A first-principles investigation of α, β, and γ-MnO2 as potential cathode materials in Al-ion batteries

An inexpensive and eco-friendly alternative energy storage solution is becoming more in demand as the world moves towards greener technology. We used first principles calculations to investigate α, β, and γ-MnO₂ and their Al-ion intercalation mechanism in potential applications for aluminum batteries. We explored these complexes through investigating properties such as volume change, binding/diffusion energy, and band gap to gauge each material. α-MnO₂ had almost no volume change. γ-MnO₂ had the lowest binding energy and diffusion barrier. Our study gives insight into the feasibility of using MnO₂ in aluminum batteries and guides investigation of the material within its different phases.

An inexpensive and eco-friendly alternative energy storage solution is becoming more in demand as the world moves towards greener technology.     

Ultrathin δ-MnO2 nanoflakes with Na+ intercalation as a high-capacity cathode for aqueous zinc-ion batteries

Pristine δ-MnO₂ as the typical cathode for rechargeable zinc-ion batteries (ZIBs) suffers from sluggish reaction kinetics, which is the key issue to prepare high-performance manganese-based materials. In this work, Na⁺ incorporated into layered δ-MnO₂ (NMO) was prepared for ZIB cathodes with high capacity, high energy density, and excellent durable stability. By an effective fabricated strategy of hydrothermal synthesis, a three-dimensional interconnected δ-MnO₂ nanoflake network with Na⁺ intercalation showed a uniform array arrangement and high conductivity. Also, the H⁺ insertion contribution in the NMO cathode to the discharge capacity confirmed the fast electrochemical charge transfer kinetics due to the enhanced ion conductivity from the insertion of Na⁺ into the interlayers of the host material. Consequently, a neutral aqueous NMO-based ZIB revealed a superior reversible capacity of 335 mA h g⁻¹, and an impressive durability over 1000 cycles, and a peak gravimetric energy output of 459 W h kg⁻¹. As a proof of concept, the as-fabricated quasi-solid-state ZIB exhibited a remarkable capacity of 284 mA h g⁻¹ at a current density of 0.5 A g⁻¹, and good practicability. This research demonstrated a significant enhancement of the electrochemical performance of MnO₂-based ZIBs by the intercalation of Na⁺ to regulate the microstructure and boost the electrochemical kinetics of the δ-MnO₂ cathode, thus providing a new insight for high-performance aqueous ZIBs.

Sodium-ion intercalated δ-MnO₂ nanoflakes are applied in an aqueous rechargeable zinc battery cathode with high energy density and excellent durable stability.     

Simultaneous determination of methadone and morphine at a modified electrode with 3D β-MnO2 nanoflowers: application for pharmaceutical sample analysis

The present research synthesized manganese dioxide nano-flowers (β-MnO₂-NF) via a simplified technique for electro-catalytic utilization. Moreover, morphological characteristics and X-ray analyses showed Mn in the oxide form with β-type crystallographic structure. In addition, the research proposed a new efficient electro-chemical sensor to detect methadone at the modified glassy carbon electrode (β-MnO₂-NF/GCE). It has been found that oxidizing methadone is irreversible and shows a diffusion controlled procedure at the β-MnO₂-NF/GCE. Moreover, β-MnO₂-NF/GCE was considerably enhanced in the anodic peak current of methadone related to the separation of morphine and methadone overlapping voltammetric responses with probable difference of 510 mV. In addition, a linear increase has been observed between the catalytic peak currents gained by the differential pulse voltammetry (DPV) of morphine and methadone and their concentrations in the range between 0.1–200.0 μM and 0.1–250.0 μM, respectively. Furthermore, the limits of detection (LOD) for methadone and morphine were found to be 5.6 nM and 8.3 nM, respectively. It has been found that our electrode could have a successful application for detecting methadone and morphine in the drug dose form, urine, and saliva samples. Thus, this condition demonstrated that β-MnO₂-NF/GCE displays good analytical performances for the detection of methadone.

Electrochemical sensor based on β-MnO₂ nanoflower-modified glassy carbon electrode for the simultaneous detection of methadone and morphine was fabricated.     

Direct β-selectivity of α,β-unsaturated γ-butyrolactam for asymmetric conjugate additions in an organocatalytic manner

The β-selective asymmetric addition of γ-butyrolactam with cyclic imino esters catalyzed by a bifunctional chiral tertiary amine has been developed, which provides an efficient access to optically active β-position functionalized pyrrolidin-2-one derivatives in both high yield and enantioselectivity (up to 78% yield and 95 : 5 er). This is the first catalytic method to access chiral β-functionalized pyrrolidin-2-one via a direct organocatalytic approach.

The asymmetric addition of γ-butyrolactam with cyclic imino esters catalyzed by (DHQD)₂AQN has been developed, which provides an access to β-position functionalized pyrrolidin-2-one derivatives in high levels yield and enantioselectivity.

