Practical and Chemoselective Reduction of Acyl Chloride to Alcohol by Borohydride in Aqueous Dichloromethane

A simple methodology for the reduction of acid chlorides to their corresponding alcohols has been developed. Various carboxylic acids were converted to alcohols in excellent yields using NaBH₄-K₂CO₃ in a mixed solvent system of dichloromethane and water (1:1) in the presence of a phase-transfer catalyst at low temperature. The importance of the work is its simplicity, selectivity, excellent yield, and very short reaction time. This new reduction condition has proved to be an excellent chemoselective method for a range of acid chlorides in the presence of various functional groups.     

硼氢化钠还原樟脑制备异冰片——国外本科生实验的介绍与讨论

冰片作为一种自然界广泛存在的次级代谢产物,可以通过樟脑的还原反应制备。但由于冰片极易氧化为樟脑,实验室中常使用硼氢化钠还原樟脑制备冰片的方法。该法可能生成2种冰片异构体,可以通过动力学控制获得其中一个异冰片从而使其成为不可逆反应。该有机化学实验设计在美国与欧洲国家均有涉及,但在国内教材中只是单纯设计为环己酮等单分子的还原反应,缺乏体现化学在解决实际问题中的实用性以及课堂的趣味性。该实验的引进不失为改进国内有机化学实验设计的良好素材。     

硼氢化钠还原潜手性酮反应机理的量子化学研究

用从头计算方法对硼氢化钠不对称还原对甲基环己酮的机理进行了研究. 探讨了四元环和六元环机理, 其中每种机理有三种途径, 主要的途径是经过过渡态的两步反应途径. 计算结果表明, 无溶剂参与反应的四元环过渡态机理虽然能解释其还原历程, 但计算所得的对映体组成与文献值相差很大. 而对质子性溶剂异丙醇参与的六元环机理的研究发现反应产物的对映体组成的计算结果与文献实验值吻合较好. 这表明该反应主要经历六元环过渡态的两步反应历程.     

bio(oh)-nabh4还原法制备氧化偶氮苯类化合物

以NaOH溶液快速沉淀BiCI3溶液制备了BiO(OH),研究了BiO(OH)对NaBH4还原芳香族硝基化合物的催化性能,考察了NaBH4用量对反应的影响.结果表明,在温和条件下BiO(OH)具有很高的催化活性和选择性.NaBH4和芳香族硝基化合物的摩尔比为1.04:1,在甲醇中室温反应2 h,芳香族硝基化合物主要被还原为氧化偶氮苯类化合物,收率80.4%～96.9%.该催化剂重复使用5次后活性没有明显下降.于120℃再生后,其活性与新制备催化剂相当.     

NaBH_4还原二氟乙酸乙酯合成二氟乙醇的研究

采用硼氢化钠(NaBH4)还原二氟乙酸乙酯(CF2HCOOCH2CH3)合成二氟乙醇(HCF2CH2OH)。探讨NaBH4用量、溶剂、反应温度和反应时间等因素对反应的影响。实验结果表明:在投料比n(NaBH4)/n(CF2HCOOCH2CH3)=0.6,乙醇为溶剂,温度0℃反应条件下,二氟乙醇的收率可以达到98.1%。在极性溶剂中,随着反应温度的升高(5℃及以上),NaBH4的分解加剧,低温对反应有利。     

微波干法催化醛酮与胺的缩合反应

利用微波辐射和固体中性Al2 O3 载体催化醛酮与胺的缩合反应的方法合成了十六种亚胺 ,研究了微波功率、作用时间、产物提取方式等因素对反应的影响 ;与无微波作用的一般合成方法相比 ,该法明显地提高反应速度及产率 ;文中用低极性熔点递变物质灌装毛细管的方法观测微波作用下反应温度 ,探讨微波作用化学反应的机理 ,其机理除与微波加热作用有关外还与分子间氢键及分子的缔合性有关。     

The Solubility of Sodium Sulfate and the Reduction of Aqueous Sulfate by Magnetite under Near-Critical Conditions

The solubility of Na₂SO₄ (s) (thenardite) and the interactions between magnetiteand aqueous Na₂SO₄ near the critical point of water have been determined in azirconium-alloy flow reactor at temperatures 350°C t 375°C and isobaricpressures 190 p 305 bar. The experimental solubility data are describedwell as a function of temperature and solvent density ₁ byln x(Na₂SO₄, aq.) = –10.47 – 27550/T +(4805/T) ln ₁.The interaction between magnetite and Na₂SO₄ (aq.) was examined from 250 to370°C at molalities near the saturation composition of Na₂SO₄ (s). While no solidreaction products were observed, HS^– (aq.) was observed to form above 350°Cby sulfate reduction, as a product of the reaction8 Fe₃O₄(s) + Na₂SO₄ (aq.) + H₂O(l)= 12 Fe₂O₃ (s) + NaHS (aq.) + NaOH (aq.).The reduction reaction appears to be controlled by surface reaction kinetics, ata level well below the equilibrium molality of HS^– (aq.). Metallic iron reactedwith Na₂SO₄ (aq.) in a similar fashion at temperatures above 350°C, to yieldhigher molalities of HS^– (aq.).     

