Organocobalt cluster complexes X. Evidence for the methylidynetricobalt nonacarbonyl radical

The azobisisobutyronitrile-initiated addition of HCCo₃(CO)₉ to the CC bonds of allyl acetate and allyl ethyl ether to give (OC)₉Co₃C(CH₂)₃O₂CCH₃ and (OC)₉Co₃C(CH₂)₃OC₂H₅, respectively, demonstrated the accessibility of the ·CCo₃(CO)₉ radical.     

Methylidynetricobalt nonacarbonyl catalyzed cyclotrimerization of alkynes

A cobalt carbonyl cluster, methylidynetricobalt nonacarbonyl, catalyzed inter- and intramolecular cyclotrimerization of alkynes producing substituted benzene derivatives in good to excellent yields.     

Iridium complex catalyzed carbonylative alkyne-alkyne coupling for the synthesis of cyclopentadienones

[reaction: see text]. Catalytic carbonylative alkyne-alkyne coupling proceeds using iridium-phosphine complexes under carbon monoxide at atmospheric pressure or a partial pressure of 0.2 atm. This reaction provides various cyclopentadienones in high isolated yields.     

Synthesis and properties of alkoxyalkylidinetricobalt nonacarbonyl cluster complexes

The title compounds are obtained in fair to good yield by desulfurization of S-alkyl xanthates in reactions with dicobalt octacarbonyl. The cluster structure is supported by mass spectroscopic and NMR data, and evidence is presented for an elimination step leading to desulfurization. These air-stable complexes are active catalysts for hydroformylation of olefins.     

Synthesis of bis-indolylmethanes catalyzed by oxone

Oxone (3.5 mol%) was found to be an effective catalyst for the condensation reactions of indoles with aldehydes to afford bis-indolylmethanes in good to excellent yields within 10–30 min. The method is simple and economic. The catalyst is found to be recyclable.     

Synthesis of monocaprin catalyzed by lipase

The production of monoglyceride emulsifiers commonly employed in the food, cosmetic, and pharmaceutical industries can be catalyzed by lipases, biocatalysts that are becoming increasingly attractive in the enzyme market. The aim of this study was to produce monocaprin utilizing a commercial immobilized lipase (Lipozyme IM 20) through the direct esterification of capric acid and glycerol. Experiments were performed for 6 h in an open reactor and the products were analyzed by gas chromatography. The parameters investigated were the amount of enzyme, temperature, and molar ratio between the reagents (capric acid/glycerol). The experimental runs followed an experimental design generated using Statistica® software. The results showed that all the parameters were significant and that monocaprin production was enhanced at the lower ranges of the tested variables. The best conditions established were 55°C, 3% (w/w) enzyme concentration, and molar ratio of 1. The final product, obtained after 6 h of reaction, was 61.3% monocaprin, 19.9% dicaprin, and 18.8% capric acid. This composition satisfies the directives of the World Health Organization food emulsifiers, which requires that these mixtures have at least 70% mono- plus diglyceride, and a minimum of 30% monoacylglycerol.     

酶促反应合成糖脂化合物

对糖脂化合物的酶促合成研究进行了总结,其中包括有机相中和无溶剂条件下的糖脂酶促合成。     

离子液体催化合成对羟基苯甲酸乙酯

采用酸性离子液体[C3SO3 Hmim] HSO4、[C4SO3 Hmim] HSO4和[C3SO3 Hnhm] HSO4代替浓硫酸为催化剂合成对羟基苯甲酸乙醇.考察了反应温度、反应时间、催化剂用量、酸醇摩尔比对该反应产率的影响及离子液体的重复使用性能.选择了最佳反应条件,以[C3SO3 Hnhm] HSO4作为催化剂...     

Preparation of optically pure cross-conjugated cyclopentadienones

The synthesis of optically pure cross-conjugated cyclopentadienones is readily achieved in two steps via a one-pot alkylcuprate addition/aldol condensation/dehydration sequence using racemic or enantioenriched endo-3a,4,7,7a-tetrahydro-1H-4,7-methano-inden-1-ones followed by microwave-mediated Lewis acid-catalysed retro Diels-Alder reaction. An alternative route involving a modified Baylis-Hillman protocol followed by conjugate addition with alkylcuprates and a retro Diels-Alder reaction was also investigated.     