Metal-free organocatalytic asymmetric transformations have successfully captured considerable enthusiasm of chemists as powerful methods for the synthesis of various kinds of useful chiral compounds ranging from the preparation of biologically important molecules through to novel materials.¹ Chiral pyrrolidin-2-ones have been recognized as important structural motifs that are frequently encountered in a variety of biologically active natural and synthetic compounds.² In particular, the β-position functionalized pyrrolidin-2-one backbones, which can serve as key synthetic precursors for inhibitory neurotransmitters γ-aminobutyric acids (GABA),³ selective GABA_B receptor agonists⁴ as well as antidepressant rolipram analogues,⁵ have attracted a great deal of attention. Therefore, the development of highly efficient, environmentally friendly and convenient asymmetric synthetic methods to access these versatile frameworks is particularly appealing.As a direct precursor to pyrrolidin-2-one derivatives, recently, α,β-unsaturated γ-butyrolactam has emerged as the most attractive reactant in asymmetric organometallic or organocatalytic reactions for the synthesis of chiral γ-position functionalized pyrrolidin-2-ones (Scheme 1). These elegant developments have been achieved in the research area of catalytic asymmetric vinylogous aldol,⁶ Mannich,⁷ Michael⁸ and annulation reactions⁹ in the presence of either metal catalysts or organocatalysts (a, Scheme 1). These well-developed catalytic asymmetric methods have been related to the γ-functionalized α,β-unsaturated γ-butyrolactam to date. However, in sharp contrast, the approaches toward introducing C-3 chirality at the β-position of butyrolactam through a direct catalytic manner are underdeveloped (b, Scheme 1)¹⁰ in spite of the fact that β-selective chiral functionalization of butyrolactam can directly build up α,β-functionalized pyrrolidin-2-one frameworks.Open in a separate windowScheme 1Different reactive position of α,β-unsaturated γ-butyrolactam in catalytic asymmetric reactions.So far, only a few metal-catalytic enantioselective β-selective functionalized reactions have been reported. For examples, a rhodium/diene complex catalyzed efficient asymmetric β-selective arylation^10a and alkenylation^10b have been reported by Lin group (a, Scheme 2). Procter and co-workers reported an efficient Cu(i)–NHC-catalyzed asymmetric silylation of unsaturated lactams (b, Scheme 2).^10c Despite these creative works, considerable challenges still exist in the catalytic asymmetric β-selective functionalization of γ-butyrolactam. First, the scope of nucleophiles is limited to arylboronic acids, potassium alkenyltrifluoroborates and PhMe₂SiBpin reagents. Second, the catalytic system and activation mode is restricted to metal/chiral ligands. To our knowledge, an efficient catalytic method to access chiral β-functionalized pyrrolidin-2-one via a direct organocatalytic approach has not yet been established. Therefore, the development of organocatalytic asymmetric β-selective functionalization of γ-butyrolactam are highly desirable. In conjunction with our continuing efforts in building upon chiral precedents by using chiral tertiary amine catalytic system,¹¹ we rationalized that the activated α,β-unsaturated γ-butyrolactam might serve as a β-position electron-deficient electrophile. This γ-butyrolactam may react with a properly designed electron-rich nucleophile to conduct an expected β-selective functionalized reaction of γ-butyrolactam under a bifunctional organocatalytic fashion, while avoiding the direct γ-selective vinylogous addition reaction or β,γ-selective annulation as outlined in Scheme 2. Herein we report the β-selective asymmetric addition of γ-butyrolactam with cyclic imino esters¹² catalyzed by a bifunctional chiral tertiary amine, which provides an efficient and facile access to optically active β-position functionalized pyrrolidin-2-one derivatives with both high diastereoselectivity and enantioselectivity.Open in a separate windowScheme 2β-Selective functionalization of γ-butyrolactam via metal- (previous work) or organo- (this work) catalytic approach.To begin our initial investigation, several bifunctional organocatalysts¹³ were firstly screened to evaluate their ability to promote the β-selective asymmetric addition of γ-butyrolactam 2a with cyclic imino ester 3a in the presence of 15 mol% of catalyst loading at room temperature in CH₂Cl₂ (entries 1–6,

The formation and metabolism of 3α,7α-dihydroxy-5β-cholestan-26-oic acid in man

The formation and metabolism of a naturally occurring C(27) bile acid, 3alpha,7alpha-dihydroxy-5beta-cholestan-26-oic acid, was studied in patients with T-tube bile fistulas. C-26-cholesterol-(14)C was shown to be converted to this C(27) bile acid. After synthesis and labeling with tritium, 3alpha,7alpha-dihydroxy-5beta-cholestan-26-oic acid was efficiently metabolized to chenodeoxycholic acid. After oral and i.v. administration there was conversion of about 80% of the administered amount to chenodeoxycholic acid. A small amount, less than 2% of the administered radioactivity, was converted to cholic acid. The remainder of the radioactivity was excreted in two unidentified peaks of radioactivity.The results of this study demonstrate that 3alpha,7alpha-dihydroxy-5beta-cholestan-26-oic acid is a metabolic product of cholesterol and is further metabolized, predominantly to chenodeoxycholic acid and to a minor extent to cholic acid in man.     

