One-pot Reduction Research Articles

Mild Metal-Free Hydrosilylation of Secondary Amides to Amines.

The combination of amide activation by Tf2O with B(C6F5)3-catalyzed hydrosilylation with TMDS constitutes a method for the one-pot reduction of secondary amides to amines under mild conditions. The method displays a broad applicability for the reduction of many types of substrates, and shows good compatibility and excellent chemoselectivity for many sensitive functional groups. Reductions of a multifunctionalized α,β-unsaturated amide obtained from another synthetic methodology, and a C-H functionalization product produced the corresponding amines in good to excellent yield. Chemoselective reduction of enantiomeric pure (ee >99%) tetrahydro-5-oxo-2-furaneamides yielded 5-(aminomethyl)dihydrofuran-2(3H)-ones in a racemization-free manner. The latter were converted in one pot to N-protected 5-hydroxypiperidin-2-ones, which are building blocks for the synthesis of many natural products. Further elaboration of an intermediate led to a concise four-step synthesis of (-)-epi-pseudoconhydrine.

One-pot Jeffery-Heck and Reduction Sequence: Synthesis of Alcohols and Applied to the Synthesis of Flavan Natural Products

An effective and practical sequential one-pot [Pd]-catalyzed Jeffery-Heck reaction followed by reduction protocol is designed for the direct synthesis of 1,3-diphenylpropan-1-ols and 3-phenylpropan-1-ols starting from allyl alcohols and iodoarenes. Interestingly, 1,3-diphenylpropan-1-ols are known to be the synthetic precursors of biologically active un-natural compounds. Moreover, the de-hydroxylated 1,3-diphenylpropan-1-ols, i. e., 1,3-diarylpropanes exist as core structure in griffithane natural products isolated from Combretum griffithii stems. In addition, these systems are potential synthetic precursors of flavans with diverse functionalities on aromatic rings. Significantly, the strategy was further extended to the synthesis of natural product 7-methoxy-3′,4′-methylenedioxy flavan, which has been isolated from plant of Ageratum conyzoides and the formal synthesis of the 4′-hydroxy-7-methoxy flavan, an anti-feedant compound isolated from Lycoris raliata species, from the corresponding 2’-bromo-1,3-diphenylpropan-1-ol precursors by using an effective copper-catalyzed intra-molecular Buchwald-Hartwig cross-coupling as a key transformation.

Solar-light photocatalytic disinfection using crystalline/amorphous low energy bandgap reduced TiO2.

A generation of reactive oxygen species (ROS) from TiO2 under solar light has been long sought since the ROS can disinfect organic pollutants. We found that newly developed crystalline/amorphous reduced TiO2 (rTiO2) that has low energy bandgap can effectively generate ROS under solar light and successfully remove a bloom of algae. The preparation of rTiO2 is a one-pot and mass productive solution-process reduction using lithium-ethylene diamine (Li-EDA) at room temperature. Interestingly only the rutile phase of TiO2 crystal was reduced, while the anatase phase even in case of both anatase/rutile phased TiO2 was not reduced. Only reduced TiO2 materials can generate ROS under solar light, which was confirmed by electron spin resonance. Among the three different types of Li-EDA treated TiO2 (anatase, rutile and both phased TiO2), the both phased rTiO2 showed the best performance to produce ROS. The generated ROS effectively removed the common green algae Chlamydomonas. This is the first report on algae degradation under solar light, proving the feasibility of commercially available products for disinfection.

ChemInform Abstract: Enantioselective Synthesis of α‐Hydroxy Amides and β‐Amino Alcohols from α‐Keto Amides.

Synthesis of enantiomerically enriched α-hydroxy amides and β-amino alcohols has been accomplished by enantioselective reduction of α-keto amides with hydrosilanes. A series of α-keto amides were reduced in the presence of chiral Cu(II)/(S)-DTBM-SEGPHOS catalyst to give the corresponding optically active α-hydroxy amides with excellent enantioselectivities by using (EtO)3SiH as a reducing agent. Furthermore, a one-pot complete reduction of both ketone and amide groups of α-keto amides has been achieved using the same chiral copper catalyst followed by tetra-n-butylammonium fluoride (TBAF) catalyst in presence of (EtO)3SiH to afford the corresponding chiral β-amino alcohol derivatives.

