锆氢催化的酰胺硼氢化合成胺类化合物研究:机理、使用范围和应用

发展温和条件下胺类化合物的高效合成方法是催化与合成领域长期研究的课题.其中,酰胺还原因其原料来源广、易于合成而广受关注.酰胺还原到胺需要选择性断裂C=O键,因此该反应具有很大的挑战性.传统酰胺还原方法需要使用当量的强还原试剂,如四氢铝锂、硼氢化钠等,且官能团兼容性较差.使用氢气还原原子经济性最高,也最有吸引力;然而,目前已报道的体系大都在高温(>120℃)或高压(>40 bar H2)的条件下进行.虽然催化硼氢化可以在温和的条件下将羰基化合物还原,但由于酰胺化合物惰性比较高,其选择性的催化硼氢化研究则相对较少,而且在温和条件下对三级、二级、一级酰胺都适用的例子依然非常有限.本文采用前过渡金属锆氢催化剂实现了室温条件下酰胺选择性硼氢化制备胺类化合物,并进行了详细的机理研究.原位红外监测到反应过程中酰胺和硼烷逐渐减少,目标产物逐渐增多;但并未给出其他反应中间体的信息.核磁研究以及对照实验结果表明,反应中有苯甲醛的生成,可能是反应中间体.因此推测,该催化体系经历了锆氢介导的酰胺C?N键断裂、重组、C?O键断裂这一特殊的酰胺键活化转化过程.DFT计算也证实了上述反应历程的可行性.除一些常见官能团外,本方法对羧酸酯、氰基、硝基、烯烃和炔烃这些可能被硼氢化的官能团同样具有兼容性.而且本文体系对一些生物、药物分子衍生酰胺的硼氢化也可以顺利进行.可见,本文发展了一种温和条件下使用廉价催化剂和原料选择性合成胺类化合物的方法.     

锆、钛介导的烯烃、炔烃硼氢化（英文）

过渡金属催化的烯烃、炔烃硼氢化反应是制备硼酸酯类化合物最为有效的方法之一,该反应具有100%的原子经济性,原料简单易得,产物多样性可调等优点.已知的金属催化剂大都依赖于铑、铱、钯、铂、钴、铁、铜等后过渡金属,而使用前过渡金属锆、钛作为催化剂的反应体系则鲜有报道.总结了锆、钛介导的(化学计量与催化量)烯烃、炔烃硼氢化反应的研究现状,并对今后锆、钛催化的烯烃、炔烃硼氢化反应的发展进行了展望.     

过渡金属催化下的烯烃硼氢化反应

本文综述了在过渡金属尤其是铑络合物催化下烯烃与CB的硼氢化反应在化学、位置和立体选择性的进展,对它们的机理也进行了讨论。     

联吡啶配体促进铬催化炔烃的顺式硼氢化反应（英文）

报道了金属铬催化炔烃的硼氢化反应.廉价易得的三氯化铬在4,4’-二叔丁基-2,2’-联吡啶配体及单质镁的还原作用下表现出高反应活性,催化实现了频哪醇硼烷与炔烃加成的硼氢化反应,为室温条件下制备烯基硼化合物提供了一条有效的合成策略.     

锌-锂双金属化合物的合成及其在异腈酸酯硼氢化中的催化应用

有关异腈酸酯硼氢化反应的报道极其稀少,迄今为止,锌金属化合物催化的异腈酸酯硼氢化反应尚未见报道.介绍了一种结构新颖的不对称β-二亚胺锌-锂双金属化合物的合成方法,并将其作为高效催化剂成功应用于一系列带有不同官能团的异腈酸酯和频哪醇硼烷的硼氢化反应中,同时对硼氢化反应机理进行了初步探索.     

载钯磷酸锆的制备和催化性能研究

本文制备了载钯磷酸锆，作为由丙酮和氢气一步法合成甲基异丁基甲酮（ＭＩＢＫ）的催化剂．考察了制备时的ｐＨ对催化剂比表面积、酸度、酸强度以及催化性能的影响．     

酶催化合成酰胺类化合物的研究进展

酰胺官能团具有重要的药理作用,是许多生物活性物质的关键结构单元。据报道,超过25%的已知药物中含有酰胺键结构。研究与发展酰胺类化合物的高效合成方法始终是制药行业的重要任务之一。近年来,生物催化技术的发展为酰胺键的构建提供了一种较为经济绿色的合成方法,丰富了酰胺类化合物的合成策略。本文综述了生物酶催化合成酰胺类化合物的相关研究进展。     

过渡金属催化下的烯烃硼氢化反应

本文综述了在过渡金属尤其是铑络合物催化下烯烃与CB ( 邻苯二酚硼烷 ) 的硼氢化反应在化学、位置和立体选择性的进展, 对它们的机理也进行了讨论。     

胍基锆酰胺配合物与四氯化碳的反应生成氯化锆胍基衍生物

四氯化碳与Zr（NMe₂）₂[ⁱPrNC（NMe₂）NⁱPr]₂（1）反应先生成中间体ZrCl（NMe₂）₂[ⁱPrNC（NMe₂）NⁱPr]₂（2）,然后生成ZrCl₂[ⁱPrNC（NMe₂）NⁱPr]₂（3）。该反应可能是自由基反应。另外,配合物2可由ZrCl（NMe₂）₃与二异丙基碳二亚胺ⁱPr-N=C=N-ⁱPr反应制备。对配合物2进行了核磁共振（NMR）和元素分析。     

A novel synthesis of tocopheryl amines and amides

We report the synthesis of tocopheryl amines and amides from commercially available tocopherols. This synthesis improves the yield and diastereomeric purity of these biologically important compounds. The tocopheryl amines were prepared from the corresponding α- and δ-tocopherols using two distinct synthetic routes. The introduction of the C(6)-amino group can be achieved by aryl nitration/reduction or by Pd-catalyzed substitution of an aryl triflate, depending on the structure of the starting material. We also prepared the succinamide and maleamide derivatives of each amine. Tocopheryl amides are more potent pro-apoptotic anti-cancer agents than the corresponding α-tocopheryl esters. These compounds act selectively within the mitochondria of cancer cells.     