Oxygen Equilibrium Characteristics of Abnormal Hemoglobins: Hirose (α2β237Ser), L Ferrara (α247Glyβ2), Broussais (α290Asnβ2), and Dhofar (α2β258Arg)

The oxygen equilibrium characteristics of four structural variants of hemoglobin A were correlated with their amino acid substitutions.Hemoglobin Dhofar, in which the proline at E2(58)beta is replaced by arginine, had normal oxygen equilibrium characteristics.Hemoglobin L Ferrara. in which the aspartic acid at CD5(47)alpha is replaced by glycine, and hemoglobin Broussais, in which the lysine at FG2(90)alpha is replaced by asparagine, both showed a slightly elevated oxygen affinity; nevertheless both demonstrated a normal heme-heme interaction and a normal Bohr effect.Hemoglobin Hirose, in which the tryptophan at C3 (37)beta is replaced by serine, showed abnormalities of all oxygen equilibrium characteristics; i.e., increased oxygen affinity, diminished heme-heme interaction, and reduced Bohr effect.These results suggest that aspartic acid at CD5(47)alpha and lysine at FG2(90)alpha are involved in the function of the hemoglobin molecule, despite the fact that these positions are not located directly in the heme or the alpha-beta-contact regions.Tryptophan at C3(37)beta is located at contact between alpha(1)- and beta(2)-subunits. It is suggested that the substitution by serine might disturb the quarternary structure of the mutant hemoglobin molecule during transition from oxy-form to deoxy-form resulting in an alteration of the heme function.     

Hierarchical porosity via layer-tunnel conversion of macroporous δ-MnO2 nanosheet assemblies

This work reports the layer-tunnel conversion of porous dehydrated synthetic alkali-free δ-MnO₂ analogs prepared by exfoliation, flocculation, and heat treatment of nanosheets derived from highly crystalline potassium birnessite. High surface area porous solids result, with specific surface areas of 90–130 m² g⁻¹ and isotherms characteristic of both micro and macropores. The microstructures of the re-assembled floccules are reminiscent of crumpled paper where single and re-stacked nanosheets form the walls of interconnected macropores. The atomic and local structures of the floccules heat treated from 60–400 °C are tracked by Raman spectroscopy and synchrotron X-ray total scattering measurements. During heating, the nanosheets comprising the pore walls condense to form tunnel-structured fragments beginning at temperatures below 100 °C, while the microstructure with high surface area remains intact. The flocc microstructure remains largely unchanged in samples heated up to 400 °C while an increasing fraction of the sample is transformed, at least locally, to possess 1D tunnels characteristic of α-MnO₂. Cyclic voltammetry in Na₂SO₄ aqueous electrolyte reflects the nanoscale structural evolution, where intercalative pseudocapacitance diminishes with the degree of transformation. Collectively, these results demonstrate that it is feasible to tailor the materials for applications incorporating nanoporous solids and nanofluidics, and specifically imply strategies to maintain a kinetically accessible interlayer contribute to Na intercalative pseudocapacitance.

This work reports the layer-tunnel conversion of porous dehydrated synthetic alkali-free δ-MnO₂ analogs prepared by exfoliation, flocculation, and heat treatment of nanosheets derived from highly crystalline potassium birnessite.     

Low-temperature selective catalytic reduction of NO with NH3 over an FeOx/β-MnO2 composite

A series of Fe-modified β-MnO₂ (FeO_x/β-MnO₂) composite catalysts were prepared by an impregnation method with β-MnO₂ and ferro nitrate as raw materials. The structures and properties of the composites were systematically characterized and analyzed by X-ray diffraction, N₂ adsorption–desorption, high-resolution electron microscopy, temperature-programmed reduction of H₂, temperature-programmed desorption of NH₃, and FTIR infrared spectroscopy. The deNO_x activity, water resistance, and sulfur resistance of the composite catalysts were evaluated in a thermally fixed catalytic reaction system. The results indicated that the FeO_x/β-MnO₂ composite (Fe/Mn molar ratio of 0.3 and calcination temperature of 450 °C) had higher catalytic activity and a wider reaction temperature window compared with β-MnO₂. The water resistance and sulfur resistance of the catalyst were enhanced. It reached 100% NO conversion efficiency with an initial NO concentration of 500 ppm, a gas hourly space velocity of 45 000 h⁻¹, and a reaction temperature of 175–325 °C. The appropriate Fe/Mn molar ratio sample had a synergistic effect, affecting the morphology, redox properties, and acidic sites, and helped to improve the low-temperature NH₃-SCR activity of the composite catalyst.

A series of Fe-modified β-MnO₂ (FeO_x/β-MnO₂) composite catalysts were prepared by an impregnation method with β-MnO₂ and ferro nitrate as raw materials.     