Site-Specific Conjugation of Peptides and Proteins via Rebridging of Disulfide Bonds Using the Thiol-Yne Coupling Reaction.

Herein, we describe an extension of our previously reported photomediated disulfide rebridging methodology to the conjugation of peptides and proteins. The methodology proved to be reproducible with various alkynes and different peptides. This study includes the first rebridging of the disulfide bond of a peptide through a thiol-yne reaction with a cyclooctyne. In all cases, the rebridging was proven by MS analyses and confirmed by the absence of olefinic protons on (1)H NMR spectra of the resulting products. Finally, this one-pot reduction thiol-yne conjugation was successfully applied to an antibody Fab fragment with a promising conversion, which set a good ground for the future syntheses of new protein and antibody conjugates.

One-step, stabilizer-free and green synthesis of Cu nanoclusters as fluorescent probes for sensitive and selective detection of nitrite ions

The instant and on-site detection of trace aqueous nitrite ions still remains a challenge for environmental monitoring and protection. In this work, we synthesized water-soluble striking fluorescent Cu nanoclusters (Cu NCs) by a green, simple, one-pot and stabilizer-free chemical reduction method. The fluorescence (FL) of the obtained Cu NCs can be selectively and efficiently quenched by the nitrite ions through the oxidation of Cu (0) atoms to Cu (I) in the core of Cu NCs. Under optimal conditions, two excellent linear relationships between the FL quenching degree of the Cu NCs and the concentrations of nitrite ions in the range of 0.0125–125μM and 125–5000μM with a low detection limit of 3.6nM were obtained. More importantly, the portable paper-based sensor has been explored for visual detection of trace nitrite ions in aqueous solution by the appearance of different degrees of blue FL under a UV lamp. The very simple and effective strategy reported here should facilitate the development of portable and reliable FL chemosensors for nitrite ions in pollution control.

One-Pot Fabrication of Mesoporous Core-Shell Au@PtNi Ternary Metallic Nanoparticles and Their Enhanced Efficiency for Oxygen Reduction Reaction.

Currently, Pt-based nanomaterials with tailorable shapes, structures, and morphologies are the most popular electrocatalysts for oxygen reduction reaction, which is a significant cathode reaction in fuel cells for renewable energy applications. We have successfully synthesized mesoporous core-shell Au@PtNi ternary metallic nanoparticles through a one-pot reduction method for cathodic materials used as oxygen reduction reaction catalysts. The as-synthesized nanoparticles exhibited superior catalytic activities and long-term stabilities compared with mesoporous core-shell Au@Pt nanoparticles and commercial Pt/C. The unique mesoporous core-shell structures as well as the alloy shells enable the enhanced electrochemical oxygen reduction reaction performances of the Pt-based materials via the electronic effect and geometric effect, holding great promise in fuel cell application.

ChemInform Abstract: Synthesis of New 2,4‐Disubstituted 2,3‐Dihydrobenzo[g]indol‐5‐ones by an SRN1 Strategy.

An original and short synthesis of substituted 2,3-dihydrobenzo[ g ]indol-5-ones by S RN 1-mediated synthesis of 2-nitroalkyl-substituted­ naphthalene-1,4-diones followed by a one-pot reduction–cyclization reaction is reported.

Nanoscale water soluble self-assembled zero-valent iron: role of stabilizers in their morphology

Self-assembled water soluble sheet-like zero-valent iron nano-composites were prepared using a simple one-pot chemical reduction method in an aqueous solution of FeCl3and NaBH4both with and without CTAB and SDS.

