Reduction of beta-hydroxyketones by SmI2/H2O/Et3N

Reduction of a series of beta-hydroxyketones by SmI2/H2O/Et3N provided 1,3-diols in quantitative yields. The reactions were exceedingly clean with no byproduct formation, negating the need for further purification. Most reactions provided moderate to excellent diastereoselectivity with syn-diols as the major isomer in most instances.     

Synthesis of 6-methyl-8H-dibenzo[a,g]quinolizin-8-imines via Reissert compounds

Alkylation of Reissert compounds derived from 3-methylisoquinolines with several 2-cyanobenzylbromides followed by hydrolytic cleavage provided the corresponding 1-benzyl-3-methylisoquinolines. Treatment of the latter with methylmagnesiumiodide caused cyclization to the title compounds rather than formation of 2-acetylbenzylisoquinolines.     

Activation of methylenetriphenylphosphorane by reaction with t-butyl- or sec-butyllithium

Experimental details are provided to support a previous report that α-methylenetriphenylphosphorane ($\text{1}$) may be activated for reaction with unreactive substrates such as epoxides and hindered ketones by α-metallation to $\text{2}$.     

Thermal behavior analysis of nickel/metal hydride battery during overcharging

To analyze the thermal behavior of the cylinder Ni/MH battery during overcharging,a two-dimensional thermal model is provided in this work.More reliable data is provided to create the precise thermal model.The amount of heat of the battery during overcharging at different currents was measured using quartz frequency microcalorimeter.To obtain the heat transfer coefficient of the battery during overcharging,the heat dissipation rate was fitted into linear functions and three different exponential functions f...     

Synthesis and absolute configuration of P-chiral O-isopropyl oligonucleotide triesters

New $\text{O}$-isopropylphosphomorpholidite reagents provided the title compounds as mixtures of P-chiral diastereomers, which were separated by HPLC for enzymatic digestion studies and assignment of configuration at phosphorus by chemical correlation with known phosphorothioates.     

Preparation and characterization of standard reference material 1849 infant/adult nutritional formula

Standard Reference Material (SRM) 1849 Infant/Adult Nutritional Formula has been issued by the National Institute of Standards and Technology (NIST) as a replacement for SRM 1846 Infant Formula, issued in 1996. Extraction characteristics of SRM 1846 have changed over time, as have NIST's analytical capabilities. While certified mass fraction values were provided for five constituents in SRM 1846 (four vitamins plus iodine), certified mass fraction values for 43 constituents are provided in SRM 1849 (fatty acids, elements, and vitamins) and reference mass fraction values are provided for an additional 43 constituents including amino acids and nucleotides, making it the most extensively characterized food-matrix SRM available from NIST.     

N-Dimethylphosphoryl-protection in the efficient synthesis of glucosamine-containing oligosaccharides with alternate N-acyl substitutions

Ready transformation of N-dimethylphosphoryl-protection into the corresponding N-acyl derivatives (in the presence of acyl chlorides and DMAP in pyridine) provided an effective approach to the synthesis of glucosamine-containing oligosaccharides with alternate N-acyl substitutions.     

Direct synthesis of dimethyl carbonate ?from CH3OH AND CO2 by H3PW12O40/CexTi1-xO2 catalyst

Summary Ce_xTi_1-xO₂ and H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ catalysts were prepared using a sol-gel method, and applied to the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ showed a better catalytic performance than the corresponding Ce_xTi_1-xO₂, due to the bifunctional catalysis of Br?nsted acid sites (provided by H₃PW₁₂O₄₀) and base sites (provided by Ce_xTi_1-xO₂). H₃PW₁₂O₄₀/Ce_0.1Ti_0.9O₂ showed the highest catalytic performance among the H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ catalysts.     

Reaction of 1-phenyldiazoethane with tetrachloro-p- and o-benzoquinones

Reaction of 1-phenyldiazoethane(1) with tetrachloro-p-benzoquinone(2) gave 1-alkoxy-4-ethenyloxy-tetrachlorobenzene(4). With tetrachloro-o-benzoquinone(5), 1 provided 1-alkoxy-2-ethenyloxy-tetrachlorobenzene(7) and tetrachlorobenzo-1,3-dioxolane(8). The mechanism and the effect of added methanol were discussed.     

Selective transformation of N-t-butoxycarbonyl group into n-alkoxy-carbonyl group via n-carboxylate ion equivalent

Reaction of a variety of N-$\text{t}$-butoxycarbonyl compounds with $\text{t}$-butyl-dimethylsilyl trifluoromethanesulfonate afforded the N-$\text{t}$-butyldimethyl-silyloxycarbonyl compounds, chemoselectively, which upon treatment with an alkyl or aryl halide provided the corresponding N-alkoxy- or N-aryl-oxycarbonyl compounds, efficiently.     

