amorphous Silica-Alumina: Synergy of Brønsted and Lewis Acidities at Pseudo-Bridging Silanols.

The mechanism of isopropanol dehydration on amorphous silica-alumina (ASA) was unraveled by a combination of experimental kinetic measurements and periodic density functional theory (DFT) calculations. We show that pseudo-bridging silanols (PBS-Al) are the most likely active sites owing to the synergy between the Brønsted and Lewis acidic properties of these sites, which facilitates the activation of alcohol hydroxy groups as leaving groups. Isopropanol dehydration was used to specifically investigate these PBS-Al sites, whose density was estimated to be about 10-1  site nm-2 on the silica-doped alumina surface under investigation, by combining information from experiments and theoretical calculations.

PtCl 2-catalyzed cycloisomerizations of allenynes.

The PtCl2-catalyzed cycloisomerization of allenyne systems has been examined. This process is a highly versatile tool for obtaining products that cannot be attainable with other metals. Simple adjustment of the allene or alkyne substitution can direct the reactivity in a selective manner and give birth to important carbocyclic frameworks (hydrindenes, cyclic vinylallenes, and trienes).