Active and regioselective rhodium catalyst supported on reduced graphene oxide for 1-hexene hydroformylation

An active and regioselective rhodium catalyst supported on reduced graphene oxide for 1-hexene hydroformylation was prepared by a one-pot liquid-phase reduction method.

ChemInform Abstract: Chiral Primary Amine Catalyzed Asymmetric Tandem Reduction—Michael Addition—Protonation Reaction Between Alkylidene Meldrum′s Acid and α‐Substituted Vinyl Ketones.

One-pot three-component tandem reduction–Michael addition–protonation reactions of alkylidene Meldrum’s acids to α-substituted vinyl ketones have been developed by using a chiral primary amine as the organocatalyst, affording the products in excellent yields and with good enantioselectivity.

Enantioselective Synthesis of α-Hydroxy Amides and β-Amino Alcohols from α-Keto Amides.

Synthesis of enantiomerically enriched α-hydroxy amides and β-amino alcohols has been accomplished by enantioselective reduction of α-keto amides with hydrosilanes. A series of α-keto amides were reduced in the presence of chiral Cu(II)/(S)-DTBM-SEGPHOS catalyst to give the corresponding optically active α-hydroxy amides with excellent enantioselectivities by using (EtO)3SiH as a reducing agent. Furthermore, a one-pot complete reduction of both ketone and amide groups of α-keto amides has been achieved using the same chiral copper catalyst followed by tetra-n-butylammonium fluoride (TBAF) catalyst in presence of (EtO)3SiH to afford the corresponding chiral β-amino alcohol derivatives.

One-Pot Reduction–Isomerization of α,β-Unsaturated Ketones

Key words ruthenium - enones - reduction - isomerization - mesoporous silica - heterogeneous catalysis

Creation of a new material stream from Japanese cedar resources to cellulose nanofibrils

Japanese cedar is one of the most abundant plantation softwoods in Japan, although it is not effectively utilized as a wood resource. Japanese cedar cellulose was isolated and subjected to one-pot catalytic oxidation and reduction with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and NaBH4, respectively. The TEMPO-oxidized and NaBH4-reduced Japanese cedar celluloses (TOCs-NaBH4) had carboxylate content of up to 1.4mmol/g and viscosity-average degrees of polymerization from 2000 to 3000. The X-ray diffraction patterns of the TOCs-NaBH4 showed that the crystal widths were ~3nm, indicating that the C6-OH groups present on the crystalline cellulose microfibril surfaces were selectively oxidized to C6-carboxylate groups. When the TOCs-NaBH4 with carboxylate content of 0.9–1.4mmol/g were mechanically disintegrated in water, transparent TEMPO-oxidized cellulose nanofibril (TOCN) dispersions were obtained. The lengths of the TOCNs, determined from their atomic force microscopy images, varied from 800 to 1500nm, depending on the oxidation conditions. The TOCNs prepared from Japanese cedar cellulose have an average of high aspect ratios (>300), which is greater than that (~150) prepared from wood pulp and thus advantageous.

ChemInform Abstract: An Oxazaborolidine‐Based Catalytic Method for the Asymmetric Synthesis of Chiral Allylic Alcohols.

Abstract The enantioselective reduction of a broad range of prochiral α,β-unsaturated ketones 1a – 1y using the oxazaborolidine-based catalyst providing chiral allylic alcohols 2a – 2y with both high enantioselectivity and chemoselectivity is described. The optimum reaction conditions were found using the oxazaborolidine catalysts prepared in situ from the chiral amino alcohols and borane reagents. Various chiral amino alcohols 4a – 4f were screened for this one-pot asymmetric reduction of α,β-enones. Amino alcohol 4a [( R )-DPP] and trimethylboroxine catalyze this asymmetric reduction in toluene at −20 °C within 0.5–2 h in a highly efficient manner. The synthesized chiral allylic alcohols 2a – 2y are new compounds, which are valuable intermediates in the preparation of new ligands and in the synthesis of several natural molecules.

