Identification of Alkoxy Radicals as Hydrogen Atom Transfer Agents in Ce-Catalyzed C-H Functionalization.

The intermediacy of alkoxy radicals in cerium-catalyzed C-H functionalization via H-atom abstraction has been unambiguously confirmed. Catalytically relevant Ce(IV)-alkoxide complexes have been synthesized and characterized by X-ray diffraction. Operando electron paramagnetic resonance and transient absorption spectroscopy experiments on isolated pentachloro Ce(IV) alkoxides identified alkoxy radicals as the sole heteroatom-centered radical species generated via ligand-to-metal charge transfer (LMCT) excitation. Alkoxy-radical-mediated hydrogen atom transfer (HAT) has been verified via kinetic analysis, density functional theory (DFT) calculations, and reactions under strictly chloride-free conditions. These experimental findings unambiguously establish the critical role of alkoxy radicals in Ce-LMCT catalysis and definitively preclude the involvement of chlorine radical. This study has also reinforced the necessity of a high relative ratio of alcohol vs Ce for the selective alkoxy-radical-mediated HAT, as seemingly trivial changes in the relative ratio of alcohol vs Ce can lead to drastically different mechanistic pathways. Importantly, the previously proposed chlorine radical-alcohol complex, postulated to explain alkoxy-radical-enabled selectivities in this system, has been examined under scrutiny and ruled out by regioselectivity studies, transient absorption experiments, and high-level calculations. Moreover, the peculiar selectivity of alkoxy radical generation in the LMCT homolysis of Ce(IV) heteroleptic complexes has been analyzed and back-electron transfer (BET) may have regulated the efficiency and selectivity for the formation of ligand-centered radicals.

Photocatalytic Dehydroxymethylative Arylation by Synergistic Cerium and Nickel Catalysis.

Under mild reaction conditions with inexpensive cerium and nickel catalysts, easily accessible free alcohols can now be utilized as operationally simple and robust carbon pronucleophiles in selective C(sp3)-C(sp2) cross-couplings. Facilitated by automated high-throughput experimentation, sterically encumbered benzoate ligands have been identified for robust cerium complexes, enabling the synergistic cooperation of cerium catalysis in the emerging metallaphotoredox catalysis. A broad range of free alcohols and aromatic halides can be facilely employed in this transformation, representing a new paradigm for the C(sp3)-C(sp2) bond construction between free alcohols and aryl halides with the extrusion of formaldehyde. Moreover, mechanistic investigations have been conducted, leading to the identification of a tribenzoate cerium(III) complex as a viable intermediate.

Cerium-Catalyzed C-H Functionalizations of Alkanes Utilizing Alcohols as Hydrogen Atom Transfer Agents.

Modern photoredox catalysis has traditionally relied upon metal-to-ligand charge-transfer (MLCT) excitation of metal polypyridyl complexes for the utilization of light energy for the activation of organic substrates. Here, we demonstrate the catalytic application of ligand-to-metal charge-transfer (LMCT) excitation of cerium alkoxide complexes for the facile activation of alkanes utilizing abundant and inexpensive cerium trichloride as the catalyst. As demonstrated by cerium-catalyzed C-H amination and the alkylation of hydrocarbons, this reaction manifold has enabled the facile use of abundant alcohols as practical and selective hydrogen atom transfer (HAT) agents via the direct access of energetically challenging alkoxy radicals. Furthermore, the LMCT excitation event has been investigated through a series of spectroscopic experiments, revealing a rapid bond homolysis process and an effective production of alkoxy radicals, collectively ruling out the LMCT/homolysis event as the rate-determining step of this C-H functionalization.

Enantioselective Ni-Catalyzed Electrochemical Synthesis of Biaryl Atropisomers.

A scalable enantioselective nickel-catalyzed electrochemical reductive homocoupling of aryl bromides has been developed, affording enantioenriched axially chiral biaryls in good yield under mild conditions using electricity as a reductant in an undivided cell. Common metal reductants such as Mn or Zn powder resulted in significantly lower yields in the absence of electric current under otherwise identical conditions, underscoring the enhanced reactivity provided by the combination of transition metal catalysis and electrochemistry.

Nickel-catalyzed Enantioselective Hydroarylation and Hydroalkenylation of Styrenes.

We have developed a Ni-catalyzed enantioselective hydroarylation of styrenes with arylboronic acids using MeOH as the hydrogen source, providing an efficient method to access 1,1-diarylalkanes, which are essential structural units in many biologically active compounds. In addition, Ni-catalyzed enantioselective hydrovinylation of styrenes with vinylboronic acids is also realized with good yields and enantioselectivities. The synthetic utility was demonstrated by the efficient synthesis of ( R)-(-)-ibuprofen.

