Control of selectivity in the preparation of 2-substituted benzoazoles by adjusting the surface hydrophobicity in two solid-based sulfonic acid catalysts.

A series of metal-free tandem reactions for the synthesis of pharmaceutically important 2-substituted benzoazoles from isothiocyanates and 2-aminothiophenol under catalyst-free conditions in the presence of Et-PMO-Me-PrSO3H (1a) and SBA-15-PrSO3H (1b) as solid acids were carried out in a highly selective way under solvent free conditions. A significant selectivity changeover toward either 2-mercaptobenzoxazole or 2-aminobenzoazole derivatives could be achieved by changing the employed catalyst from the relatively hydrophobic material 1a to the more hydrophilic catalyst 1b. This simple experimental procedure with a novel selective approach toward benzoazoles accompanied by green and reusable catalysts could be considered as an alternative to the existing methods for the synthesis of 2-substituted benzoazole derivatives.

Hydrodynamic volume of trehalose and its water uptake mechanism.

Trehalose ability to preserve water in biology has spawned research on this special disaccharide and its solutions. Trehalose unlike any other disaccharide, tend to mix with almost any amount of water. In water, Trehalose forms a hydrodynamic volume with bound waters (both coordination water and semicircular heterogeneities), capable of perturbing the very nature of normal bulk water. Switching of the two major conformational forms, defined by their helicities (i, i-H2O with lower helicity and ii, ii-H2O with higher helicity), were closely examined, using DFT/B3LYP- 6-311 + G** level of theory, along with molecular dynamic (MD) calculations in aqueous media. Patterns in radial distribution functions (RDF) confirmed semicircular heterogeneities, including spines of water (rows of slow water molecules), in Trehalose hydration shell. Dynamics of Trehalose conformational switch and its coordination water are coupled to dynamics of these spines of water, which are themselves coupled to dynamics of the rest of Trehalose hydration shell waters. Like seamless cogwheels such energy cascade links the upstream slow dynamics of spines to the downstream collective bulk water dynamics. This lubricates Trehalose conformational switch through coordination water uptake, for which we proposed a mechanism here. We show how the coupling between Trehalose and bound waters in its hydrodynamic volume encompass both function and dynamic of the molecule and its hydration shell. Further simulations are needed to see how this ability is related to the evading and percolating nature of cryoprotectant water, also reported for the self-coordinating jelly behavior of biological water.

Magnetic solid sulfonic acid decorated with hydrophobic regulators: a combinatorial and magnetically separable catalyst for the synthesis of α-aminonitriles.

A three-component, Strecker reaction of a series of aldehydes or ketones, amines, and trimethylsilyl cyanide for the synthesis of α-aminonitriles in the presence of a catalytic amount of a magnetic solid sulfonic acid catalyst, Fe3O4@SiO2@Me&Et-PhSO3H under solvent-free conditions have been investigated. This catalyst, with a combination of hydrophobicity and acidity on the Fe3O4@SiO2 core-shell of the magnetic nanobeads, as well as its water-resistant property, enabled easy mass transfer and catalytic activity in the Strecker reaction. The catalyst was easily separated by an external magnet and the recovered catalyst was reused in 6 successive reaction cycles without any significant loss of activity.