High Nitrile Yields of Aerobic Ammoxidation of Alcohols Achieved by Generating •O2- and Br• Radicals over Iron-Modified TiO2 Photocatalysts.

Catalytic ammoxidation of alcohols into nitriles is an essential reaction in organic synthesis. While highly desirable, conducting the synthesis at room temperature is challenging, using NH3 as the nitrogen source, O2 as the oxidant, and a catalyst without noble metals. Herein, we report robust photocatalysts consisting of Fe(III)-modified titanium dioxide (Fe/TiO2) for ammoxidation reactions at room temperature utilizing oxygen at atmospheric pressure, NH3 as the nitrogen source, and NH4Br as an additive. To the best of our knowledge, this is the first example of catalytic ammoxidation of alcohols over a photocatalyst using such cheap and benign materials. Various (hetero) aromatic nitriles were synthesized at high yields, and aliphatic alcohols could also be transformed into corresponding nitriles at considerable yields. The modification of TiO2 with Fe(III) facilitates the formation of active •O2- radicals and increases the adsorption of NH3 and amino intermediates on the catalyst, accelerating the ammoxidation to yield nitriles. The additive NH4Br impressively improves the catalytic efficiency via the formation of bromine radicals (Br•) from Br-, which works synergistically with •O2- to capture H• from Cα-H, which is present in benzyl alcohol and the intermediate aldimine (RCH═NH), to generate the active carbon-centered radicals. Further, the generation of Br• from the Br- additive consumes the photogenerated holes and OH• radicals to prevent over-oxidation, significantly improving the selectivity toward nitriles. This amalgamation of function and synergy of the Fe(III)-doped TiO2 and NH4Br reveals new opportunities for developing semiconductor-based photocatalytic systems for fine chemical synthesis.

Noninvasive prenatal diagnosis targeting fetal nucleated red blood cells.

Noninvasive prenatal diagnosis (NIPD) aims to detect fetal-related genetic disorders before birth by detecting markers in the peripheral blood of pregnant women, holding the potential in reducing the risk of fetal birth defects. Fetal-nucleated red blood cells (fNRBCs) can be used as biomarkers for NIPD, given their remarkable nature of carrying the entire genetic information of the fetus. Here, we review recent advances in NIPD technologies based on the isolation and analysis of fNRBCs. Conventional cell separation methods rely primarily on physical properties and surface antigens of fNRBCs, such as density gradient centrifugation, fluorescence-activated cell sorting, and magnetic-activated cell sorting. Due to the limitations of sensitivity and purity in Conventional methods, separation techniques based on micro-/nanomaterials have been developed as novel methods for isolating and enriching fNRBCs. We also discuss emerging methods based on microfluidic chips and nanostructured substrates for static and dynamic isolation of fNRBCs. Additionally, we introduce the identification techniques of fNRBCs and address the potential clinical diagnostic values of fNRBCs. Finally, we highlight the challenges and the future directions of fNRBCs as treatment guidelines in NIPD.

Biomass-Derived Single Zn Atom Catalysts: The Multiple Roles of Single Zn Atoms in the Oxidative Cleavage of C-N Bonds.

The C-N bond cleavage represents one kind of important organic and biochemical transformation, which has attracted great interest in recent years. The oxidative cleavage of C-N bonds in N,N-dialkylamines into N-alkylamines has been well documented, but it is challenging in the further oxidative cleavage of C-N bonds in N-alkylamines into primary amines due to the thermally unfavorable release of α-position H from N-Cα-H and the paralleling side reactions. Herein, a biomass-derived single Zn atom catalyst (ZnN4-SAC) was discovered to be a robust heterogeneous non-noble catalyst for the oxidative cleavage of C-N bonds in N-alkylamines with O2 molecules. Experimental results and DFT calculation revealed that ZnN4-SAC not only activates O2 to generate superoxide radicals (·O2 -) for the oxidation of N-alkylamines to generate imine intermediates (C=N), but the single Zn atoms also served as the Lewis acid sites to promote the cleavage of C=N bonds in imine intermediates, including the first addition of H2O to generate α-hydroxylamine intermediates and the following C-N bond cleavage via a H atom transfer process.

Nitrogen-Doped Carbon as a Highly Active Metal-Free Catalyst for the Selective Oxidative Dehydrogenation of N-Heterocycles.

N-heteroarenes represents one of the most important chemicals in pharmaceuticals and other bio-active molecules, which can be easily accessed from the oxidation of N-heterocycles over metal catalysts. Herein, the metal-free oxidative dehydrogenation of N-heterocycles into N-heteroarenes was developed using molecular oxygen as the terminal oxidant. The nitrogen-doped carbon materials were facilely prepared via the simple pyrolysis process using biomass (carboxymethyl cellulose sodium) and dicyandiamide as the carbon and nitrogen source, respectively, and they were discovered to be robust for the oxidative dehydrogenation of N-heterocycles into N-heteroarenes under mild conditions (80 °C under 1 bar O2 ) with water as the green solvent. Diverse N-heterocycles including 1,2,3,4-tetrahydroisoquinolines, indolines and 1,2,3,4-tetrahydroquinoxalines were smoothly converted into N-heteroarenes with high to excellent yields (76->99 %). Superoxide radical (⋅O2 - ) and hydroxyl radical (⋅OH) were probed as the reactive oxygen species for the oxidation of N-heterocycles into N-heteroarenes. More importantly, the nitrogen-doped carbon catalyst can be reused with a high stability. The method provides an environmentally friendly and economical route to access important N-hetero-aromatic commodities.

Amberlyst-15 supported zirconium sulfonate as an efficient catalyst for Meerwein-Ponndorf-Verley reductions.

The Meerwein-Ponndorf-Verley (MPV) reaction is an important chemoselective route for carbonyl group hydrogenation, and thus designing new and effective catalysts for this transformation remains important and challenging. In this work, a new sulfonate coordinated Zr(IV) catalyst was prepared by the coordination of Zr(IV) onto the sulfonate groups of Amberlyst-15, which can effectively catalyze the MPV reaction and quantitatively convert carbonyl compounds to the corresponding alcohols with high reactivity and stability. Detailed mechanistic investigations reveal that the catalytic performance of Zr-AIER can be attributed to the synergetic effect between Zr4+ and the sulfonate group, and the porous structure with high surface area.

An enzyme-mimic single Fe-N3 atom catalyst for the oxidative synthesis of nitriles via C─C bond cleavage strategy.

The cleavage and functionalization of recalcitrant carbon─carbon bonds is highly challenging but represents a very powerful tool for value-added transformation of feedstock chemicals. Here, an enzyme-mimic iron single-atom catalyst (SAC) bearing iron (III) nitride (FeN3) motifs was prepared and found to be robust for cleavage and cyanation of carbon-carbon bonds in secondary alcohols and ketones. High nitrile yields are obtained with a wide variety of functional groups. The prepared FeN3-SAC exhibits high enzyme-like activity and is capable of generating a dioxygen-to-superoxide radical at room temperature, while the commonly reported FeN4-SAC bearing FeN4 motifs was inactive. Density functional theory (DFT) calculation reveals that the activation energy of dioxygen activation and the activation energy of the rate-determining step of nitrile formation are lower over FeN3-SAC than FeN4-SAC. In addition, DFT calculation also explains the catalyst's high selectivity for nitriles.