Reduction of Aromatic Aldehydes,Ketones with Acyloxy Substituent at the Ortho-position by NaBH4 in the Presence of Waters

n unusual reduction of some aromatic aldehydes, ketones by sodium borohydride was discovered. In a THF/H₂O or DMSO/H₂O solvent system the aromatic aldehydes, ketones with acyloxy substituent on the ortho-position to the carbonyl group can be reduced to the corresponding alkyl phenols. This unusual reduction is applicable also to the corresponding alcohols of all the above aldehydes, ketones. A putative mechanism was suggested. In addition to the above aldehydes, ketones, benzyl alcohols, certain 4-acyloxybenzyl esters(probably also the 2-substituted analogues) such as 4-benzoyloxybenzyl benzoate was also found to be reduced to methylphenol by this unusual reduction.     

An efficient reduction of N-substituted carbonylimidazolides into formamides by NaBH4

A novel, simple and versatile protocol was investigated for highly efficient synthesis of formamides through reducing N-substituted carbonylimidazolides by NaBH₄ under mild reaction conditions. By this method, not only carboxylic acids or isocyanates, but also amines can readily access formamides with high yields.     

环糊精介入酵母细胞催化芳香酮的不对称还原反应

以苯乙酮、苯丙酮、4'-甲基苯乙酮和4'-氯苯乙酮为底物,研究了酵母细胞催化芳香酮的不对称还原反应,分别考察了添加剂β-环糊精和羟丙基-β-环糊精对酵母细胞催化芳香酮的不对称还原反应的影响,结果表明芳环上取代基的空间效应和电子效应对转化率和对映体过量值有显著的影响.环糊精是通过提高酵母液的催化效率和对底物形成包结来影响反应结果的,其中底物芳环对位有无取代基是添加剂影响反应结果的关键因素.环糊精加入量根据底物的不同在3~20mmol/L之间较合适.     

CuFe_2O_4纳米粒子催化芳香酮的不对称硅氢化反应

分别采用共沉淀法、溶胶-凝胶法和溶剂热法制备得到CuFe_2O_4纳米粒子,以(R)-联萘二苯基膦[(R)-BINAP]为手性配体、聚甲基氢硅氧烷(PMHS)为硅氢化试剂,将制得的CuFe_2O_4纳米粒子用于催化芳香酮的不对称硅氢化反应.结果表明,溶剂热法能制得分散性好、粒径小且分布均匀的CuFe_2O_4纳米球,其催化活性明显优于其它2种方法.在添加剂t-Bu OK和t-BuOH的共同作用下,CuFe_2O_4纳米粒子的催化活性得以明显改善,最终得到一种高效的非均相催化体系CuFe_2O_4/t-Bu OK/t-BuOH.在室温和空气氛围下,用于催化芳香酮的不对称硅氢化反应,底物转化率和产物对映体过量值分别高达99%和92%.研究证实底物芳环上取代基的电子效应和空间位阻明显影响不对称硅氢化反应的结果.CuFe_2O_4纳米催化剂在外加磁场的作用下能较易从反应体系中分离回收,且催化剂经4次循环利用后仍具有较高的催化活性.     

Enantioselective Reduction of Prochiral Ketones with NaBH4/Me2SO4/(S)-Me-CBS

The enantioselective reduction of prochiral ketones with NaBH₄/Me₂SO₄/(S)-Me-CBS is described. Borane is generated in situ via the reaction of NaBH₄ with Me₂SO₄ in tetrahydrofuran, which is as efficient as the commercial one. Such in situ–generated borane reagent was applied to reduce prochiral ketones in the presence of chiral oxazaborolidine catalyst directly. The corresponding chiral secondary alcohols were obtained with excellent enantiomeric excesses (93–99% ee) and good to excellent yield (80–99%).     