Simultaneous electrochemical determination of epinephrine and uric acid in the presence of ascorbic acid using SnO2/graphene nanocomposite modified glassy carbon electrode

A novel biosensor has been constructed based on SnO2/graphene nanocomposite modified glassy carbon electrode (GCE) and was employed for the simultaneous determination of epinephrine (EP) and uric acid (UA) in the presence of common interferent ascorbic acid (AA) at physiological pH (7.0). SnO2/graphene composites were synthesized by a simple one-pot chemical reduction method. Physico-chemical analyses such as X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) revealed that the crystalline SnO2 nanoparticles were finely dispersed on the surface of graphene. The SnO2/graphene modified GCE exhibited enhanced electrocatalytic activity toward the oxidation of EP and UA when compared to the GO and SnO2 modified GCEs. Under the optimal conditions, the oxidation peak currents increased linearly with concentration over the wide range of 0.5–200μM and 0.1–200μM with the detection limits of 0.017μM and 0.28μM for EP and UA, respectively. The proposed modified electrode displayed high selectivity, good stability and reproducibility, and was successfully applied for the determination of epinephrine in epinephrine hydrochloride injection and uric acid in human urine samples.

Coordinated Fast Synthesis of Electrocatalytic Palladium Nanoparticles Decorated Graphene Oxide Nanocomposite for Fuel Cell. Applications.

Reduced graphene oxide and palladium nanoparticle (r-GO/Pd) nanocomposites were synthesized by an ecofriendly one-pot solid-state reduction method using ascorbic acid as a reducing agent. The coordinated formation of r-GO/Pd nanocomposite was observed within 2 min. The formed Pd nanoparticles (5 nm size) were uniformly distributed over the r-GO as characterized by X-ray powder diffraction, raman spectroscopy, scanning electron microscopy equipped with energy dispersive X-ray spectroscopy, and transmission electron microscopy. The cyclic voltammetric study revealed that the r-GO/Pd nanocomposite exhibited excellent electrocatalytic behavior toward the oxidation of alcohols in an alkaline medium. Our study proposes a cost-effective, easy, rapid, scalable, and environmentally friendly method for the synthesis of GO/metal nanoparticles hybrid catalytic material for electrochemical energy applications.

Gold-Coated Cobalt Ferrite Nanoparticles via Methionine-Induced Reduction

Functionalized superparamagnetic nanoparticles (Nps) are among the most investigated research topics. In this study, we present an efficient protocol for gold deposition onto the surface of cobalt ferrite (CoFe2O4) Nps by a simple one-pot reduction of AuCl4– ions with amino acid methionine, which, in turn, produces the biocompatible stabilizing shell. In contrast to previously reported gold deposition recipes, the one suggested herein is distinguished by the simplicity and prevention of monogold crystallite nucleation and growth in the deposition solution bulk. To demonstrate the preferential deposition of gold onto the surface of ferrite Nps, high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDX), inductively coupled plasma mass spectrometry, and Fourrier-transformed infrared spectroscopy (FTIR) investigations have been performed. The innovative gold deposition method is expected to open new horizons for the design of biocompatible water dispersible gold/meth...

Enhancement of ORR Activity of PtPd/C Alloy Catalyst with Accelerated Durability Test and Chemical De-Alloying