Diisobutylaluminum borohydride: An efficient reagent for the reduction of tertiary amides to the corresponding amines under ambient conditions

A synthetically simple mixed metal hydride, diisobutylaluminum borohydride [(iBu)₂AlBH₄], is easily generated from a 1:1 mixture of borane-dimethylsulfide (BMS) and diisobutylaluminum hydride (DIBAL). The reduction of tertiary amides using (iBu)₂AlBH₄ is complete within five minutes under ambient conditions and the product tertiary amines were isolated in 70–99% yields by a simple acid-base extraction. This new methodology, reported herein, works well for reduction of tertiary aliphatic and aromatic amides as well as lactams to the corresponding amines and product isolation and purification does not require column chromatography.     

Catalyzed hydroboration of nitrostyrenes and 4-vinylaniline: a mild and selective route to aniline derivatives containing boronate esters

Transition metal catalyzed reactions of catecholborane (HBcat; cat = 1,2-O₂C₆H₄) with β-nitrostyrene and 3-nitrostyrene lead to products derived from competing hydrogenation and hydroboration of the alkene unit along with reduction of the nitro group. Hydroboration of 4-vinylaniline gave regioselective formation of either the branched or the linear organoboronate ester depending upon the catalyst precursors (i.e., RhCl(PPh₃)₃ or Rh(acac)(dppe) vs [Cp^∗IrCl₂]₂) used to facilitate this reaction. Hydroboration products were converted to air-stable primary amines by addition of pinacol.     

One-step conversion to tertiary amines: InBr3/Et3SiH-mediated reductive deoxygenation of tertiary amides

We have developed a simple and practical procedure for a direct reductive conversion from a variety of tertiary amides to the corresponding tertiary amines using an InBr₃/Et₃SiH reducing system. This reducing system can be applied to the reduction of a secondary amide and provides a more efficient alternative to conventional methods that use aluminum and boron hydrides.     

A novel approach for the synthesis of aryl amides

A novel and highly efficient approach for the synthesis of aryl amides in high yields by the reaction of carboxylic acids and isocyanides in methanol at ambient temperature is reported.     

Graphene oxide (GO) catalyzed transamidation of aliphatic amides: An efficient metal-free procedure

Transamidation involves direct interconversion of an amide with amine, and represents an alternative to the common method of amide formation from the reaction of carboxylic acid with an amine. While the carboxamides have huge potential in biological systems and polymer industries, their formation from carboxylic acids requires activation by a suitable catalyst. A metal-free transamidation of aliphatic amide with aromatic amine catalyzed by graphene oxide (GO) has been developed and established as a general, synthetically useful and selective procedure. Graphene oxide bearing several carboxylic acids on the edges and having large surface area acts as an efficient and recyclable catalyst for transamidation.     

Metal-free synthesis of amides by oxidative amidation of aldehydes with amines in PEG/oxidant system

A simple, inexpensive, and efficient one-pot synthesis of amide derivatives were achieved in good to excellent yields via the directly oxidative amidation of aldehydes with amines under PEG/Oxidant system.     

Synthesis and molecular structures of lanthanocene amide complexes and their catalytic activity for addition of amines to nitriles

Reaction of (CH₃C₅H₄)₂LnCl(THF) with NaNHAr in a 1:1 molar ratio in THF afforded the amide complexes (CH₃C₅H₄)₂LnNHAr(THF) [(Ar = 2,6-Me₂C₆H_3, Ln = Yb (I), Y (III); Ar = 2,6-ⁱPr₂C₆H₃, Ln = Yb (II)]. X-ray crystal structure determination revealed that complexes I-III are isostructural. The central metal in each complex coordinated to two methylcyclopentadienyl groups, one amide group and one oxygen atom from THF to form a distorted tetrahedron. Complexes I-III and a known complex (CH₃C₅H₄)₂YbNⁱPr₂(THF) IV all can serve as the catalysts for addition of amines to nitriles to monosubstituted N-arylamidines. The activity depended on the central metals and amide groups, and the active sequence follows the trend IV ≈ III < I < II.     

Ruthenium‐Catalyzed Reductive Arylation of N‐(2‐Pyridinyl)amides with Isopropanol and Arylboronate Esters

A new three‐component reductive arylation of amides with stable reactants (iPrOH and arylboronate esters), making use of a 2‐pyridinyl (Py) directing group, is described. The N‐Py‐amide substrates are readily prepared from carboxylic acids and PyNH₂, and the resulting N‐Py‐1‐arylalkanamine reaction products are easily transformed into the corresponding chlorides by substitution of the HN‐Py group with HCl. The 1‐aryl‐1‐chloroalkane products allow substitution and cross‐coupling reactions. Therefore, a general protocol for the transformation of carboxylic acids into a variety of functionalities is obtained. The Py‐NH₂ by‐product can be recycled.