Electrophilic halogenations of propargyl alcohols: paths to α-haloenones, β-haloenones and mixed β,β-dihaloenones

The Meyer–Schuster rearrangement of propargyl alcohols or alkynols leading to α,β-unsaturated carbonyl compounds is well known. Yet, electrophilic halogenations of the same alkynols and their alkoxy, ester and halo derivatives are inconspicuous. This review on the halogenation reactions of propargyl alcohols and derivatives intends to give a perspective from its humble direct halogenation beginning to the present involving metal catalysis. The halogenation products of propargyl alcohols include α-fluoroenones, α-chloroenones, α-bromoenones and α-iodoenones, as well as β-haloenones and symmetrical and mixed β,β-dihaloenones. They are, in essence, tri and tetrasubstituted alkenes carrying halo-functionalization at the α- or β-carbon. This is a potential stepping stone for further construction towards challenging substituted alkenones via Pd-catalysed coupling reactions.

This review highlights the development of α-haloenone, β-haloenone and mixed β,β-dihaloenone formations from propargyl alcohols via direct electrophilic halogenations and metal catalysed-halonium interception rearrangements.     

THE CELLULAR ORIGIN OF HUMAN IMMUNOGLOBULINS (γ2, γ1M, γ1A)

A study was made of the cellular origin of human immunoglobulins (γ₂, γ_1M, γ_1A). The results indicated that two closely related families of cells form immunoglobulins in human lymphoid tissue: germinal (reticular) centers and plasma cells. Thus their cellular origin in addition to their known antigenic relations further justifies placing the immunoglobulins in one family of proteins. Immunoglobulins were also formed to a small extent in primitive reticular cells which resembled those of germinal centers but were separated from them. Possibly such cells were undergoing transition to the much more numerous plasma cells with which they were commonly associated. The mantles of small lymphocytes which surrounded germinal centers did not contain detectable quantities of immunoglobulins. While in general only one type of immunoglobulin was present in an individual cell or germinal center, γ₂- and γ_1M-globulin were identified on occasion in the same plasma cell and germinal center. A peculiarity of the fetal thymus gland was the presence of immunoglobulin, mainly γ_1M, in a small number of cells of small and intermediate size and primitive reticular appearance and in Hassall's corpuscles.     

Metal-free hydrosulfonylation of α,β-unsaturated ketones: synthesis and application of γ-keto sulfones

γ-Keto sulfones are versatile building blocks and valuable intermediates in organic synthesis and pharmaceutical chemistry. Motivated by their excellent properties, we herein report a green, convenient, metal-free hydrosulfonylation method for a variety of ynones, vinyl ketones, and sodium sulfinates in the absence of stoichiometric oxidants. This operationally simple protocol provides straightforward and practical access to a wide range of γ-keto sulfones with broad functional group tolerance from easily available starting materials. Moreover, the β,γ-unsaturated keto sulfones could further react with 2,3-butadienoate to generate cyclopentenes in phosphine-mediated [3 + 2] cycloaddition.

The methodology features a convenient, mild, efficient, C–S sulfonylation approach without the use of any metal catalysts and stoichiometric oxidants.

