Electrocatalytic oxidative cleavage of electron-deficient substituted stilbenes in acetonitrile-water employing a new high oxidation potential electrocatalyst. An electrochemical equivalent of ozonolysis

A series of symmetrical and unsymmetrical stilbenes bearing two or more strong electron-withdrawing groups were oxidatively cleaved to the corresponding aldehydes in high yield by electrocatalytic anodic oxidation in aqueous acetonitrile employing a new high oxidation potential triphenylamine electrocatalyst. The oxidations apparently involve the corresponding 1,2-diols, which are also converted to aldehydes in high yield under the same conditions.     

Yield stress analysis of 1D calcium and titanium precipitate-based giant electrorheological fluids

1D calcium and titanium composite nanorods synthesized were applied as electrorheological (ER) active materials with extremely high static yield stresses, i.e., giant ER effect. The yield stress of this giant ER fluid was analyzed using a new universal yield stress scaling equation in the form of the modified Bessel functions with two different limiting behaviors in a low and high electric field region. The universal yield stress equation collapsed the yield stress data onto a single curve.     

氯化锆催化芳胺和正丁醛合成喹啉衍生物

以ZrCl4为催化剂,芳胺和醛为原料,采用"一锅法"合成了喹啉衍生物;考察了空气、催化剂用量、原料比例以及芳胺的取代基等因素对反应收率的影响;利用高分辨质谱和核磁共振谱(1 H NMR、13 C NMR)表征了产物的分子结构.结果表明,以苯胺和正丁醛为原料时,3-乙基-2-丙基喹啉的收率可达65%,同时生成27%的N-丁基苯胺;工艺经改进后,反应条件温和、操作简便、催化剂用量少、产物收率高.     

Preparation of Silver Nanofluids with High Electrical Conductivity

Silver nanofluids have been prepared by single-step chemical reduction method starting with silver nitrate metal precursor. Electrical conductivity of nanofluids has been investigated, as it has largely been overlooked despite immense technological importance. Extremely low yield nanofluid (0.013 wt%) is found to give high electrical conductivity attributed to smaller size monodisperse nanoparticles obtained (16.3 nm). Increased precursor concentration has lead to high yield and high electrical conductivity. Larger particle sizes obtained are optimized by reducing the yield at high concentration, as well as by dilution. The stability is exceptionally higher than the reported results for copper nanofluids.     

Reductive ring openings of allyl-alcohol epoxides

Red-Al reduction of allyl-alcohol epoxides was shown to yield 1,3-diols in high regioselectivity, while DIBAL reduction was shown to yield 1,2-diols.     

Bromination of ‘endo‐Benzocyclobutanorbornene': Synthesis of ‘endo‐ 11,12‐Dibromobenzocyclobutanorbornene': High‐Temperature Bromination,Part XIV

The electrophilic addition of Br to ‘endo‐benzocyclobutanorbornene' 5 at −50° led in high yield to the formation of the rearranged dibromides 6 and 7 . However, high‐temperature bromination of 5 in decalin at 150° gave exclusively nonrearranged product 8 in 98% yield. From the elimination of nonrearranged product 8 , ‘endo‐bromobenzocyclobutanorbornene' 9 and ‘endo‐benzocyclobutanorbornene' 5 were obtained. Similarly, bromination of monobromide 9 at 77° yielded the nonrearranged tribromide 12 in quantitative yield. The dehydrobromination of 12 provided the ‘endo 11,12‐dibromobenzocyclobutanorbornene' 3 in high yield, which is a synthon for the trimerization reactions.     

Synthesis and Reactions of 3-Halogenated 2-CF3-Indoles

Halogenation of 2-trifluoromethylindole afforded 3-chloro-, 3-bromo- and 3-iodo derivatives in up to 98% yield. Methyl-, benzyl- and tosyl-groups can be installed at the nitrogen atom of prepared indoles in high yields by base catalyzed reaction with the corresponding alkylating (sulfonylating) reagents. A high synthetic utility of the prepared haloindoles in the reaction with various nucleophilies was shown. The reaction with 4-methylthiophenol and copper cyanide afforded the corresponding sulfides and nitriles in high yield. Palladium catalyzed cross-coupling with phenyl boronic acid and phenylacetylene gave the corresponding 3-phenyl-2-CF₃-indoles and acetylenic derivatives in 72–98% yield.     

弱碱作用下从叔醇简便地合成烯烃

用甲磺酸酐和三乙胺作为脱水剂, 发展了一种从叔醇合成烯烃的简便方法, 反应时间短, 温和的条件和高产率使该方法可以快速地从叔醇合成烯烃.     

Diastereoselection in the nucleophilic conjugate addition of amines to 2-hydroxyalkylpropenoates

Nucleophilic conjugate addition of benzylamine to 2-hydroxyalkylpropenoates 1a-c proceeds in high yield with modest diastereoselection. However, addition of benzylamine to the silyl ether of 1c produces only the anti-isomer 2d in high yield.     

A high yield route to ethyl esters of car☐ylic acids

Diethyl trichloromethylphosphonate reacts with car?ylic acids to yield their ethyl esters, via transesterification; even the hindered mesitoic acid is esterified in high yield.     