Rapid Synthesis of Alkyloxy Porphyrins Under Microwave Irradiation

Alkyloxy porphyrins have been prepared by direct coupling of 5-para-hydroxyphenyl-10,15,20-triphenylporphyrin and alkyl halides under microwave irradiation within several minutes. The length of the alkyl halides has no obvious effect on the yields and reaction time; however, the steric structure of the alkyl halides has a great impact on the reaction time. All the products were confirmed by ¹H NMR.     

聚合物硼氢阴离子还原剂的制备及其对酯的还原研究

氯型季我安盐型强碱性阴离子交换树脂７１１＾＃与硼氢化钾反应制得聚合物硼氢阴离子还原剂，树脂容量３．２ｍｍｏｌ ＢＨ４／ｇ。用于不同酯化合物的还原，操作简便，树脂可再生重复使用。     

Oxidative Cleavage of Epoxides Using Aqueous Sodium Paraperiodate

A simple and mild method in water for direct conversion of epoxides to corresponding aldehydes has been developed using sodium paraperiodate (Na₃H₂IO₆). High yields of corresponding aldehydes were obtained.     

硼氢化钠还原-无色散原子荧光法测定茶叶中汞

建立了汞的硼氢化钠还原－无色散原子荧光测定方法,在最佳条件下,荧光强度与汞浓度在0－25μg/L范围内呈线性关系,相关系数0．9991,检出限0．02μg/L。用拟定的方法测定了茶叶中的汞,回收率为91．6％－98．3％,变异系数不超过5．2％。     

Direct Estirification and Amidation of Phosphinic Acids Under Microwave Conditions

Abstract

Phosphinic acids may be efficiently esterified in microwave-assisted reactions with alcohols. Especially alcohols with longer alkyl chain are suitable reagents for direct esterifications. At the same time, the direct amidation cannot be complete under such conditions. Hence, the tradional amidations via the phosphinic chloride intermediates have to be applied. The values of activation enthalpies and reaction enthalpies obtained by quantum chemical calculations justified the experimental observations. Microwave has a potential in overcoming relatively high activation enthalpies.     

Al(OTf)3 as an Efficient Catalyst for One-Pot Synthesis of Primary Diethyl 1-Aminophosphonates Under Solvent-Free Conditions

A simple and general method has been developed for the one-pot, three-component synthesis of a variety of primary 1-aminophosphonates catalyzed by Al(OTf)₃ under solvent-free conditions in good to high yields.     

复合还原剂硼氢化钠/三氯化铁对亚砜的还原

硼氢化钠是一种温和、高选择性的亲核还原剂。一般它只能还原醛、酮和酰氯,而对其它功能团不起作用。因而其应用范围有一定的限制。据文献报道,某些金属卤化物能有效地提高硼氢化钠的还原性能^[1]。复合还原剂硼氢化钠/三氯化铁已应用于将β-二烷基氨基共轭烯酮还原为相应的饱和γ-氨基醇^[2]。本文研究了硼氢化钠/三氯化铁对亚砜的还原反应。     

Synthesis of Ferrocenyl Schiff Bases Under Solvent-Free Conditions Using Microwave Irradiation

Ferrocenyl imines 3a–f were synthesized using solvent-free methods by mixing ferrocene carbaldehyde 1 with amines 2a–f under microwave irradiation. The imines were obtained in good yield in short reaction times.     

Aqueous Wittig Reactions of Aldehydes with In Situ Formed Semistabilized Phosphorus Ylides

The Wittig reactions of three semistabilized phosphorus ylides generated in situ from the corresponding phosphonium salts with aldehydes in water without any organic cosolvent were investigated. Most of the olefination reactions completed within between 5 min and 4.5 h in refluxing water containing 1.5 equiv of LiOH and 1.4 M LiCl to afford the products in 65–100% yields. The E∶Z selectivity depended not only on the substituent attached to the benzene ring of the ylides but also on the substituent bound to the aromatic aldehydes. LiCl promotes the aqueous Wittig reactions and suppresses decomposition of the ylide or the corresponding phosphonium salt.     

A Rapid and Efficient Multicomponent Synthesis of Bi-Quinolines Under Solvent-Free Conditions

An efficient synthesis of substituted condensed quinolino-quinolines has been achieved in a one-pot reaction from 2-hydroxy/mercapto/seleno-4-methylquinoline and 2-mercapto/seleno-3-formyl quinolines using anhydrous ammonium hydroxide as the reductant by microwave irradiation under solvent-free conditions.     

硼氢化钠催化水解制氢*

硼氢化钠（NaBH₄）催化水解制氢是一项具备车载氢源应用前景的储氢/制氢一体化技术。本文介绍了该技术催化水解制氢的原理,综述了制氢催化剂、反应动力学、反应机理、反应装置的设计和反应副产物回收利用的最新研究进展,讨论了该技术研发中需解决的问题。水解制氢系统的实际应用需研发高效、耐久性负载型催化剂。制氢装置的设计应考虑反应热的综合利用、燃料电池产生的水循环利用及膜分离技术的应用。NaBH4的高效再生将降低其生产成本,实现NaBH4基水解制氢系统的商业化应用。     

Convenient Synthesis of 2-Aminothiophene Derivatives by Acceleration of Gewald Reaction Under Ultrasonic Aqueous Conditions

Under ultrasound irradiation and in the presence of H₂O/Et₂NH, ethyl cyanoacetate or malononitrile can combine with α-methylene carbonyl compounds and elemental sulfur to efficiently yield 2-aminothiophene derivatives within a few minutes. Products are easily obtained by simple filtration because of their spontaneous precipitation in the reaction mixtures.