Introduction Usage amount of the expensive Pt cathode catalyst in the PEFCs should be reduced for their real commercialization. Core-shell structured catalyst, in which Pt monolayer (PtML) is formed on the other metal core surface, is one of the key technologies for the Pt usage reduction. Furthermore, it has been reported that ORR activity of the PtMLis enhanced when it is formed on Pd core nanoparticles [1, 2]. Recently, we successfully synthesized carbon supported Pd core-Pt shell structured catalyst (Pt/Pd/C) through a modified Cu under potential deposition (Cu-UPD) and Pt replacement processes, and we demonstrated that the ORR mass activity of the Pt/Pd/C catalyst is drastically enhanced with an accelerated durability test (ADT) performed at 80°C [3]. Although the modified Cu-UPD and Pt replacement are suitable processes for the mass-production of the catalyst, they are still complicated. In this study, carbon supported PtPd alloy catalyst (PtPd/C) was synthesized by a simple one-pot impregnation method. Changes in the ORR activity and microstructure of the catalyst with the ADT and chemical de-alloying (CDA) are investigated. Experimental The PtPd/C alloy catalyst was synthesized with a one-pot impregnation reduction process. Pt(C2O4) and Pd(NO3)2 were dissolved in water and a carbon support (Vulcan XC-72R) was ultrasonically dispersed, followed by evaporation of H2O. The resultant mixture was heat-treated at 600oC for 4 h in 15% H2/85% Ar atmosphere. The PtPd/C catalyst was characterized with TG, XRF, XRD, TEM, TEM-EDX, CV and CO stripping voltammetry. The ORR activity of the catalyst was evaluated by RDE technique in O2 saturated 0.1 M HClO4 at 25°C. The ADT was performed using a rectangular wave potential cycling (0.6 V (3 s)-1.0 V (3 s) vs. RHE) in Ar saturated 0.1 M HClO4 at 80°C for 10,000 cycles. CDA treatment was carried out in 2 M H2SO4 containing 10 mM CuSO4with coexistence of metallic Cu sheet. The PtPd/C catalyst was dispersed in the solution and stirred at 60°C for 24 h with air bubbling. Results and Discussion XRF analysis revealed that composition of as-synthesized PtPd/C catalyst is Pt20Pd80 (atomic %) and XRD pattern showed that Pt and Pd are well alloyed in the catalyst. CVs of the Pt20Pd80/C catalyst are shown in Fig. 1. Hydrogen absorption peak can be clearly observed in the as-synthesized PtPd/C catalyst in 0.05-0.1 V, implying that Pd exists on the surface of the as-synthesized PtPd nanoparticle catalyst. On the contrary, the hydrogen absorption peak almost disappeared with the ADT and the CDA, suggesting that the surface Pd atoms dissolved and Pt shell was formed. We conducted TEM-EDX elemental mapping and line analysis of the PtPd/C catalysts (Fig. 2), which showed that the catalyst changed into quasi core-shell structured catalyst with the ADT and the CDA. Figure 3 summarizes the ORR mass activity of the PtPd/C catalyst in comparison with that of a carbon supported Pt reference catalyst (Pt/C, Pt size: 2.8 nm, Pt loading: 46 wt.%, TEC10E50E, TKK). The ORR mass activity of the PtPd/C catalyst was enhanced by 1.5-2.1 times of the Pt/C catalyst with the ADT and the CDA, and the CDA treated PtPd/C catalyst retained 81% of the ORR mass activity even after the ADT. It was demonstrated that the PtPd/C alloy catalyst synthesized with the simple one-pot impregnation method is an alternative to the Pt/C catalyst for the PEFC. Acknowledgement This work was supported by New Energy and Industrial Technology Development Organization (NEDO), Japan.

Synergetic effect of metal nickel and graphene as a cocatalyst for enhanced photocatalytic hydrogen evolution via dye sensitization.

Exploiting new, low-cost and efficient electrocatalysts for hydrogen evolution reaction (HER) is important to resolve the energy crisis and environment pollution. In this work, graphene decorated with Ni nanoparticles (NPs) were synthesized via one-pot reduction using graphene oxide (GO, the obtained composite was denoted as GN) as a precursor. The as-prepared composite GN exhibits much better electrocatalytic and dye-sensitized HER activities than single Ni and reduced graphene oxide (RGO), namely, a great synergetic effect of RGO and Ni for HER. The coupling of metal Ni with the defect carbons of RGO plays a key role in the synergetic effect. The structure of GN composites is another key factor to the synergetic effect. The highest apparent quantum yield (AQY) for dye-sensitized photocatalytic hydrogen evolution at 470 nm reaches 30.3% under the optimal conditions.