Broadband focusing and demultiplexing of surface plasmon polaritons on metal surface by holographic groove patterns.

Manipulation of surface plasmon polaritons (SPPs) on metal surfaces is important for constructing ultracompact integrated micro/nano optical devices and systems. We employ the method of surface electromagnetic wave holography (SWH) to design holographic groove patterns for managing the transport of broadband SPPs on metal surface. Several sets of groove patterns corresponding to different wavelengths are etched on the same region on metal surface to form a broadband SPP hologram. The incident SPPs are scattered by the composite hologram and interfere with each other to focus at different or the same positions for SPPs of different wavelengths. Finite-difference time-domain simulations show that broadband demultiplexing of SPPs is realized by the designed plasmonic holographic structures. In addition, the broadband SPPs can be focused to a pre-designated spot by a designed plasmonic hologram and as a result focusing of an ultrashort plasmonic pulse can be achieved. The results show that the SWH can successfully handle design of plasmonic holographic structures for SPPs wavelength management on metal surface.

Direct method to control surface plasmon polaritons on metal surfaces.

The manipulation of surface plasmon polaritons (SPPs) on metal surfaces is an important aspect in the design of ultra-compact integrated micro/nano optical systems. We present a direct method for the easy, yet accurate design of complicated groove patterns to control SPPs traveling on metal surfaces, using a surface electromagnetic wave holography method, based on the Huygens-Fresnel principle. SPPs are scattered by these deliberately and appropriately determined groove patterns and interfere with each other to form new paths with desire. Two devices are demonstrated, with predesignated functionalities fully implemented by the designed plasmonic holographic structures, according to the finite-difference time-domain simulations. The results strongly indicate that this direct method is effective, efficient, and user friendly in its application to control SPPs on metal surfaces.

Early enteral fat supplement and fish oil increases fat absorption in the premature infant with an enterostomy.

OBJECTIVE: To test the hypothesis that in the premature infant with an enterostomy, early enteral supplementation with Microlipid (fat supplement) and fish oil increases enteral fat absorption and decreases the requirement for Intralipid (intravenous fat emulsion). STUDY DESIGN: Premature infants (<2 months old) with an enterostomy after surgical treatment for necrotizing enterocolitis or spontaneous intestinal perforation and tolerating enteral feeding at 20 mL/kg/day were randomized to usual care (control 18 infants) or early supplementing enteral fat and fish oil (treatment 18 infants). Intravenous fat emulsion was decreased as enteral fat intake was increased. Daily weight, ostomy output, and nutrition data were recorded. Weekly 24-hour ostomy effluent was collected until bowel reanastomosis, and fecal fat, fecal liquid, and dry feces were measured. Fat absorption (g/kg/d) was calculated by subtracting fecal fat from dietary fat. The fecal liquid and dry feces were reported as mg/g wet stool. Date were analyzed by using ANOVA and mixed-effects model. RESULTS: The interval from initial postoperative feeding to bowel reanastomosis varied from 2 to 10 weeks. The treatment group received more dietary fat and less intravenous fat emulsion and had higher enteral fat absorption, less fecal liquid, and drier feces than the control group. These effects were greater among infants with a high ostomy compared with those with a low ostomy. Enteral fat intake was significantly correlated with fat absorption. CONCLUSION: Early enteral fat supplement and fish oil increases fat absorption and decreases the requirement for intravenous fat emulsion. This approach could be used to promote bowel adaptation and reduce the use of intravenous fat emulsion in the premature infant with an enterostomy.

High-performance reduced graphene oxide supercapacitors enabled by simple amino hydroquinone dimethylether.

Reduced graphene oxide (rGO) supercapacitors usually feature poor capacitive characteristics. In the current work, coupling of the simple, nonclassical redox molecule amino hydroquinone dimethylether with rGO was found to boost the rGO capacitance to 523 F g-1. The assembled device exhibited an energy density of 143 Wh kg-1 and excellent rate capability and cyclability.

Dietary fish oil increases fat absorption and fecal bile acid content without altering bile acid synthesis in 20-d-old weanling rats following massive ileocecal resection.