固体酸催化合成马来酸二丁酯

制备了固体酸催化剂Zr(SO4)2/SiO2,并用于合成马来酸二丁酯,考察了Zr(SO4)2负载量、焙烧温度、焙烧时间等催化剂制备条件对催化活性的影响。采用FTIR、XRD、TG等方法对催化剂进行了表征分析。通过正交实验设计优化了固体酸Zr(SO4)2/SiO2催化合成马来酸二丁酯的工艺条件。实验结果表明,Zr(SO4)2/SiO2是合成马来酸二丁酯的良好催化剂,适宜的催化剂制备条件为:硫酸锆负载量57%,焙烧温度400℃,焙烧时间2 h。适宜的催化合成反应条件为:酐醇物质的量比为1∶2.5,催化剂用量为马来酸酐质量的6%,带水剂甲苯8 mL,反应时间2.0 h。在此条件下马来酸二丁酯的酯化率为98.5%。     

Vibrational spectra of halomethylidynetricobalt nonacarbonyl complexes

Infrared and Raman spectra (1400-100 cm⁻¹) are reported for the metal cluster complexes (μ₃ - YC)CO₃(CO)₉; YF, Cl and Br, and vibrational assignments for the YCCo₃ groupings proposed. Approximate force fields have been calculated for these groups and the results are compared with those derived in earlier work on related systems. The unusually high frequencies attributed to carbon-halogen stretching modes in these complexes are shown to result from appreciable coupling of these modes with the symmetric CoC stretching mode.     

三氯化铁催化合成三芳基甲烷化合物的研究

三甲基芳烷类化合物在染料、生物、医药领域具有的重要应用价值。本文研究了2,4,6-三甲基苯甲醛和N,N-二甲基间溴苯胺通过缩合反应制备三芳基甲烷化合物,考察了催化剂种类、反应溶剂、反应温度和反应时间对产物收率的影响。确定合成条件为以无水Fe Cl3作为催化剂、对二甲苯为溶剂、反应温度为128℃,反应时间为32h,目标产物收率达到80%左右,产物结构经质谱和氢核磁共振谱表征确认。     

Synthesis of quinoxaline derivatives catalyzed by PEG-400

<正>Polyethylene glycol(PEG) was found to be an effective catalyst for the condensation of 1,2-diamines with 1,2-dicarbonyl compounds to afford the corresponding quinoxaline derivatives in excellent yields under mild reaction conditions.     

硫酸氢钠催化合成异丁酸异丁酯

采用硫酸氢钠为催化剂催化异丁酸与异丁醇的酯化反应,合成了异丁酸异丁酯;考察了催化剂用量、n(异丁醇)∶n(异丁酸)、反应时间、带水剂种类和用量,以及硫酸氢钠重复利用等因素对酯收率的影响.结果表明,硫酸氢钠催化活性高,易分离回收,后处理方便,废液排放量少.适宜的反应条件为n(异丁醇)∶n(异丁酸)=2.5∶1(0.2mol异丁酸),硫酸氢钠1.5g,反应时间40min,环己烷5mL;相应的酯收率为91.9%.     

硫酸氢钠催化合成丁酸异戊酯

丁酸异戊酯有类似梨的水果香气 ,广泛应用于溶剂、日用香精和食用香精中[1,2 ] .目前 ,工业上主要采用硫酸催化丁酸和异戊醇酯化法来合成[3] ,为克服硫酸催化法的缺点 ,改善合成环境 ,人们曾研究过采用结晶氯化铁、超强酸及杂多酸等催化合成丁酸异戊酯[4～ 6] ,然而结晶氯化铁很易吸潮、难于保管和准确使用 ,超强酸和杂多酸需要制备 ,成本较高 .本文选用的硫酸氢钠 (ＮａＨＳＯ4 ·Ｈ2 Ｏ)是一种价廉易得的无机酸性晶体 ,易保管且使用方便 ,催化效果好 ,同时它又不溶于有机反应体系 ,具有一定的重复使用性能 ,至今未见用ＮａＨＳＯ4 ·Ｈ2 …     

脂肪酶Lipozyme 435催化合成海藻糖脂肪酸单酯

本文通过对溶剂系统的优化,以脂肪酶Lipozyme 435为催化剂,叔了醇/吡啶为溶剂,由海藻糖与脂肪酸的酯化反应可高选择性地合成海藻糖单脂肪酸酯.海藻糖单脂肪酸酯的溶解性能和临界胶束浓度(CMC)均随着脂肪链长度的增加而降低.预期具有合适的溶解性和CMC具有可作为安全、高效的新型增溶剂.     

Conjugate additions of carbon nucleophiles to cyclopentadienones

[reaction: see text] Reactions of cyclopentadienones 1 with alkylmagnesium bromides were investigated and gave 1,4 adduct and/or 1,2 adduct.     

Diastereoselectivity in an electrocyclization reaction of cyclopentadienones

Two cyclopentadienones were generated and both underwent conrotatory electrocyclization as expected based on Woodward-Hoffmann rules. This result lends support to the idea that these ring-closing reactions are, in fact, pericyclic processes.     

Synthesis of dinucleotides catalyzed by the guanyl-RN-ase of actinomycetes

Chemistry of Natural Compounds -