Bifunctional Schiff base/Ti(IV) catalysts for enantioselective cyanoformylation of aldehydes with ethyl cyanoformate

A new bifunctional titanium/Schiff base catalyst was developed for the enantioselective cyanoformylation of aldehydes with ethyl cyanoformate. The reaction proceeded smoothly with a mild reaction condition to afford the cyanohydrin ethyl carbonates in high yields (up to 96%) and good enantioselectivities (up to 85% enantiomeric excess). Copyright © 2013 John Wiley & Sons, Ltd.     

Room temperature MgI2-catalyzed Friedel–Crafts reaction between electron-rich (het)arenes and ethyl glyoxylate

Magnesium iodide-catalyzed addition of electron-rich (het)arenes to ethyl glyoxylate proceeds at room temperature with high chemoselectivity to afford ethyl 2-(het)aryl- 2-hydroxyacetates in yields up to 95%.     

Direct aldol condensation reaction of ethyl diazoacetate with trifluoromethyl ketones

An efficient and direct aldol-type condensation of ethyl diazoacetate with trifluoromethyl ketones was developed in the presence of dialkyl zinc. A series of trifluoromethylated products were obtained in good to excellent yields (60-95%). A preliminary extension to a catalytic enantioselective aldol reaction of ethyl diazoacetate to trifluoromethyl ketones (up to 72% ee) is also described.     

Proline-catalyzed direct asymmetric aldol reaction of trifluoroacetaldehyde ethyl hemiacetal with ketones

l-Proline-catalyzed direct asymmetric aldol reaction of trifluoroacetaldehyde ethyl hemiacetal with unmodified ketones smoothly occurred at ambient temperature to produce β-hydroxy-β-trifluoromethylated ketones with good to excellent diastereo (up to 96% de) and enantioselectivities (up to 91% ee).     

磷钨酸-拟薄水铝石负载催化剂合成对羟基苯甲酸乙酯

以拟薄水铝石固载的磷钨酸为催化剂,通过对羟基苯甲酸乙酯的合成产率及磷钨酸的溶脱率的测定,考察催化剂的催化性能和固载程度。结果表明,对羟基苯甲酸乙酯的合成最高产率达到83.8%,溶脱率为2.8%。重复使用6次后,总的溶脱率为12.5%。由此可见,该催化剂是一种固载程度良好的环境友好型催化剂。     

由乳酸铵直接合成乳酸乙酯的研究

乳酸乙酯在传统的消费领域中多用于香精、香料、食品及酿酒行业,是良好的添加剂;此外在制药工业中用做压制药片的润滑剂,药物心得静的中间体;饲料工业中用做香味剂。乳酸乙酯最具发展前景的用途是：利用其具有无毒、溶解性好、不易挥发等特点作为“绿色溶剂”,它可以取代目前使用的许多对人和环境有毒的溶剂,如：卤代类、醚类以及破坏臭氧层的氟氯碳溶剂等,同时乳酸乙酯又具有可生物降解性,因此乳酸乙酯是极具开发价值和应用前景的“绿色产品”。     

Synthesis of polyfunctionalized 1,2,3,4-tetrahydropyridines from ethyl acetoacetate and cyclic aminals

Polyfunctionalized 1,2,3,4-tetrahydropyridines were synthesized in up to 90% yield by condensation of ethyl acetoacetate with cyclic aminals in methanol.     

Enantioselective organocatalytic synthesis of quaternary α-amino acids bearing a CF3 moiety

A highly enantioselective Friedel-Crafts reaction catalyzed by a chiral phosphoric acid was developed. N-Boc-protected ethyl trifluoropyruvate imine was activated by 6 mol % of catalyst and reacted with a wide variety of indole derivatives to afford quaternary α-amino acids in excellent yields (up to 99%) and high enantioselectivities (up to 98:2 er).     