INTRODUCTION: Dietary fish oil (FO) was reported to lower fecal fat excretion in a weanling rat model of short bowel syndrome (SBS) after ileocecal resection (ICR), and to induce changes in secretion and synthesis of bile acid (BA) in adults. We hypothesized that dietary FO, as compared with corn oil (CO), increases intestinal fat absorption in weanling SBS rats in part due to increased hepatic BA synthesis and luminal BA concentrations. METHODS: After undergoing ICR, 20-d-old rats were fed ad lib for 7 d with a CO or FO diet containing 5% sucrose polybehenate (SPB), a marker for dietary fat absorption. Fecal fatty acid, fecal and intestine luminal BA, liver mRNA expressions of cholesterol 7α-hydroxylase (Cyp7α1) and sterol-12α-hydroxylase (Cyp8ß1), and serum 7α-hydroxy-4-cholesten-3-1 (7αC4) levels were determined. RESULTS: As compared with CO-ICR rats, FO-ICR rats had higher intestinal absorption of total fat and most individual fatty acids. Although the BA content per gram of dry stool was increased in FO-ICR rats, there were no differences between groups for the BA content in remnant jejunum, liver mRNA expression of BA biosynthetic enzymes, Cyp7α1 and Cyp8ß1, or serum 7αC4, a marker for BA synthesis. CONCLUSION: Dietary FO increases dietary fat absorption without increasing hepatic BA synthesis in weanling SBS rats.

Water as a Hydrogenating Agent: Stereodivergent Pd-Catalyzed Semihydrogenation of Alkynes.

Palladium-catalyzed transfer semihydrogenation of alkynes using H2O as the hydrogen source and Mn as the reducing reagent is developed, affording cis- and trans-alkenes selectively under mild conditions. In addition, this method provides an efficient way to access various cis-1,2-dideuterioalkenes and trans-1,2-dideuterioalkenes by using D2O instead of H2O.

Regioselective Ni-Catalyzed Carboxylation of Allylic and Propargylic Alcohols with Carbon Dioxide.

An efficient Ni-catalyzed reductive carboxylation of allylic alcohols with CO2 has been successfully developed, providing linear ß,γ-unsaturated carboxylic acids as the sole regioisomer with generally high E/Z stereoselectivity. In addition, the carboxylic acids can be generated from propargylic alcohols via hydrogenation to give allylic alcohol intermediates, followed by carboxylation. A preliminary mechanistic investigation suggests that the hydrogenation step is made possible by a Ni hydride intermediate produced by a hydrogen atom transfer from water.

Realization of Plasmonic Microcavity with Full Transverse and Longitudinal Mode Selection.

Surface plasmon polaritons (SPPs) manipulation is of vital importance to construct ultracompact integrated micro/nano-optical devices and systems. Here we report the design, fabrication, and characterization of a SPP microcavity with full transverse and longitudinal mode selection and control on the surface of gold film. The designed microcavity supports the fundamental and first-order transverse modes of Gaussian mode beam with controllable longitudinal modes, respectively. The transverse mode is determined by two holographic mirrors made from deliberately designed groove patterns via the surface electromagnetic wave holography methodology, while the longitudinal mode is determined by the length of cavity. Both numerical simulations and leaky-wave SPP mode observations confirm the realization of full mode selection in the fabricated cavity. Our work opens up a powerful way to fully explore longitudinal and transverse mode control in SPP microcavities, which will be beneficial for light-matter interaction enhancement, construction of novel SPP nanolaser and microlaser, optical sensing, and optical information processing.

Early enteral fat supplementation improves protein absorption in premature infants with an enterostomy.

BACKGROUND: Early enteral fat supplementation and fish oil (FO) stimulates post-resection intestinal adaptation in rats and increases fat absorption in premature infants with bowel resection and an enterostomy. OBJECTIVE: To test the hypothesis that early fat supplement and FO increases post-resection protein absorption, intestinal RNA, protein without decreasing intestinal arachidonic acid (AA) in premature infants with an enterostomy. METHODS: 36 premature infants (<2 months old) with an enterostomy after surgical treatment for necrotizing enterocolitis or spontaneous intestinal perforation who tolerated enteral feeding at 20 ml/kg/day were randomized to usual care (control, n = 18) or early supplementing enteral Microlipid (ML) and FO (treatment, n = 18). Intralipid was decreased as the dose of enteral fat was increased. Daily weight, ostomy output and nutritional intake were recorded. Weekly 24-hour ostomy effluent was collected to measure fecal protein. Protein absorption was calculated by subtracting fecal protein from dietary protein. Tissue samples from the functional stoma and the nonfunctional distal diverted end were collected during bowel reanastomosis to measure RNA, protein, and fatty acid (FA) profile. RESULTS: Compared to controls, the treatment group had higher protein absorption (g/kg/day) and intestinal RNA and protein (µg/mg tissue) proximal to the ostomy. The two groups had similar FA profiles except that the treatment group had higher n-3 eicosapentaenoic acid (EPA, µg/mg tissue) proximal to the ostomy. CONCLUSION: Early supplementation of enteral ML and FO to premature infants with an enterostomy increased dietary protein absorption, intestinal RNA, protein and n-3 EPA content without altering other FA content.