Facile preparation of α-MnO2 nanowires for assembling free-standing membrane with efficient Fenton-like catalytic activity

Assembling MnO₂ nanowires into macroscopic membrane is a promising engineered technology for catalyst separation and enhancement of Fenton-like reaction activity, yet its development is limited by the deficiencies in preparation and property modulation of the MnO₂ nanowires. In this work, we developed a facile method using C₂H₅OH and CH₃COOK as reductive and vital control reagents to react with KMnO₄ by hydrothermal reaction at 140 °C for 12 h, to prepare the ultralong α-MnO₂ nanowires up to tens of micrometers with high purity and aspect ratio. Such strategy not only had the advantages of being mild, easily controlled and environmental pollution-free, but also endowed α-MnO₂ nanowires with excellent ability as a Fenton catalyst when assembled into free-standing membrane for degrading phenolic compounds (k_obs = 0.0738 ～ 0.1695 min^?1) in a continuous flow reaction. The reactive oxygen species (i.e., ^?OH) from Fenton-like reaction were enriched within this α-MnO₂ nanowire membrane via nanoconfinement effect, which further enhanced the mass transportation of ^?OH available for phenolic contaminants. MnO₂ nanowire membrane using our method possessed the high practical potential for water purify due to its easy-preparation and enhanced catalytic performances.     

The particle dimension controlling synthesis of α-MnO2 nanowires with enhanced catalytic activity on the thermal decomposition of ammonium perchlorate

Hydrothermal method synthesis of α-MnO₂ nanowires has been achieved at different temperatures in this work. X-ray diffraction and transmission electron microscopy confirmed the pure phase of the α-MnO₂ nanowires. All of the samples crystallized in a single-phase nanowires shape. The α-MnO₂ nanowires diameter increased from 11 nm to 21 nm with the increase in hydrothermal temperature from 120 °C to 200 °C. The α-MnO₂ catalytic activity on the decomposition of ammonium perchlorate (AP) was characterized through thermogravimetric analysis. The decomposition rate of AP with the addition of α-MnO₂ was size relative. The 11 nm MnO₂ nanowires exhibited the best catalytic activity, which lowered the high-temperature peak of AP by 130 °C.     

A novel chemical route to SiO_2 nanowires

A white substance was got by directly heating TiSi powder on Ti foil, under Ar+O2 atmosphere. ED, EDX, SEM and HRTEM studies reveal that the white substance consists of amorphous SiO2nanowires of smooth surface and uniform diameter (40-90 nm). X-ray-induced luminescent emission experiment shows that two broad peaks are at 430 and 570 nm. A one-dimensional growth mechanism, on the basis of the one-dimensional thermal flow during nanowire formation, is discussed.     

Polymorph-tuned synthesis of α- and β-Bi2O3 nanowires and determination of their growth direction from polarized Raman single nanowire microscopy

We report polymorph-tuned synthesis of α- and β-Bi(2)O(3) nanowires and their single nanowire micro-Raman study. The single crystalline Bi(2)O(3) nanowires in different phases (α and β) were selectively synthesized by adjusting the heating temperature of Bi precursor in a vapor transport process. No catalyst was employed. Furthermore, at an identical precursor evaporation temperature, α- and β- phase Bi(2)O(3) nanowires were simultaneously synthesized along the temperature gradient at a substrate. The growth direction of α-Bi(2)O(3) nanowires was revealed by polarized Raman single nanowire spectra. For thin β-Bi(2)O(3) nanowires with a very small diameter, the polarized Raman single nanowire spectrum was strongly influenced by the shape effect.     

New general synthesis of α-alkoxyketones via α'-alkylation, α-alkylation and α,α'-dialkylation of α-alkoxyketimines

α-Methoxy- and α-ethoxyketones, as important intermediates in organic synthesis and flavor compounds in food chemistry, were synthesized by deprotonation of N-(1-alkoxy-2-propylidene)isopropylamine, prepared by condensation of the corresponding α-alkoxyacetone with isopropylamine, and subsequent reaction of the corresponding 1-azaallylic anions with alkyl halides to afford α'-alkylated, α-alkylated and α,α'-dialkylated ketimines. Hydrolysis of the imino function led to the desired substituted α-alkoxyketones. The ratio of α-, α'-, and α,α'-(di)alkylated compounds depended on the amount of base used and on the nature of the alkylating reagent.     