As a useful common structural fragment in a broad number of pharmaceuticals¹ and functional materials,² keto sulfones are usually present in promising biologically active molecules such as Casodex,³VCAM-1 (ref. 4) and anti-HIV-1 (ref. 5) (Fig. 1). Furthermore, a valuable synthetic impression is associated with the role of reactive intermediates in various high-demand synthetic transformations,⁶ including total synthesis.⁷ Owing to their excellent properties, and efficient and practical synthesis methods keto sulfones are in high demand.Open in a separate windowFig. 1Representative biologically active γ-keto sulfones.In the past decades, a variety of protocols have been developed to construct β-keto sulfones.⁸ Whereas succinct synthetic routes toward structurally related γ-keto sulfones are scarce,⁹ traditionally, γ-keto sulfones were synthesized via the nucleophilic substitution of sodium sulfinates by 2-chlorovinyl ketones,¹⁰ the elimination of the bromo derivatives of saturated keto sulfones¹¹ and the oxidation of the corresponding sulfides or sulfoxides.¹² However, the principal drawback is that these procedures were strongly limited by multiple steps, narrow substrate scope, or poor stereoselectivity.Indeed, several streamlined strategies for the preparation of γ-keto sulfones involves addition reaction of alkenes or alkynes have been developed.¹³ Li''s group¹⁴ reported the synthesis of (E)-vinyl sulfones through Pd-catalyzed conjugate additions of alkynes with 1,2-bis(phenylsulfonyl)ethane. In 2013 Jiang and co-workers¹⁵ showed that a Pd-catalyzed sulfonylation of alkynoates with sodium sulfinates affords γ-keto sulfones (Scheme 1a). Li and coworkers¹⁶ reported that BPO triggered the hydrosulfonylation of chalcones with arylsulfonyl hydrazides producing γ-keto sulfones. Subsequently, Bi''s group¹⁷ developed a Ag₂CO₃-promoted sulfonylation of allyl/propargyl alcohols with sodium sulfinates for the preparation of γ-keto sulfones (Scheme 1b). Nevertheless, most cases still have to use large excess oxidants, noble metal catalysts, or require high temperatures. Accordingly, an efficient, mild and practical method to furnish γ-keto sulfones is worthwhile studying.Open in a separate windowScheme 1Methods for the synthesis of γ-keto sulfones.With growing demand for sustainable chemistry, an “ideal” reaction system for such transformations would be “metal-free” due to cost efficiency and possible advantages regarding toxicity, as well as selectivity. With this intent, we herein describe a simple and efficient acid-mediated sulfonylation of sodium sulfinates and α,β-unsaturated ketones for the selective synthesis of γ-keto sulfones (Scheme 1c). The significant advantages of this method are high efficiency, metal-free and mild reaction conditions, thus providing a potential application in natural product synthesis and medicinal chemistry.Further studies were commenced with the optimization of the conditions for the hydrosulfonylation of the ynone 1f with sodium benzosulfonate 2a (13e and acetyl chloride/H₂O,¹⁹ as used in the previous study, were completely ineffective due to several unknown complex products being formed (entry 1). Gratifyingly, the desired γ-keto sulfone 3fa was isolated in a 49% yield (E/Z = 90 : 10) as the major product for the reaction mediated by AcOH (entry 3). Encouraged by this initial result, we screened an array of acids. The results showed that 4-chlorobenzoic acid (PCBA) gave the best result, leading to the isolation of γ-keto sulfone 3fa in a yield of 80% (E/Z = 98 : 02) (entries 4–15). Solvent screening indicated that mesitylene could improve the yield to 85% (E/Z = 95 : 05) (entry 21). Further investigations on the reduced usage of PCBA to 2.0 equivalents, the yield of 3fa was slightly reduced (entry 22, 83% yield, E/Z = 95 : 05). The amounts of sodium benzosulfonate 2a and the reaction temperature have deleterious effects on the reaction yields (entries 23–27). Thus, the optimized reaction conditions were successfully established as 1f (1.0 equiv.), 2a (2.5 equiv.), PCBA (2.0 equiv.), and mesitylene (2.0 mL) at 30 °C in this process.Optimization of the reaction conditions^a

Biosynthesis of 5α-Cholestan-3β-ol in Cerebrotendinous Xanthomatosis

Cerebrotendinous Xanthomatosis is a rare, inherited disease characterized by an extraordinary accumulation of cholestanol in all tissues, xanthomatous deposits in the brain, lungs, and Achilles tendons, premature atherosclerosis, and low plasma cholesterol concentrations. In two patients with the disease, the biosynthesis of cholestanol was examined by different techniques. After cholesterol-4-(14)C was injected intravenously into one patient, cholestanol and cholesterol isolated from the bile on 3 different days over the ensuing week contained significant radioactivity. The specific radioactivity-time curves for cholesterol-(14)C and cholestanol-(14)C suggested a precursor product relationship and provided additional evidence for the transformation of cholesterol into cholestanol. The second patient received intravenously a mixture of mevalonate-2-(14)C and stereospecifically labeled mevalonate-3R,4R-(3)H. Again cholesterol and cholestanol were isolated from the bile, and the (3)H/(14)C ratio in both sterols was almost the same. This experiment again demonstrated that the biosynthetic path of cholestanol proceeded through cholesterol and not directly from earlier 5alpha-H-saturated precursors. These two independent lines of evidence indicate that the extraordinary deposition of cholestanol in Cerebrotendinous Xanthomatosis arises from cholesterol presumably through the accentuation of the normal biosynthetic pathway.     

LiCl-promoted amination of β-methoxy amides (γ-lactones)

An efficient and mild method has been developed for the amination of β-methoxy amides (γ-lactones) including natural products michelolide, costunolide and parthenolide derivatives by using lithium chloride in good yields. This reaction is applicable to a wide range of substrates with good functional group tolerance. Mechanism studies show that the reactions undergo a LiCl promoted MeOH elimination from the substrates to form the corresponding α,β-unsaturated intermediates followed by the Michael addition of amines.

The amination of β-methoxy amides (γ-lactones) including natural products michelolide, costunolide and parthenolide derivatives were first developed by using lithium chloride.