除草剂中间体R-(+)-2-(4-羟基苯氧基)丙酸酯的不对称合成

报道了一种合成苯氧丙酸类除草剂重要中间体R－（＋）－2－（4－羟基苯氧基）丙酸乙酯（即R－（＋）－HPE）的方法，以L－乳酸为起始原料，先经酯化合成L－乳酸乙酯，再与对甲苯磺酰氯反应制备L－对甲苯磺酰乳酸乙酯，再与对苯二酚综合获得R－（＋）－2－HPE，产品的总收率为72.1%。通过元素分析和红外光谱测定，确定了所合成的R－（＋）－HPE的化学结构和纯度；由旋光度的测定，确定了所合成的R－（＋）－HPE的光学纯度为95.7%。     

在铌酸催化剂上气相酯化反应的研究

氧化铌在含水体系中表现出强酸性,因而得到越来越多的应用。有机羧酸酯是一类重要的化工产品,一般用硫酸等作催化剂,但存在腐蚀设备等问题。我们采用铌酸催化剂进行乙醇和6种羧酸的常压气相酯化反应。实验表明,不仅乙醇转化性高,而且酯的选择率高达100％,同时,也克服了上述液体酸催化剂的缺点,有希望成为酯化反应的有效催化剂。     

Reactions of Elemental Phosphorus and Phosphine with Electrophiles in Superbasic Systems: XIV.1 Phosphorylation of 2-Vinylnaphthalene with Elemental Phosphorus and Phosphines in the KOH-DMSO System

Elemental phosphorus (red or white) reacts with 2-vinylnaphthalene while heating at 90-96°C in the superbasic KOH-DMSO system to form 2-(2-naphthyl)ethylphosphine, 2-(2-naphthyl)ethylphosphinic acid, bis[2-(2-naphthyl)ethyl]phosphine, bis[2-(2-naphthyl)ethyl]phosphine oxide, and tris[2-(2-naphthyl)ethyl]phosphine oxide in a total yield of up to 40%. Selective conditions for preparing the tertiary phosphine oxide from white phosphorus and 2-vinylnaphthalene in 58% yield were found. Phosphine and (2-phenylpropyl)phosphine add to 2-vinylnaphthalene in the KOH-DMSO system to form, under certain conditions, corresponding secondary phosphines in high yields.     

[3+2] Dipolar cycloadditions of an unstabilised azomethine ylide under continuous flow conditions

The [3+2] dipolar cycloaddition reactions of the unstabilised azomethine ylide precursor benzyl(methoxymethyl)(trimethylsilylmethyl)amine with 12 electron-deficient alkenes in the presence of catalytic trifluoroacetic acid are examined under continuous flow conditions (20-100 °C, 10-60 min residence time). The more reactive and hazardous alkenes such as ethyl acrylate, N-methylmaleimide and (E)-2-nitrostyrene afford substituted N-benzylpyrrolidine products in 77-83% yields, whereas less reactive dipolarophiles such as (E)-crotononitrile and ethyl methacrylate give lower yields (59-63%). Under optimised conditions, the reaction with ethyl acrylate is scaled up to afford ethyl N-benzylpyrrolidine-3-carboxylate (30 g, 87%) in 1 h.     

Synthesis of new chiral hydroxy oxazolines and their use in the catalytic asymmetric phenyl transfer to aldehydes

Starting either from benzoylformic acid or ethyl oxamate and enantiopure β-amino alcohols, several chiral α-hydroxy oxazolines have been prepared by short synthetic routes. Subsequently, they have been employed in the catalytic asymmetric phenyl transfer to various aldehydes, using a mixture of triphenylborane and diethylzinc as the phenyl source. The corresponding secondary alcohols were obtained with good enantioselectivities (up to 81% ee) and up to 92% yield.     

