Enantioselective Borylation of Aromatic C-H Bonds with Chiral Dinitrogen Ligands.

The borylation of C-H bonds catalyzed by transition metals has been investigated extensively in the past two decades, but no iridium-catalyzed enantioselective borylation of C-H bonds has been reported. We report a set of iridium-catalyzed enantioselective borylations of aromatic C-H bonds. This reaction relies on a set of newly developed chiral quinolyl oxazoline ligands. This process proceeds under mild conditions with good to excellent enantioselectivity, and the borylated products can be converted to enantioenriched derivatives containing new C-O, C-C, C-Cl, or C-Br bonds.

A Chiral Nitrogen Ligand for Enantioselective, Iridium-Catalyzed Silylation of Aromatic C-H Bonds.

Iridium catalysts containing dative nitrogen ligands are highly active for the borylation and silylation of C-H bonds, but chiral analogs of these catalysts for enantioselective silylation reactions have not been developed. We report a new chiral pyridinyloxazoline ligand for enantioselective, intramolecular silylation of symmetrical diarylmethoxy diethylsilanes. Regioselective and enantioselective silylation of unsymmetrical substrates was also achieved in the presence of this newly developed system. Preliminary mechanistic studies imply that C-H bond cleavage is irreversible, but not the rate-determining step.

Theoretical investigation on the reaction of adhesion unit dopa in mussel with electrolyzing seawater.

Adhesive proteins secreted by the marine mussel could bind strongly to all kinds of surfaces, for instance, ship hulls and petroleum pipelines. Studies indicated that there was an unusual amino acid 3,4-dihydroxy-l-phenylanine (dopa), which was the crucial super adhesive unit in the proteins. The technology of electrolyzing seawater was employed to generate HOCl solution to hinder the adhesion. However, the detailed anti-fouling mechanism of HOCl solution remained unknown to be fully explained. Herein, we theoretically reported a study of single molecular (dopa) reaction under the HOCl solution environment, which would be helpful to reveal the anti-fouling mechanism through electrolyzing seawater. By using the density functional theory (DFT) quantum mechanics procedure, we theoretically studied the reaction mechanism of the adhesive unit dopa in mussel with electrolyzing seawater. Two possible pathways (1 and 2) were obtained (Fig. 6). The transition state for each pathway was determined, the intrinsic reaction coordinate (IRC) was analyzed and the mechanism had been confirmed. The calculations indicated dopa tended to have electrophonic attacking substitution reaction to generate 3-chlorine-4,5-dihydroxyphenylalanine (dopa-Cl) with different pathways, which hindered the formulation of conjuncted dopa-dopa and thus the stickiness among mussel adhesive proteins reduced. The transition states computation showed that pathway (1) had one transition state (TS1-1) with an activation energy of 102.22 kJ mol(-1), while pathway (2) had two transition states (TS2-1, TS2-2) with activation energies of 191.98 kJ mol(-1) and 42.00 kJ mol(-1) respectively and one intermediate (IM2-1). Rate constant value of pathway (1) was much bigger than that of pathway (2) regardless of high or low temperature, which meant that in the reaction process, pathway (1) was the favorable reaction step; but as the temperature rose, the competitiveness of pathway (2) gradually increased. After the theoretical calculation, we found that it was Cl(+) played an important and direct role in the dopa's modification.