Synthesis of α-Nitro Ketoximes from Styrenes and tert-Butyl Nitrite

We have discovered that various α-nitro ketoximes can be synthesized in good yields starting from styrenes and tert-butyl nitrite. The success of the reaction was critically dependent on the use of a mixture solvent of dimethylsulfoxide and water. The reaction can tolerate a wide variety of substituents including electron-withdrawing and electron-donating groups.     

Dibenzylmagnesium-Initiated Anionic Oligomerizations of trans-Stilbene, 1,1-Diphenylethylene,and α-Methylstyrene in Hexamethylphosphortriamide

trans-Stilbene, 1, 1-diphenylethylene, and α-methylstyrene were allowed to react with dibenzylmagnesium to form their oligomers in hexamethylphosphortriamide (HMPA). One and two molecules of stilbene and 1, 1-diphenylethylene were incorporated into the magnesium carbon bond, and the carbanions obtained in HMPA were stable in analogy with the anionic living polymer having alkali cation as the gegenion in eithers. Intense coloration was observed during the reaction between α-methylstyrene and dibenzylmagnesium as well as in the case of stilbene and 1, 1-diphenylethylene. The low molecular weight products which were formed after a long time in the reaction between α-methylstyrene and dibenzylmagnesium were found to have no magnesium-carbon bond. It was considered that the cleavage of the propagating chain occurred gradually after the rapid propagation had proceeded to consume the monomer.     

Iron Catalyzed Isomerization of α-Alkyl Styrenes to Access Trisubstituted Alkenes

Stereoselective isomerization of α-alkyl styrenes is accomplished using a new iron catalyst supported by phosphine-pyridine-oxazoline (PPO) ligand.The protocol ...     

Tri- and tetrasubstituted α-fluorocyclohexanones with enantiomeric excesses in the range of 97–100%

The α-fluorinated trisubstituted ketones (2S,5R)-(−)-7-Ia, (2R,5R)-(+)-7-IIe, (2S,5R)-(−)-8-Ia and (2R,5R)-(+)-8-IIe were synthesised from (+)-dihydrocarvone (99% (R)-configuration at C-5) and fully characterised. α-Fluorinated tetrasubstituted ketones (−)-9-Ia, (+)-9-Ia, (+)-9-IIa and (+)-10-Ia having e.e.s of ≥97% were synthesised as racemates from 3-methyl cyclohexenone then resolved into the pure enantiomers using chiral HPLC and fully characterised.     

Purification and Characterization of Cold-active α-Amylase Excreted by A Strain of Marine Cold-adaptive Penicillia

The filamentous fungi from the Huanghai sea sludge were screened according to their ability to produce cold-active α-amylase. The strain with the highest amylase activity was identified as Penicillium species. The α-amylase purified by ammonium sulphate precipitation and column chromatography on DEAE-sepharose and sephadex G-100 shows a molecular weight of about 55000 and a pI of 4.38. The enzyme is stable in a pH range of 5.5-8.0 and has a maximum activity at pH 6.0. Compared with the α-amylase from mesophiles and thermophiles, the cold-active enzyme shows a high enzyme activity at lower temperatures and a high sensitivity at temperatures higher than 50 ℃. The optimal temperature is 40 ℃ and the activity decreases dramatically at temperatures above 50 ℃. Ca2 shows a significant effect on maintaining the structure and the activity of the enzyme. EDTA and Cu2 are its inhibitors. The products from the hydrolysis of soluble starch with the cold-active enzyme are maltose and other oligosaccharides.     

Purification and Characterization of Cold-active α-Amylase Excreted by A Strain of Marine Cold-adaptive Penicillia

The filamentous fungi from the Huanghai sea sludge were screened according to their ability to produce cold-active α-amylase. The strain with the highest amylase activity was identified as Penicilllum species. The α-amylase purified by ammonium sulphate precipitation and column chromatography on DEAE-sepharose and sephadex G-100 shows a molecular weight of about 55000 and a pl of 4. 38. The enzyme is stable in a pH range of 5.5—8.0 and has a maximum activity at pH 6.0. Compared with the α-amylase from mesophiles and thermophiles, the cold-active enzyme shows a high enzyme activity at lower temperatures and a high sensitivity at temperatures higher than 50℃. The optimal temperature is 40℃ and the activity decreases dramatically at temperatures above 50℃. Ca^2 shows a significant effect on maintaining the structure and the activity of the enzyme. EDTA and Cu^2 are its inhibitors. The products from the hydrolysis of soluble starch with the cold-active enzyme are maltose and other oligosaccharides.     

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.     

