Catalytic atroposelective synthesis of axially chiral benzonitriles via chirality control during bond dissociation and CN group formation

The applications of axially chiral benzonitriles and their derivatives remain mostly unexplored due to their synthetic difficulties. Here we disclose an unusual strategy for atroposelective access to benzonitriles via formation of the nitrile unit on biaryl scaffolds pre-installed with stereogenic axes in racemic forms. Our method starts with racemic 2-arylbenzaldehydes and sulfonamides as the substrates and N-heterocyclic carbenes as the organocatalysts to afford axially chiral benzonitriles in good to excellent yields and enantioselectivities. DFT calculations suggest that the loss of p-toluenesulfinate group is both the rate-determining and stereo-determining step. The axial chirality is controlled during the bond dissociation and CN group formation. The reaction features a dynamic kinetic resolution process modulated by both covalent and non-covalent catalytic interactions. The axially chiral benzonitriles from our method can be easily converted to a large set of functional molecules that show promising catalytic activities for chemical syntheses and anti-bacterial activities for plant protections.

How Rhodium(I)-Catalyzed Phosphorus(III)-Directed C–H Bond Functionalizations Can Improve the Catalytic Activities of Phosphines

Trivalent-phosphorus-containing molecules are widely used in fields ranging from catalysis to materials science. Efficient catalytic methods for their modifications, providing straightforward access to novel hybrid structures with superior catalytic activities, are highly desired to facilitate reaction improvement or discovery. We have recently developed new methods for synthesizing polyfunctional phosphines by C–C cross-couplings through rhodium-catalyzed C–H bond activation. These methods use a native P(III) atom as a directing group, and can be used in regioselective late-stage functionalization of phosphine ligands. Interestingly, some of the modified phosphines outperform their parents in Pd-catalyzed cross-coupling reactions.1 Introduction2 Early Examples of Transition-Metal-Catalyzed P(III)-Directed C–H Bond Activation/Functionalizations3 Synthesis of Polyfunctional Biarylphosphines by Late-Stage Alkylation: Application in Carboxylation Reactions4 Synthesis of Polyfunctional Biarylphosphines by Late-Stage Alkenylation: Application in Amidation Reactions5 Conclusion

Discovery of solabiose phosphorylase and its application for enzymatic synthesis of solabiose from sucrose and lactose

Glycoside phosphorylases (GPs), which catalyze the reversible phosphorolysis of glycosides, are promising enzymes for the efficient production of glycosides. Various GPs with new catalytic activities are discovered from uncharacterized proteins phylogenetically distant from known enzymes in the past decade. In this study, we characterized Paenibacillus borealis PBOR_28850 protein, belonging to glycoside hydrolase family 94. Screening of acceptor substrates for reverse phosphorolysis, in which α-d-glucose 1-phosphate was used as the donor substrate, revealed that the recombinant PBOR_28850 produced in Escherichia coli specifically utilized d-galactose as an acceptor and produced solabiose (β-d-Glcp-(1 → 3)-d-Gal). This indicates that PBOR_28850 is a new GP, solabiose phosphorylase. PBOR_28850 catalyzed the phosphorolysis and synthesis of solabiose through a sequential bi-bi mechanism involving the formation of a ternary complex. The production of solabiose from lactose and sucrose has been established. Lactose was hydrolyzed to d-galactose and d-glucose by β-galactosidase. Phosphorolysis of sucrose and synthesis of solabiose were then coupled by adding sucrose, sucrose phosphorylase, and PBOR_28850 to the reaction mixture. Using 210 mmol lactose and 280 mmol sucrose, 207 mmol of solabiose was produced. Yeast treatment degraded the remaining monosaccharides and sucrose without reducing solabiose. Solabiose with a purity of 93.7% was obtained without any chromatographic procedures.

Preparation and the Catalytic Properties of Attapulgite / TiO2 Nanocomposites

With the rapid development of industry, the discharge of textile printing and dyeing wastewater will cause serious pollution to other pure water bodies. It is imperative to deal with textile printing and dyeing wastewater. In this paper, with titanium tetrachloride as a precursor, attapulgite (ATP) / TiO2 nanocomposites were prepared by a neutralizing hydrolysis method and their catalytic activities were investigated by the oxidative degradation of methylene blue dye using ozone as oxidant. The test results showed that there were significant interactions between TiO2 and ATP support. The effects were also studied of ozone concentration, catalyst amount, reaction temperature, and initial concentration of methylene blue on the degradation rate of methylene blue catalyzed by the prepared attapulgite / TiO2 nanocomposites, and under the optimal conditions, the methylene blue could be degraded more than 90% in 30 minutes. Compared with that of pure ATP, the catalytic activities of ATP / TiO2 nanocomposites were enhenced remarkably. The degradation mechanism of methylene blue was also discussed.

Crystal phase-selective synthesis of intermetallic palladium borides and phase-regulated (electro)catalytic properties

Three crystal phases of Pd-B intermetallics, including Pd6B, Pd5B2 and Pd2B, are synthesized, and their phase-dependent catalytic activities toward electrochemical water splitting and Suzuki coupling reaction are studied. In both...