Ring contracting sulfur extrusion from oxidized phenothiazine ring systems

Lithium, used in conjunction with sodium metal, produces a high yield of carbazole when reacted with phenothiazine-5-oxide or phenothiazine-5,5-dioxide. A high yield of 9-ethylcarbazole is also produced when these reagents react with 10-ethylphenothiazine, 10-ethylphenothiazine-5-oxide, and 10-ethylphenothiazine-5,5-dioxide. Degassed Raney nickel produces carbazole in high yield when reacted with phenothiazine and phenothiazine-5-oxide. A moderate yield of 9-ethylcarbazole is produced when n-butyllithium is reacted with 10-ethylphenothiazine-5-oxide.     

Diphenyl cyanocarbonimidate. A versatile synthon for the construction of heterocyclic systems

A simple high yield synthesis of diphenyl cyanocarbonimidate is reported. This synthon may be used to prepare functionalized benzimidazoles, benzoxazoles and triazoles in good yield under mild conditions.     

Synthesis and characterization of highly fluorinated diamines and benzoxazines derived therefrom

A novel method for the synthesis of highly fluorinated benzoxazines in a high yield derived form a α,ω-diamine-polyfluoroalkane and α,ω-dianiline-polyfluoroalkane is described. The synthetic method increases the yield by 20% and reduces the reaction time by 90% in comparison to the currently known method, allowing synthesis of large quantity of highly fluorinated diamines. The diamines are used as the precursors for benzoxazine compounds. The diamines and benzoxazines are obtained in high yield and purity. The structures are characterized by nuclear resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FT-IR).     

Product-Specific Methods of Syntheses of Hexaphenylcyclotrisiloxane and Octaphenylcyclotetrasiloxane — Monomers of Phenylsilicones

Pure hexaphenylcyclotrisiloxane (P₃) and octaphenylcyclotetrasiloxane (P₄) were synthesized with high yields via proper choice of preparation conditions, such as catalysts, solvents and reaction temperatures, from diphenylsilanediol. Up to 98% yield of this pure starting material can be obtained from diphenyldi-chlorosilane through modifying a known procedure on carefully adjusting the temperature of hydrolysis and washing procedure. This method produced pure P₃ exclusively with high yield (approximately 90%) in ethanol in the presence of concentrated sulfuric acid as the catalyst at various reaction temperatures. P₄ was produced exclusively in high yield (approximately 90%) in alcohols in the presence of sodium hydroxide. A method applying HPLC was used to analyze the reaction products quantitatively.     

A convenient preparation of 2-fluoro-3-alkoxy-1,3-butadienes

[reaction: see text] 1-Chloro-1-fluoro-2-methoxy-2-methylcyclopropane eliminates HCl on heating in quinoline solution above 50 degrees C to give 2-fluoro-3-methoxy-1,3-butadiene in high yield. If an alcohol is added to the reaction then a 2-fluoro-3-alkoxy-1,3-butadiene is obtained in high yield. The dienes give smooth 4 + 2 cycloaddition reactions.     

Conjugate addition of amines to chiral 3-aziridin-2-yl-acrylates

Conjugate addition of benzylamine to chiral methyl cis-3-aziridin-2-yl-acrylates was successfully proceeded to yield 3-aziridin-2-yl-3-benzylaminopropionates in high yield with high stereoselectivity. The addition products were used for the asymmetric synthesis of vicinal diamine derivatives including 4-amino-5-methylpyrrolidin-2-one, 3,4-diaminopentanoate, and 5-chloromethyl-4-alkoxycarbonylmethylimidazolidin-2-one.     

Efficient synthesis of (S,S)-2,8-diazabicyclo[4.3.0]nonane

An efficient synthetic route for moxifloxacin chiral intermediate via five steps was established. First, dehydration, N-acylation, and cyclization were combined in one pot to meet the industrial requirement. Then relatively low hydrogen pressure was employed in the catalytic hydrogenation reaction with high yield. Isopropanol/water system was used in resolution, which guaranteed high yield and perfect optical purity. The racemic process conducted by manganese dioxide and Pd/C successfully converted the undesired enantiomer into the racemate and hence the total yield increased remarkably. Furthermore, mild hydrogen transfer catalytic hydrogenation method was utilized in debenzylation process instead of high-pressure hydrogenation. Total yield of 39.0% was achieved, which was much higher than that of 29.0% in literature.     

An Efficient Synthesis of Dicyclohexylmethyl Diazoacetate

Oiazoacetateisaversatilereagentinorganicsynthesis'.Ithasbeenwidelyusedincyclopropanation.etheration.elc.Bothenantiomericselectivityanddiastereoselectivit}ofcyclopropanationaregreatlyaffectedbyalkylgroupofalkyldiazoacetate.Highselectivitieswereobtainedusingstericdemandingdiazoacetate.Aratallihasusedmenth}'jdiazoacetate(MnDA)=.andDoylehasemployed2.6-di-lerl-butyl-4meth\lphenyldiazoacetate3toachievehighselectivities.Masamunefoundthatdicyclohexylmethyldiazoacetate(DCHMDA)wassuperiortotheabove…     

Eco-friendly synthesis of 2-substituted-2,3-dihydro-4(1H)-quinazolinones in water

2-Substituted-2,3-dihydro-4(1H)-quinazolinones were synthesized in high yield by condensation of 2-anthranilamide with aromatic aldehydes or ketones in refluxing water without catalyst.This protocol has advantages of high yield,simple work-up and environmental friendly procedure.     

烯酮缩胺与芳基异硫氰酸酯的反应: 合成异噻唑化合物 的一个途径

具有不同取代基的五状和非环状的烯酮缩胺与芳基异硫氰酸酯在两酮中回流,可高产率地获得α-碳加成产物,该产物在溴存在下可氧化关环生成异噻唑类化合物。