羧酸经苯并咪唑还原为醛的新合成方法研究

羧酸经苯并咪唑还原为醛的新合成方法研究史真顾焕（西北大学化学系西安７１００６９）醛是一类重要的有机化合物，无论是在有机化学的基础研究还是应用研究中，醛类化合物都占有特殊的重要地位。醇的氧化是制备醛的主要方法之一。以羧酸为原料，通过羧酸衍生物的还原得到...     

光学活性N,N-二烷基-β-氨基醇硼烷配合物对酮的不对称还原反应

从天然氨基酸出发制得的九种新的光学活性N,N-二烷基-β-氨基醇,分别与硼烷反应生成相应的手性恶唑硼烷配合物并将其用于不对称还原反应中. 硼烷-手性恶唑硼烷-还原体系能将脂肪酮和芳香酮还原为仲醇, 化学还原收率可达100%,光学收率也比较高.并简单讨论了立体效应, 反应温度和溶剂效应对此还原反应的影响.     

羧酸及其衍生物的NaBH4还原体系研究进展

NaBH4还原体系可以快速、高效、选择性地还原羧酸及其衍生物。本文介绍了8类NaBH4还原体系的最近研究成果。通过对各个还原体系的分析,讨论了各类还原体系的反应机理和反应条件,并比较了不同还原体系的还原能力和适用范围。     

固载硼氢还原剂在有机合成中的应用

综述了不同聚合物载体和无机载体担载的硼氢还原剂的制备及其在有机合成中的应用。     

BER催化还原一些含氮功能基化合物的研究

用强碱性阴离子交换树脂制备了硼氢阴离子交换树脂还原剂(BER),使其在氯化铜等金属化合物的催化下还原一些芳香硝基、氰基、氮氮双键等含氮功能基化合物.还研究了BER的制备条件:如温度、溶剂、不同金属化合物对还原反应的影响,并初步探讨其反应机理.     

不对称硼烷还原合成手性氨基醇

用原位生成的手性噁唑硼烷为催化剂,用2molBH3对1molα 或β 氨基酮进行了对映选择性还原,生成光学活性氨基醇 硼烷络合物,后者脱去BH3后给出光学活性氨基醇,ee值最高达99%.讨论了氨基酮结构与反应选择性的关系.     

新的聚合物支载硼氢负离子还原剂系统研究 3: 聚合物支载还原剂III

硼氢化钠的低分子还原系统研究很多,但其聚合物支载还原剂相对来说就很少,而且仅以强碱型阴离子交换树脂来制备的聚合物试剂。为了寻找用途更广泛的、新的聚合物支载还原剂,我们进行了硼氢负离子的聚合物还原系统的研究;发现能用弱酸型阳离子交换树脂制备出新的聚合物支载还原剂。前文报道了用NaBH_4的水溶液和阴离子交换树脂     

低价钛引起的羧酸衍生物与芳酮的还原偶联反应

本文报道了在低价钛试剂作用下羧酸衍生物与芳酮的还原偶联反应.     

9-BBN还原1,7-辛二烯-3-醇的研究

本文报道了用9-BBN与1,7-辛二烯-3-醇进行硼氢化反应的结果。这个反应的区域选择性极低,除生成1-辛烯-3-醇(47％)外,同时还生成了7-辛烯-3-醇(41％)和辛醇-3(12％)。     

硅磷酸铝分子筛催化羧酸的酯化反应研究

用新型硅磷酸铝分子筛和改性的硅磷酸铝分子筛催化脂肪族羧酸与脂肪族醇的酯化反应，以正戊酸分别与正丙醇、正丁醇、正戊醇和正辛醇以及正辛醇分别与乙酸、丙酸、正丁酸、正戊酸和正己酸的酯化反应作为探针实验进行了系统研究，实验结果显示，改性的硅磷酸铝分子筛比不改性的硅磷酸铝分子筛具有更高的酯化催化活性，实验发现，反应物的结构对酯化反应产生了显著的影响，文章揭示了新型硅磷酸铝分子筛和改性的硅磷酸铝分子筛对于羧酸的直接酯化反应的系列规律性。     

Triflylpyridinium Enables Rapid and Scalable Controlled Reduction of Carboxylic Acids to Aldehydes using Pinacolborane

Building up new and efficient methods for the controlled conversion of carboxylic acids to aldehydes is important. Herein, we report a rapid, modular and scalable method for the conversion of carboxylic acids to aldehydes using pinacolborane at ambient temperature, in which a triflylpyridinium reagent is used. The conversion of carboxylic acid to intermediate acylpyridinium by triflylpyridinium is new. A binary pyridine-coordinated boronium complex is generated after reduction. The unprecedented reduction of the acylpyridinium by HBpin opens up a practically direct synthesis of aldehydes from carboxylic acids. Theoretical studies indicate that the reduction of acylpyridinium requires a lower activation free energy than that of the product aldehyde. The synthetic advantage of this protocol is further highlighted by the scalable synthesis of aldehyde via continuous flow process. Configuration retention for chiral acids are presented in those syntheses.     