Pyridinium Iodochloride: An Efficient Reagent for Iodination of Hydroxylated Aromatic Ketones and Aldehydes

Direct iodination of several reactive aromatic compounds like hydroxy substituted acetophenones and aldehydes with pyridinium iodochloride (PyICl) proceeded smoothly to afford the corresponding aromatic iodides in good to excellent yield. Pyridinium iodochloride has been found to be an efficient solid iodinating reagent with no hazardous effect and it can be handled safely.     

Ambient Ionic Liquids Used in the Reduction of Aldehydes and Ketones

The sodium borohydride reduction of aldehydes and ketones to corresponding alcohols has been accomplished via the use of ionic liquids. The alcohols are easily obtained with excellent yields and the ionic liquid BMImBF4 could be reused.     

对-甲苯乙酮与芳香醛和芳香胺的Mannich反应

Mannich反应是合成新化合物的重要方法 [1] ,其对应的产物 Mannich碱常常具有广泛的生物活性 [2 ] .文献报道 ,对 -甲苯乙酮的 Mannich碱具有抑癌 [3]和麻醉拮抗 [4 ]等生物活性 ,但是文献中对 -甲苯乙酮 Mannich碱的合成却是从胺交换法 [5] 、酮交换法 [6] 、查耳酮与胺的 Michael加成[7] 、Schiff碱与酮的缩合 [8～ 14 ] 、β-内酰胺与有机锂的亲核裂解 [15] 等间接方法得到的 .即使是从直接法合成 ,一般也是甲醛参与的 Mannich反应 .虽然芳香醛和芳香胺同时参与的 Mannich反应已有报道 [16] ,但对 -甲苯乙酮与芳香醛和芳香胺直接进行…     

One Pot Reduction of Imines Generated in-situ from Aldehydes and Amines by the NaBH4-InCl3 System

A combination of sodium borohydride and a catalytic amount of indium（Ⅲ） chloride in acetonitrile reduces imines formed in-situ from aldehydes and amines to the corresponding functionalised secondary and tertiary amines in moderate to good yields. Noteworthy is that highly chemoselective reactions were achieved in the presence of other functional groups such as halogens, carbon-carbon double bonds and hydroxyl groups.     

NaBH4/DOWEX(R)50WX4: A Convenient Reducing System for Fast and Efficient Reduction of Carbonyl Compounds to Their Corresponding Alcohols

The reduction of a variety of carbonyl compounds was efficiently carried out with NaBH₄/DOWEX(R)50WX4 system. The reactions were performed to give the corresponding alcohols derivatives in perfect yields in THF at room temperature. Reduction of acyloins and a‐diketones by this reducing system produced efficiently the corresponding vicinal diols. Also, the reduction of aldehydes over ketones has been accomplished successfully by this system. Regioselectivity of this system was also investigated with exclusive 1,2‐reduction of conjugated carbonyl compounds to their corresponding allylic alcohols in high to excellent yields.     

Mechanochemical Reaction of Aromatic Ketones and Aldehydes in the Presence of Zn-ZnCl2

The solvent-free reactions of aromatic ketones and aldehydes in the presence of Zn-ZnCl2 were performed with the aid of high-speed vibration mill, Retsch MM200 mixer mill and Retsch RM100 mortar grinder to give pinacol coupling and reduction products in varying yields.     

金鸡纳碱衍生物修饰的负载铱催化剂催化芳香酮不对称加氢

以金鸡纳碱衍生物作为手性修饰剂, 研究了三苯基膦稳定的Ir/SiO₂催化剂催化芳香酮多相不对称加氢. 通过电感耦合等离子体原子发射发谱(ICP-AES)、高分辨透射电镜(HRTEM)、X 射线光电子能谱(XPS)、Brunauer-Emmett-Teller (BET)比表面积测试等固体表面分析手段对负载铱催化体系进行了表征; 利用红外(IR)光谱、固体核磁共振(NMR)等分析手段初步表征了负载铱多相催化体系中手性修饰剂-金属-稳定剂在载体上的相互作用; 利用“均相与多相催化体系的对比”、“催化剂稳定性实验”、“汞中毒实验”等方法阐明了手性修饰的负载铱催化体系是多相催化体系. 还考察了稳定剂种类、修饰剂种类、金属负载量、溶剂、碱添加剂种类等因素对不对称加氢反应的影响. 结果表明, 金鸡纳碱衍生物对Ir/SiO₂催化剂具有较好的修饰作用, 在优化反应条件下苯乙酮及其衍生物加氢反应的对映选择性为52%-96%, 4-乙酰基吡啶、2-乙酰基噻吩及2-乙酰基呋喃加氢反应的对映选择性可分别达到74%、75%及63%.     