Syntheses of carbocyclic analogues of α-D-glucosamine, α-D-mannose, α-D-mannuronic acid, β-L-idosamine, and β-L-gulose

A versatile synthesis of orthogonally protected derivatives of carba-α-D-glucosamine, carba-α-D-mannose, carba-α-D-mannuronic acid, carba-β-L-idosamine, and carba-β-L-gulose from methyl α-D-mannoside is described. Our synthetic strategy utilizes the palladium-promoted Ferrier carbocyclization and persistent butane-2,3-diacetal protection to produce a key chiral cyclohexanone intermediate, from which all five carbasugar derivatives can readily be obtained.     

Regio- and Stereoselective Synthesis of 1→6 Linked Manno-, Gluco-, and Galactopyranose Di-, Tri-, and Tetrasaccharides Via Orthoester Intermediates

ABSTRACT

1→6 Linked manno-, gluco-, and galactopyranose di-, tri-, and tetrasaccharides with 1,2-trans glycosidic linkages were concisely and effectively synthesized using peracetylated glycosyl bromides as the donors and unprotected or partially protected glycopyranosides as the acceptors via orthoester intermediates.     

Synthesis of 1,2,3,5-substituted pyrroles from α-bromoacetophenones and 2-nitroethene-1,1-diamines

The simple synthesis of 1,2,3,5-substituted pyrroles from α-bromoacetophenones and 2-nitroethene-1,1-diamines in the presence of K₂CO₃ in DMF at 120 °C is described. A range of fused and non-fused polysubstituted pyrroles were prepared in high yields with short reaction times.     

Synthesis of α-alkyl- and α,α-dialkyl-β-phenyltryptamines

A new method was developed for the synthesis of -alkyl- and ,-dialkyl--phenyltryptamines based on alkylation of nitroalkanes with -phenyl-nor-gramine.     

Synthesis and characterization of α,ω-dichloro-polymethylphenylsilane

The synthesis of a functional polysilane, α,ω-dichloro-polymethylphenylsilane (α,ω-dichloro-PMPS), based on the Wurtz-type reductive coupling, has been considered. A study of some reaction parameters shows that both yield and molecular weight distribution of α,ω-dichloro-PMPS can be greatly influenced by the work-up conditions, reaction time, monomer concentration and temperature during the initiation of the polymerization. By varying the synthesis conditions, different ratios of high and low molecular weight fractions were obtained. Samples of different molecular weight were isolated by fractional precipitation of the crude polymers. The chlorine-end functionalization was confirmed by ²⁹Si NMR spectroscopy and the concentration of end-groups was quantitatively determined by elemental analysis of chlorine.     

DFT Study of Dimethylaluminum Azide Clusters： Structures,Energies, Frequencies and Thermodynamic Properties

Introduction The organoaluminum azide compounds have been widely used in many fields. These compounds are used as the azidating agents,1-3 and the energetic materials which are always used in national defence industry and in space technology, especially to generate thin films of AlN in various chemical vapor deposition (CVD) sys-tems.4-6 Aluminum nitride has useful properties for coatings, especially for optical or optoelectronic devices, acoustic wave devices and electronic microcircuits.7 …     

Synthesis and structural study of α-amino- and α,ω-diamino oligoamides-11

α-Amino (MAO) and α,ω-diamino (DAO) oligoamides were prepared using dodecylamine or 1,6 diaminohexane as a chain limitator. These were characterized by GPC, ¹H-NMR and ¹³C-NMR; molecular models: N-dodecyldodecanamide and 1,6 bis dodecylaminohexane; trifluoroacetylation was used to dissolve the oligoamides. DAO prepared in the melt contains two types of chains, depending on the position of the limitator. When oligomers were prepared in solution using the Yamazaki method, the presence of residual phosphorus derivatives in the oligoamides could not be avoided.     

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.     

Catalytic diastereoselective reduction of α,β-epoxy and α,β-aziridinyl ynones

The Noyori transfer hydrogenation of α,β-epoxy and α,β-aziridinyl ynones leads to the corresponding α,β-epoxy or α,β-aziridinyl propargylic alcohols with high reagent-controlled diastereoselectivity.     

Synthesis,Characterization, and Structures of α-Substituted Selenenyl-Acetophenones

Abstract

A series of α-substituted selenenyl acetophenone derivatives of the types, [PhC(OCH₂CH₂O)CH₂Se]₂, [PhC(OCH₂CH₂O)CH₂SeR], (PhCOCH₂Se)_2, and [PhCOCH₂SeR] have been prepared. These compounds have been characterized by elemental analyses, IR and NMR (¹H, ¹³C, ⁷⁷Se) spectroscopy. The compounds, [PhC(OCH₂CH₂)CH₂Se]₂ and (PhCOCH₂Se)₂ have been structurally characterized by single crystal X-ray diffraction analyses. The former shows intra-molecular Se‐?‐?‐O interaction, while the latter exhibits inter-molecular nonbonding Se‐?‐?‐O interaction.

[Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental files: Additional text and figures.]