羧酸气体热容的测定与研究

The vapor heat capacities of acetic acid, propionic acid, n-butyric acid at various temperatures under atmospheric pressure were measured with a multicomponent vapor flow calorimeter. The results show that the vapor heat capacities of carboxylic acids are much larger than those of the ideal gases at the same temperature and that the vapor heat capacities decrease with increasing temperature. The effect of association in the vapor phase on the vapor heat capacity was studied.     

Reductive coupling reaction of aldehydes using indium(III) triflate as the catalyst

A reductive coupling reaction was effectively developed to convert an aldehyde to its symmetrical ether. The successful reactions required Et₃SiH and CH₂Cl₂ as the suitable solvent in the presence of a catalytic amount of In(OTf)₃. Various aldehydes were subjected to the method, and each afforded the expected ethers in good to excellent yields.     

Metal-free oxidative self-coupling of aldehydes or alcohols to symmetric carboxylic anhydrides

A metal-free synthesis of symmetrical anhydrides has been developed starting from aldehydes, both aliphatic and aromatic or primary benzylic alcohols. The reaction occurs at room temperature and makes use of trichloroisocyanuric acid (TCCA) as an oxidant providing the desired carboxylic anhydrides in satisfactory yields.     

Mild and Efficient Synthesis of Carboxylic Acid Anhydrides from Carboxylic Acids and Triazine Coupling Reagents

Abstract

Anhydrides of carboxylic acids were obtained in 53%–95% yield by treatment of appropriate carboxylic acids with 2‐chloro‐4,6‐dimethoxy‐1,3,5‐triazine (CDMT) or 2,4‐dichloro‐6‐methoxy‐1,3,5‐triazine (DCMT) in the presence of N‐methylmorpholine. It has been proved that synthesis proceeds via triazine active esters 3a,b, which are able to acylate carboxylate anion but not less nucleophilic carboxylic acid.     

Catalytic One-Pot Reductive Amination of Carboxylic Acids

The broad applications of primary alkyl amines in various fields have spurred extensive interests in synthetic organic chemistry. Recently, the reductive amination of carboxylic acids has become an attractive and practical strategy for synthesizing primary alkyl amines, due to their wide availability and bench stability. However, the inherent stability and higher oxidation state of carboxylic acids render this new strategy with new challenges. This Concept provides a summary of the recent advancements in the reductive aminations of carboxylic acids, specifically focusing on the catalytic tactics, underlying mechanisms, and applications in the synthesis of valuable products.     

Syntheses of Carboxylic Acids from 1, 1-Dichloroehylene

Many β-alkyl- and β-arylpropionic acids are readily obtainable by the reaction of secondary or tertiary alcohols, esters of these, or olefins with the inexpensive 1, 1-dichloroethylene in sulfuric acid. The success of the synthesis depends on the bulk and energy of the carbonium ion intermediate formed from the alcohols or olefins. With carbonium ions having one H atom attached to the carbonium C atom, electrophilic substitution of the 1,1-dichloroethylene takes place to a small extent. Dicarboxylic acids and carboxylic acids with higher molecular weights are sometimes formed as a result of side reactions.     

羧酸类化合物的结构和萃取性能的相关性

应用量子化学参数研究羧酸类化合物的结构与其萃取性能的相关性,并将二维结构参数应用到三维构效关系研究中,从而有效地改善了CoMFA法的结果,用pK_a值来表征羧酸类化合物的萃取性能.     

Polyvinylpyrrolidone-Supported Hydroperoxide for Selective Oxidation of Aldehydes to Carboxylic Acids and Sulfides to Sulfoxides

The facile immobilization of hydroperoxide on the cross-linked poly(vinylpyrrolidone) is described by treatment of a poly(vinylpyrrolidone)-Vilsmeier adduct with (35%) hydrogen peroxide. The in situ–generated poly(vinyl pyrrolidone)-supported hydroperoxide reagent showed very good performance in chemoselective oxidation of aldehydes to carboxylic acids as well as sulfides to sulfoxides.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.