芳香醛缩肼基甲酸甲酯酰腙化合物的合成

以碳酸二甲酯和水合肼为原料合成了肼基甲酸甲酯,与一系列芳香醛在70℃反应30min得到芳香酰腙化合物,产率为76%～95%,产物由核磁共振谱,红外光谱及质谱表征予以确认。本文所报道方法具有反应条件温和、产量高、产物易纯化的特点。     

Efficient Synthesis of Dicycloalkenopyridines： One-pot Multicomponent Condensation of Aldehydes with Cyclic Ketones

Under microwave irradiation, the one-pot multicomponent condensation reaction of three moles of aromatic aldehydes with two moles of cyclic ketones having free α,α'-methylene positions such as cyclopentanone or cyclohexanone in the presence of ammonium acetate and acetic acid afforded dicycloalkenopyridines with two α-arylidene groups in high yields. Under the similar reaction condition, the reaction of aromatic aldehydes with 1-tetralone having only one α-methylene position alternatively resulted in 10-ary...     

低价钛诱导的芳香邻二酮及α-羟基酮的还原偶联反应

Treatment of aromatic 1 , 2-diketones or aromatic a-hydroxy ketones with an activated low-valent titanium reagent, prepared by reduction of TiCl3·1/3AlCl3 with a Zn-Cu reagent, gave an intermolecular coupling reaction leading to the (Z)-1, 2.3.4-tetraaryl-2-butenes. Apossible coupling reaction process was proposed for the aromatic a-hydroxy ketones.     

Reduction of aromatic and aliphatic keto esters using sodium borohydride/MeOH at room temperature: a thorough investigation

Reduction of keto esters is a valuable alternative to produce diols. Sodium borohydride/MeOH system at room temperature and short reaction time efficiently reduced α, β, γ, and δ-keto esters having α-keto esters as the most reactive. The ester functionality was reduced effectively due to the presence of oxo group that somehow facilitates the formation of ring intermediate. As expected, the chemoselective experiments showed that ester functionality was not reduced using this system. This study presents a simple, easy, and benign reduction process of various keto esters to its corresponding diols.     

Selective Aldehyde Reduction in Ketoaldehydes with NaBH4-Na2CO3-H2O at Room Temperatures

A variety of aliphatic and aromatic ketoaldehydes were reduced to the corresponding ketoalcohols with a mixture of sodium borohydride (1.2 equivalents) and sodium carbonate (sixfold molar excess) in water. Reactions were performed at room temperatures over (typically) 2 h, and yields of isolated products generally ranged from 70% to 85%. A bis-carbonate-borane complex, [(BH₃)₂CO₂]^2? 2Na⁺, possibly formed from the reagent mixture, is likely the active reductant. The moderated reactivity of this acylborane species would explain the chemoselectivity observed in the reactions. The readily available reagents and the mild aqueous conditions make for ease of operation and environmental compatibility, and make a useful addition to available methodology.     

Novel Chemoselective Reduction of Aldehydes in the Presence of Other Carbonyl Moieties with Thiourea Dioxide

Reduction of a variety of aldehydes in the presence of other carbonyl moieties to the corresponding alcohols occurs chemoselectively in high yields upon treatment with inexpensive reagent thiourea dioxide (TUDO) in aqueous alkali–ethanolic system for 2 h at 90 °C.     

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。