Chemoselective synthesis of 6-amino(alkoxy)-1,4,5,6-tetrahydropyridines from cyclic β-alkoxyvinyl α-ketoester

The synthetic versatility of ethyl 2-(2-ethoxy-3,4-dihydro-2H-pyran-5-yl)-2-oxoacetate for the synthesis of ethyl 2-oxo-2-(1-alkyl/aryl-6-(amino/ethoxy)-1,4,5,6-tetrahydropyridin-3-yl)acetates, from the reaction with primary amines, is presented. The methodology proposed herein is highly chemoselective, and twenty products were obtained in moderate to good yields (up to 87%).     

Unexpected Reactivity of Ethyl 2-(Diethylphosphono)Propionate Toward 2,2-Disubstituted-1,3-cyclopentanediones

Abstract

A Horner-Wadsworth-Emmons reagent-ethyl 2-(diethylphosphono)propionate in the reaction with 2,2-disubstituted-1,3-cyclopentanediones, results in 4-oxohexanoic acid ethyl ester derivative up to 90% isolated yield. ³¹P-¹³C- and ¹H-NMR study of the intermediates of the reaction involving the ethyl 2-(diethylphosphono)propionate was accomplished.     

固相萃取-气相色谱法测定茶叶中甲胺磷残留量

茶叶样品经乙酸乙酯提取,上清液于50℃蒸发至近干,加入乙酸乙酯溶解残渣后,经硅胶-石墨化碳混合柱净化。先以乙酸乙酯洗脱去除杂质,再以碱化乙腈洗脱并收集流出液,在50℃蒸发至近干,加乙酸乙酯定容至1mL,供气相色谱分析。采用DB-1701色谱柱分离和火焰光度检测器检测,所得甲胺磷的线性范围为0.010～1.00mg·L-1,方法的检出限(3S/N)为0.005mg·kg-1。在0.010,0.020,0.080 mg·kg-1 3个浓度水平下进行回收试验,甲胺磷的回收率在85.0%～90.9%之间,相对标准偏差(n=6)在2.2%～4.3%之间。     

Reaction of divinyl selenide with secondary phosphine chalcogenides

Under the conditions of free-radical initiation (AIBN, UV irradiation), divinyl selenide regioselectively reacts with secondary phosphine sulfides and phosphine selenides to afford, depending on the ratio of the reagents, mono- or diadducts mainly of the anti-Markownikoff structure. The conditions which allow obtaining the diadducts in up to 97% yield are found. By the example of 2-{[2-(diphenethylphosphoroselenoyl) ethyl]selanyl}ethyl(diphenethyl)phosphine selenide the diadducts were shown to react with aqueous hydrogen peroxide at 53–56°C to give vinyl(diphenethyl)phosphine oxide in 76% yield.     

Asymmetric synthesis of 2,3-dihydro-4-pyranones by reaction of chiral 3-alkoxycyclobutanone and aldehydes

Chiral cyclobutanone which had ethyl l-lactate as a chiral auxiliary at the 3-position reacted with aldehydes to give 2,3-dihydro-4-pyranones in up to 93% ee by combined use of titanium(IV) chloride and tin(II) chloride.     

金鸡纳生物碱-9-O-三甲基硅衍生物催化的不对称“中断的”Feist-Bénary反应

将6种金鸡纳生物碱-9-O-三甲基硅(TMS)衍生物用于催化环己二酮与溴乙酰甲酸乙酯/β-取代的溴乙酰甲酸乙酯的不对称“中断的”Feist-Bénary反应,得到了高的化学产率(85％～97％)和最高达90％ee的立体选择性。     

Improvement of the Asymmetric Induction from Lactic Acid Derivatives Enhanced by ZnCl2

Lactic acid methyl ester, lactic acid ethyl ester, and (2S)‐ethyl‐2‐methoxy propanate were used as solvents for acetophenone reduction by boron hydrides. Moderate enantiomeric excess up to 60% was obtained in the presence of stoichiometric amounts of ZnCl₂. There is evidence for an intermediate between the solvents, the Lewis acid and the ketone, as the prerequisite for chirality transfer. The importance of the Lewis acid is to strengthen interaction between solvent and educt compared to the hydroxy group.