β-Ga2O3 nanowires sheathed with boron nitrogen

A new synthetic route was developed to obtain β-Ga₂O₃ nanowires by heating mixed B and Ga₂O₃ powder precursor at 1600 °C under Ar atmosphere. The nanowires have widths of 30–60 nm and perfect crystallinity. When the heating of B and Ga₂O₃ powder precursor was carried out in N₂ atmosphere, β-Ga₂O₃ nanowires sheathed with BN layers (3–5 nm) were yielded. The structure and composition of the products were characterized. The growth scenario for the β-Ga₂O₃ nanowires as well as the formation of outer BN sheaths was also discussed.     

Synthesis of New α-Heterocyclic α-Aminophosphonates

α-heterocyclic α-aminophosphonates were obtained in good yields by N-of several nitrogen heterocycles with α-azido-α-aminophosphonate 1. ¹ Elachqar, A., El Hallaoui, A., Roumestant, M. L. and Viallefont, Ph. 1994. Synthetic Comm, 24: 1279 [CSA][Taylor & Francis Online], [Web of Science ®] , [Google Scholar]     

Click-chemistry approach to isoxazole-containing α-CF3-substituted α-aminocarboxylates and α-aminophosphonates

A convenient strategy for the synthesis of isoxazole-containing α-CF(3)-substituted α-aminocarboxylates and α-aminophosphonates have been developed. The method is based on copper-catalyzed 1,3-dipolar cycloaddition of different aromatic nitrile oxides to functionalized acetylenes.     

Synthesis of new α-hydroxyphosphonates and α-acetoxyphosphonates

A series of new α-hydroxyphosphonate (5–14) have been synthesized in high yields by reaction of β-chloro-α,β-unsaturated aldehydes (1–4) and trialkyl phosphite in the presence of chlorotrimethylsilane at room temperature under solvent-free conditions. In addition, compounds (5–14) were reacted with acetic anhydride in DBU to give the new α-acetoxyphosphonate derivatives (15–23). All these phosphonates (5–23) were obtained as mixtures of two (E and Z) isomers and fully characterized by multinuclear (¹H, ¹³C, and ³¹P) NMR, IR spectroscopy and HRMS.     

Organocatalytic synthesis of α-hydroxy and α-aminophosphonates

A new and highly flexible procedure is described for the synthesis of α-amino- and α-hydroxy phosphonates. In the presence of a catalytic amount of oxalic acid (10 mol %), trimethyl phosphite reacts with aldehydes or imines (generated in situ from an aldehyde and an amine) to yield the corresponding coupled products in good yield.     

Synthesis of new racemic α-heterocyclic α,α-diaminoesters and α-aminoester carboxylic

New racemic α-aminoester and α,α-diaminoesters derivatives were synthesized by nucleophilic substitution of methyl α-azido glycinate N-benzoylated with 3-amino-1,2,4-triazole, 2-tetrahydrofuran-2-ylmethan-amine and 2-methyl quinolin-4-amine.     

Convenient synthesis of α-diarylmethylphosphonates by HOTf catalyzed Friedel-Crafts arylation of α-aryl α-hydroxyphosphonates

We report a convenient catalytic Friedel-Crafts arylation of α-aryl α-hydroxyphosphonates with various (hetero)aromatic compounds. HOTf (trifluoromethanesulfonic acid) is identified to be the best Brønsted acid catalyst, and the desired α-diarylmethylphosphonates were obtained in up to 41–95% yield.     

Two-fragment α-adrenolytics

Dialkyl β-(2-aroxyethylamino)ethylphosphonates,N-[β-(2-methoxyphenoxy)ethyl]-N′-[β-(diethoxyphosphoryl)ethyl]-α,ω-diaminoalkanes, and diethyl β-(N-arylpiperazino)ethyl-phosphonates were synthesized by the reactions of dialkyl vinylphosphonates with β-aroxyethylamines,N-[β-(2-methoxyphenoxy)ethyl]-α,ω-diaminoalkanes, andN-aryl-piperazines, respectively. The compounds synthesized exhibit hypotensive and α-adrenolytic activities. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 987–991, May 1999.     