The formation of carbon–nitrogen bonds remains one of the most fundamental and widely practiced reactions in organic synthesis, due to the prevalence of this functionality in the preparations of functional molecules in pharmaceutical chemistry, biochemistry and material sciences.¹ Various synthetic methodologies have been developed to form C(sp²)-N bonds, including the Goldberg reaction,² Buchwald–Hartwig reaction,³ imine reduction⁴ and the nucleophilic addition of carbon-nucleophiles to imine derivatives.⁵ Meanwhile, the formations of C(sp³)-N bonds can be achieved by reductive amination, which involves the conversion of a carbonyl group to an amine via an imine intermediate, such as Eschweiler–Clarke reaction⁶ and Borch reductive amination.⁷ Nucleophilic substitution of alkyl(pseudo)halides with amines (amine alkylation) serves as one direct strategy for the preparation of alkylamines, while the necessity of pre-installation of the halogen atoms and the production of stoichiometric inorganic salt wastes are considered as two main drawbacks for its application in large scale industrial synthesis.⁸Methoxy as the leaving group in the amination reactions has recently attracted the attention of organic chemists. For instance, Chiba and coworkers reported a method for the nucleophilic amination of methoxy arenes,⁹ which was achieved by using sodium hydride (NaH) in the presence of lithium iodide (LiI) through a concerted nucleophilic aromatic substitution pathway (Fig. 1a).¹⁰ Kondo and coworkers demonstrated that the organic superbase t-Bu-P4 efficiently catalyzes the amination of methoxy(hetero)arenes with the amine nucleophiles (Fig. 1b).¹¹ The t-Bu-P4 is also suitable to catalyze the amination of β-(hetero)arylethyl ethers with amines to synthesize β-(hetero)arylethylamines (Fig. 1c).¹² Sun and coworkers reported that C–S bond cleavage to access N-substituted acrylamide and β-aminopropanamide(Fig. 1d).¹³Open in a separate windowFig. 1Amination reactions of methyl ethers.Recently, we described the application of a CuBr–LiCl composite for the short-chain alkoxylation of aryl bromides.¹⁴ During that course of study, the single-shell lithium ion was found to embrace a unique affinity for oxygen and can be used as an additive to activate C–O bond and facilitate the nucleophilic reaction. On the basis of this study, we herein present the synthesis of β-amino amides (γ-lactones) via the elimination of methoxy group followed by Michael addition of an amine, that was promoted by LiCl in good yields under conventional conditions.We initiated our study with the reaction of 3-methoxy-N-phenylpropanamide 1a and piperidine 2a in the presence of lithium salts ( EntryAdditive (equiv.)Solvent T (°C)Time (h)Yield^b (%)1LiCl (2.0) ⁱPrOH12012702LiBr (2.0) ⁱPrOH12012303LiI (2.0) ⁱPrOH12012434LiOTf (2.0) ⁱPrOH12012385Li₂CO₃ (2.0) ⁱPrOH1201266NaCl (2.0) ⁱPrOH12012N. R.7LiCl (2.0)DMF12012468LiCl (2.0)Toluene12012219LiCl (1.0) ⁱPrOH120123810^c— ⁱPrOH12012N. R.11LiCl (2.0) ⁱPrOH80122312LiCl (2.0) ⁱPrOH120649Open in a separate window^aReaction conditions: 1a (0.45 mmol), 2a (0.90 mmol) and additive (2.0 equiv.) in solvent (3.0 mL) at 120 °C in sealed tube.^bYield of isolated product.^cNo LiCl was used.With the optimized condition in hand, the substrate scope and functional group tolerance of the transformation was then examined (Scheme 1). It was found that the 3-methoxy-N-arylpropanamides without substitution or substituted with electron-donating (–OMe) or electron-withdrawing (–Cl, –Br) groups at the para-position of the N-aryl ring exhibit good tolerance under the present conditions, giving good yields of 70–77% (3aa–3da). Moreover, the diversity of amines was studied, including pyrrolidine, diethyl amine, dimethyl amine, morpholine and methyl amine solution, and the amination products were formed in moderate to good yields in all cases (3ab–3db, 3ac–3dc, 3ad–3dd, 3ae–3de, 3af). However, when using anilin (2g) as the starting material, no reaction took place. Replacement of the N-phenyl substituent with a benzyl group (1e) led to an increased yield of 83% (3ed). Remarkably, challenging 3-methoxypropanoyl piperazine derivatives also worked well under the optimized conditions, producing the desired products in good yields (3fa–3fe). Promoted by the successful amination of the amide, we then extended this transformation to β-methoxy γ-lactones. It was noteworthy to find that 3-methoxymethyl γ-lactones 4a also worked for this reaction with the high yield of 85% 5ad.Open in a separate windowScheme 1Evaluation of the substrate scope of β-methoxy amides and amines. ^aReactions were carried out with 1a (1.0 equiv.), 2a (2.0 equiv.) and LiCl (2.0 equiv.) in ⁱPrOH (0.15 M) at 120 °C for 12 h in sealed tube. Yields of isolated products are given.Encouraged by the above results, our research was then extended to perform this transformation between the natural product michelolide derivatives 4b with β-methoxy γ-lactone subunit and various amines 2 (Scheme 2).¹⁵ Due to a high tolerance and compatibility of function groups, this strategy can be applied to 4b possessing both hydroxy group and carbon–carbon double bond. Both cyclic amines (2a, 2b, 2e, 2h) and linear amines (2d, 2i, 2f, 2j) gave the corresponding products in moderate to excellent yields. Additionally, the structure of product 5bb was unambiguously identified by X-ray crystallography.Open in a separate windowScheme 2Evaluation of the substrate scope of amines with michelolide derivatives. ^aReactions were carried out with 4b (1.0 equiv.), 2 (2.0 equiv.) and LiCl (2.0 equiv.) in ⁱPrOH (0.15 M) at 120 °C for 5 h in sealed tube. Yields of isolated products are given. ^bReaction was conducted for 10 h. ^cReaction was conducted for 20 h. ^dReaction was conducted for 15 h.Meanwhile, it is well demonstrated that amine substituted natural products is an efficient hydrophilic modification strategy used in medicinal chemistry.¹⁶ Therefore, this system was then extended to the amination of other natural product derivatives (4c–4g) containing β-methoxy γ-lactone subunit (17 Arglabin derivative 4c underwent the amination to give the product (5cd) in 99% yield, which is equivalent to the commercially available antitumor agent Arglabin-DMA.^16a,18 Michelolide derivative (4d and 4e) gave similarly good yields, in which the epoxy subunit does not affect the yield under the optimized conditions.¹⁹ The costunolide derivative 4f was converted to the corresponding product 5fd in 60% yield, while the reaction based on the parthenolide derivative 4g gave the desired product 5gd in 48% yield.Evaluation of the substrate scope of β-methoxy γ-lactones of natural products^a