N-乙酰氨基葡萄糖水溶液变旋过程的液质联用和旋光研究

研究N-乙酰氨基葡萄糖在水溶液中的变旋行为.通过液质联用及比旋度分析,监测N-乙酰氨基葡萄糖水溶液的变旋情况.得到基于APCI离子源的N-乙酰氨基葡萄糖的多级质谱图,确认其水溶液变旋稳定时间及稳定状态下的差向异构体组成比例,并对N-乙酰氨基葡萄糖HPLC图中的差向异构体色谱峰进行指认.为存在变旋行为的糖及糖苷类化合物的研究提供了准确可行的方法.     

Crystal and Molecular Structure of trans-[Pd(Bu2S)2(NO2)2]

Single crystals of the [PdL₂(NO₂)₂] complex were obtained for the first time, where L is di-n-butylsulfide. Single crystal and powder diffraction studies provided new data on the molecular and crystal structure of this compound.     

Thermal- and photo-induced transformations of N-aryl-N-nitrosohydroxylamine ammonium salts to azoxy compounds

Heating of an ethanolic solution containing N-aryl-N-nitrosohydroxylamine ammonium salts at 78 °C produced the desired azoxy compounds in 80–93% yields. Furthermore, irradiation with UV light (λ≥300 nm) of ethanolic solutions of those ammonium salts at room temperature also provided the desired azoxy compounds in 51–72% yields.     

Synthesis of PI-88 analogue using novel O-glycosidation of exo-methylenesugars

Acid-promoted α-stereoselective O-glycosidation of 1-exo-methylenesugars was successfully applied to the synthesis of a PI-88 analogue. By using methanesulfonic acid as a promoter, 1′-C-methyl-α-disaccharides with p-methoxybenzyl protection were obtained in high yield. The sequence of selective deprotection and glycosidation provided 1-C-methyl-pentasaccharide efficiently.     

An Improved Stereocontrolled Route to cis-Erythrinanes by Combined Intramolecular Strecker and Bruylants Reaction

Condensation of (2-iodophenyl)ethylamines with cyclohexanoylacetaldehyde provided the corresponding aldimines which were reduced yielding secondary phenethylcyclohexanoylethylamines. These in turn were appropriate intermediates to prepare several erythrinanes by a sequential intramolecular Strecker and intramolecular Bruylants reaction. In contrast, the C-ring homologue schelhammeranes were not available on this route.     

Iodine catalyzes C-glycosidation of d-glucal with silylacetylene

A convenient method for C-glycosidation (alkynylation) with various silylacetylenes to d-glucal by iodine molecule via iodo-oxonium intermediates provided exclusively the α-acetylene glycoside products. Eleven successful examples are shown under this condition.     

NH4I/EtOCS2K promoted synthesis of substituted benzils from diphenylacetylene derivatives

A facile protocol is described for the synthesis of benzil derivatives from readily accessible diarylacetylene derivatives using the NH₄I/EtOCS₂K system. This novel protocol results in excellent chemoselectivity and provided good to excellent yields. A control experiment indicated that the reaction proceeds via NH₄I promoted EtOCS₂K dimerization to give the corresponding dixanthogen and subsequent dixanthogen assisted oxidation.     

Problems connected with the melting of NiII, CoII and MnII cyclo-tetraphosphates

Differential thermal analysis has been used to follow the process of melting of Ni^II, Co^II and Mn^II cyclo-tetraphosphates. The melting is congruent in a dry atmosphere, being non-congruent in the presence of small amounts of water vapour: the tetraphosphate cycles are split and further condensed to chains of higher linear phosphates. Their end groups (and hence their stability) are provided by water molecules present in the atmosphere. After cooling the products have a glassy amorphous form. By repeated heating they are changed back into the cyclo-tetraphosphates with crystalline character, and the water molecules are released.     

Enzymatic desymmetrization of meso cis,cis-2,4,6-substituted tetrahydropyrans

The stereoselective acylation of meso-tetrahydropyrans 6 and 7 by enol esters (vinyl acetate or isopropenyl acetate) in the presence of Candida antarctica lipase in organic media gave the corresponding (2R,4S,6S)-monoesters 10 and 11 in high enantiomeric purity. The hydrolysis of the corresponding diacetate derivatives 8 and 9 in the presence of the same enzyme provided the opposite enantiomers, (2S,4R,6R)-monoesters 10 and 11.     

Unprecedented dual reactivity of anhydrous potassium hydroxide in cascade cyclopropannelation/Haller-Bauer-scission/Grob-fragmentation reactions

We report an unprecedented type of reactivity of ‘anhydrous potassium hydroxide’ (‘APH’) in which it plays, over a large variety of related educts, sequentially the role of base and nucleophile. Some insight into the structure of reactive species as well as comparative reactivity of related reagents prepared by fusion of commercially available potassium hydroxide or by adding stoichiometric amount of water to potassium hydride is provided.