Palladium-catalyzed Hiyama couplings of α-silylenoates and α-silylenamides

The Hiyama couplings of both α-silylenoates and α-silylenamides are described. These sensitive substrate classes require particularly specific conditions, employing both appropriate silicon-based species and a silver additive to realize high yields of the coupling products. Regioselective platinum-catalyzed hydrosilylations provide a direct and convenient entry into these stereodefined trisubstituted alkenes.     

Conformational studies on peptides containing α,α-disubstituted α-amino acids: chiral cyclic α,α-disubstituted α-amino acid as an α-helical inducer

Four types of α,α-disubstituted amino acids {i.e., α-aminoisobutyric acid (Aib), 1-aminocyclopentanecarboxylic acid (Ac(5)c), (3S,4S)-1-amino-(3,4-dimethoxy)cyclopentanecarboxylic acid [(S,S)-Ac(5)c(dOM)] and its enantiomer (R,R)-Ac(5)c(dOM)} were introduced into l-leucine-based hexapeptides and nonapeptides. The dominant conformations of eight peptides: Cbz-(L-Leu-L-Leu-dAA)(2)-OMe [dAA = 1: Aib; 2: Ac(5)c; 3: (S,S)-Ac(5)c(dOM); 4: (R,R)-Ac(5)c(dOM)] and Boc-(L-Leu-L-Leu-dAA)(3)-OMe [dAA = 5: Aib; 6: Ac(5)c; 7: (S,S)-Ac(5)c(dOM); 8: (R,R)-Ac(5)c(dOM)], were investigated by IR, CD spectra and X-ray crystallographic analysis. The CD spectra revealed that Aib hexapeptide 1 and Ac(5)c hexapeptide 2 formed right-handed (P) 3(10)-helices, while Ac(5)c(dOM) hexapeptides 3 and 4 formed a mixture of (P) 3(10)- and α-helices. The Aib nonapeptide 5 formed a (P) 3(10)-helix, the Ac(5)c nonapeptide 6 formed a mixture of (P) 3(10)- and α-helices, and the Ac(5)c(dOM) nonapeptides 7 and 8 formed (P) α-helices. X-Ray crystallographic analysis revealed that the Aib hexapeptide 1 formed a (P) 3(10)-helix, while (S,S)-Ac(5)c(dOM) hexapeptide 3 formed a (P) α-helix. In addition, the Ac(5)c nonapeptide 6 and (R,R)-Ac(5)c(dOM) nonapeptide 8 formed (P) α-helices. The Aib and achiral Ac(5)c residues have the propensity to form 3(10)-helices in short peptides, whereas the chiral Ac(5)c(dOM) residues have a penchant for forming α-helices.     

Two-fragment α-adrenolytics

A method for the synthesis of hypotensive alkyl(phenyl)[ω-(N-phenylpiperazino)alkyl]-phosphine oxides by reacting alkyl(ω-haloalkyl)phenylphosphine oxides withN-phenylpiperazine was elaborated. Phenyl[γ-(N-phenylpiperazino)propyl]propylphosphine oxide reacts with alkyl halides to give [γ-(N-alkyl-N′-phenylpiperazinio)propyl]phenyl(propyl)oxophosphine halides. For Part 1 see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 488–492, March, 2000.     

Two-fragment α-adrenolytics

Primary alkylamines, β-aryloxyethylamines, orN-[β-(2-methoxyphenoxy)ethyl]-α,ω-diaminoalkanes react with alkyl divinyl phosphinates or phenyl(divinyl)phosphine oxide to give the corresponding 4-alkoxy(4-phenyl)-1-alkyl-4-oxo-1,4-azaphosphorinanes. Reactions of the latter with mono- or dihaloalkanes afford 4-phosphapiperidinium halides. 1,4-Azaphosphorinanes containing a β-aryloxyethyl fragment exhibit hypotensive activity.