Decarboxylative aldol reaction of α,α-difluoro-β-ketocarboxylate salt: a facile method for generation of difluoroenolate

We developed a decarboxylative aldol reaction using α,α-difluoro-β-ketocarboxylate salt, carbonyl compounds, and ZnCl₂/N,N,N′,N′-tetramethylethylenediamine. The generation of difluoroenolate proceeded smoothly under mild heating to provide α,α-difluoro-β-hydroxy ketones in good to excellent yield (up to 99%). The α,α-difluoro-β-ketocarboxylate salt was bench stable and easy to handle under air, which realizes a convenient and environmentally friendly methodology for synthesis of difluoromethylene compounds.

A ZnCl₂/N,N,N′,N′-tetramethylethylenediamine complex promoted decarboxylative aldol reaction of α,α-difluoro-β-ketocarboxylate salt with carbonyl compounds has been developed.     

Al-doped α-MnO2 coated by lignin for high-performance rechargeable aqueous zinc-ion batteries

Zn/MnO₂ batteries, one of the most widely studied rechargeable aqueous zinc-ion batteries, suffer from poor cyclability because the structure of MnO₂ is labile with cycling. Herein, the structural stability of α-MnO₂ is enhanced by simultaneous Al³⁺ doping and lignin coating during the formation of α-MnO₂ crystals in a hydrothermal process. Al³⁺ enters the [MnO₆] octahedron accompanied by producing oxygen vacancies, and lignin further stabilizes the doped Al³⁺via strong interaction in the prepared material, Al-doped α-MnO₂ coated by lignin (L + Al@α-MnO₂). Meanwhile, the conductivity of L + Al@α-MnO₂ improves due to Al³⁺ doping, and the surface area of L + Al@α-MnO₂ increases because of the production of nanorod structures after Al³⁺ doping and lignin coating. Compared with the reference α-MnO₂ cathode, the L + Al@α-MnO₂ cathode achieves superior performance with durably high reversible capacity (∼180 mA h g⁻¹ at 1.5 A g⁻¹) and good cycle stability. In addition, ex situ X-ray diffraction characterization of the cathode at different voltages in the first cycle is employed to study the related mechanism on improving battery performance. This study may provide ideas of designing advanced cathode materials for other aqueous metal-ion batteries.

Al³⁺ doping combined with lignin coating improves the structural stability and electrochemical performance of the modified α-MnO₂, L + Al@α-MnO₂.     

Optical and dielectric properties of NaCoPO4 in the three phases α, β and γ

In this work, we are interested in the synthesis of monophosphate α-NaCoPO₄, β-NaCoPO₄ and γ-NaCoPO₄ compounds by mechanochemical method and their characterization by X-ray powder diffraction patterns. These compounds are crystallized in the orthorhombic, hexagonal and monoclinic system, in Pnma, P6₅ and P2₁/n space groups, respectively. The optical properties were measured by means of the UV-vis absorption spectrometry in order to deduce the absorption coefficient α and optical band gap E_g. The calculated values of the indirect band gaps (E_gi) for three samples were estimated at 4.71 eV, 4.63 eV and 3.8 for compounds α, β and γ, respectively. The Tauc model was used to determine the optical gap energy of the synthesized compounds. Then, the results of the dielectric proprieties measured by varying the frequency are described.

In this work, we are interested in the synthesis of monophosphate α-NaCoPO₄, β-NaCoPO₄ and γ-NaCoPO₄ compounds by mechanochemical method and their characterization by X-ray powder diffraction patterns.     

Improvement of O2 adsorption for α-MnO2 as an oxygen reduction catalyst by Zr4+ doping

Zr⁴⁺ doped α-MnO₂ nanowires were successfully synthesized by a hydrothermal method. XRD, SEM, TEM and XPS analyses indicated that Mn³⁺ ions, Mn⁴⁺ ions, Mn^4+δ ions and Zr⁴⁺ ions co-existed in the crystal structure of synthesized Zr⁴⁺ doped α-MnO₂ nanowires. Zr⁴⁺ ions occupied the positions originally belonging to elemental manganese in the crystal structure and resulted in a mutual action between Zr⁴⁺ ions and Mn³⁺ ions. The mutual action made Mn³⁺ ions tend to lose their electrons and Zr⁴⁺ ions tend to get electrons. Cathodic polarization analyses showed that the electrocatalytic activity of α-MnO₂ for oxygen reduction reaction (ORR) was remarkably improved by Zr⁴⁺ doping and the Zr/Mn molar ratio notably affected the ORR performance of the air electrodes prepared by Zr⁴⁺ doped α-MnO₂ nanowires. The highest ORR current density of the air electrodes prepared by Zr⁴⁺ doped α-MnO₂ nanowires in alkaline solution appeared at Zr/Mn molar ratio of 1 : 110, which was 23% higher than those prepared by α-MnO₂ nanowires. EIS analyses indicated that the adsorption process of O₂ molecules on the surface of the air electrodes prepared by Zr⁴⁺ doped α-MnO₂ nanowires was the rate-controlling step for ORR. The DFT calculations revealed that the mutual action between Zr⁴⁺ and Mn³⁺ in Zr⁴⁺ doped α-MnO₂ nanowires enhanced the adsorption process of O₂ molecules.

O₂ adsorption was enhanced after doping Zr⁴⁺ into MnO₂ nanowires subsequently led to the improvement of ORR catalytic performance.     

Oxidative desulfurization of dibenzothiophene catalyzed by α-MnO2 nanosheets on palygorskite using hydrogen peroxide as oxidant

Palygorskite (Pal)-supported α-MnO₂ nanosheets (Ns-MnPal) combine the adsorption features of Pal with the catalytic properties of α-MnO₂ nanosheets. They were prepared and examined in the catalytic oxidative desulfurization (ODS) of dibenzothiophene (DBT) from a model oil employing 30 wt% H₂O₂ as the oxidant under mild conditions. The supported catalyst was fabricated by the solvothermal method, and effective immobilization of α-MnO₂ nanosheets was confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and N₂ adsorption. The influence of various solvents, solvent volume, reaction temperature, reaction time, catalyst amount and H₂O₂/sulfur molar ratio on ODS was investigated. Using 20 mL of acetonitrile as a solvent, maximum sulfur removal of 97.7% was achieved for ODS of DBT in 1.5 h using a Ns-MnPal/oil ratio of 0.2 g L⁻¹, reaction temperature of 50 °C and H₂O₂/sulfur molar ratio of 4. As solid catalysts, supported α-MnO₂ nanosheets could be separated from the reaction readily. The catalyst was recycled seven times and showed no significant loss in activity.

Palygorskite (Pal)-supported α-MnO₂ nanosheets (Ns-MnPal) combine the adsorption features of Pal with the catalytic properties of α-MnO₂ nanosheets.     

Development of γG, γA, γM, β1C/β1A, C′1 esterase inhibitor, ceruloplasmin, transferrin, hemopexin, haptoglobin, fibrinogen, plasminogen, α1-antitrypsin, orosomucoid, β-lipoprotein, α2-macroglobulin, and prealbumin in the human conceptus

The synthesis of γG, γA, γM, β_1C/β_1A, C′1 esterase inhibitor, ceruloplasmin, transferrin, hemopexin, haptoglobin, fibrinogen, α₁-antitrypsin, orosomucoid, β-lipoprotein, α₂-macroglobulin, and prealbumin was studied in 15 normal human embryos and fetuses of 29 days to 18 wk gestation and in the yolk sacs of four embryos from 5.5 to 11.5 wk gestation using tissue culture in ¹⁴C-labeled amino acids followed by radioimmunoelectrophoresis. The human embryo as early as 29 day gestation synthesized β_1C/β_1A, C′1 esterase inhibitor, transferrin, hemopexin, α₁-antitrypsin, β-lipoprotein, α₂-macroglobulin, and prealbumin in culture. At 32 days gestation ceruloplasmin and orosomucoid were also synthesized, but synthesis of fibrinogen was not observed before 5.5 wk. Synthesis of γM occurred as early as 10.5 wk gestation, and γG synthesis was found in cultures as early as 12 wk gestation; γA synthesis was not detected in any of the tissue cultures. With the exception of the γ-globulins, each of the proteins studied was synthesized by the liver, but additional sites of synthesis for some of these proteins were also found. Synthesis of γG and γM occurred primarily in the spleen, but other sites of synthesis were noted as well.