硝基化合物的还原羰基化反应

硝基化合物与ＣＯ之间进行的还原羰基化反应是有机催化的新研究领域。通过硝合物的还原羰基化反应可以合成许多重要的含氮有机化合物吉异氰酸酯，氨基甲酸酯，脲，偶氮化合物和Ｎ－杂环化合物等。本文就还原羰基化反应，催化剂及催化作用机理的研究进展作一评述，其中也提及我们实验的研究工作。     

非对称取代脲的合成与应用

总结了合成非对称取代脲的几种方法，分析了各种方法的利弊，介绍了非对称 取代脲的主要应用，指出直接利用一氧化碳进行硒催化的胺与硝基化合物的氧化还 原羰基化反应来合成非对称取代脲的方法是比较有发展前景的方法，并对硒催化的 氧化还原羰基化反应作了较为详细的介绍。     

硒催化法合成2-吡啶脲的研究

 采用硒催化的一氧化碳还原羰基化法,由硝基苯衍生物与2－氨基吡啶进行反应,得到的不是比例相当的三种脲类物质混合物,而主要得到非对称的吡啶脲．进一步发展了硒／一氧化碳催化体系对硝基化合物的还原羰基化法,可望用来合成一系列含取代基的苯基吡啶基脲类物质;该合成方法工艺简单,操作易行．对部分产物进行了红外光谱、核磁共振谱、高压液相色谱及元素分析等鉴定．     

硒催化的邻硝基苯胺类化合物的羰基化反应

用硒作催化剂，三乙胺为助催化剂，CO为羰基化试剂，通过氧化还原羰基化的方法，将邻硝基苯胺类化合物在分子内羰基化成环，反应生成相应的一系列环脲类物质，此催化合成方法的反应选择性近秋100％，收率较高，操作简单，并提出了可能的反应机理。     

硒催化4-氨基吡啶与硝基芳烃羰基化合成4-吡啶基脲

以非金属硒为催化剂,三乙胺为助催化剂,用CO替代剧毒光气作为羰基化试剂,通过鼓泡方式经硒催化"一锅煮"的4-氨基吡啶与硝基芳烃的氧化还原羰基化反应合成4-吡啶基脲.通过探究反应温度、反应时间、溶剂及碱的种类等因素的影响,获得了反应的优化条件.在优化条件的基础上,以中等到良好的收率制得4-吡啶基脲类化合物,反应底物硝基芳烃的普遍适用性较好;还提出了该反应的可能机理.     

胺氧化羰基化合成脲的研究进展

CO是一种廉价、丰富且有用的C1分子,将其作为羰基源参与胺氧化羰基化反应是有机化学中一类重要的反应.近年来,采用胺氧化羰基化合成脲类化合物的技术路线备受关注.我们综述了催化剂参与的胺氧化羰基化合成脲类化合物的研究现状,还对胺氧化羰基化反应的发展趋势进行了展望.     

硒催化的乙二胺、乙醇胺和环胺的氧化羰基化反应

研究了以硒粉作催化剂,一氧化碳为羰基化试剂的乙二胺、乙醇胺和一些环胺的羰基化反应,考察了氧化剂对反应的影响。发现氧气是该反应较好的氧化剂,而没有氧化剂存在时,几乎没有羰基化反应发生。在硒／氧化剂体系存在下,乙二胺和乙醇胺这样一些分子内具有相邻两个亲基团物质的羰基化反应易趋向于分子内羰基化形成较为稳定的五元环产物,产率和选择性较高;而环胺如哌啶和吗啡啉的羰基化可生成相应的四取代脲产物。对反应机理进行     

硒催化反应最新研究进展

价廉易得的非金属硒作催化剂不但具有良好的催化活化CO的性能及反应过程相转移催化特性, 而且能循环使用. 用Se/CO催化体系替代贵金属催化羰基化法及剧毒的光气法进行羰基化反应及用Se/CO/H2O催化体系进行高选择性的还原反应, 具有反应条件温和、原子经济性高、成本低、环境友好、路线简短、后处理方便等优点, 因而引起人们的广泛关注. 概述了近几年来硒催化羰基化反应和硒催化选择性还原反应的最新研究进展, 并对硒催化反应的发展趋势进行了展望.     

钯催化芳基偶氮的氧化羰基化反应

采用TBHP作为氧化剂,发展了钯催化芳基偶氮化合物N＝N双键断裂的氧化羰基化反应.芳基偶氮的羰基化反应在Pd(OAc)2(5％),MeO-BIPHEP (5％),芳基偶氮(0.2 mmol),TBHP(2 equiv),H2O(1 equiv),DCE(1 mL),CO (3.0 MPa)的条件下110℃反应12h后,经柱层析纯化分离得到31％-91％的芳基脲.初步的机理研究表明,芳基偶氮化合物的N＝N双键断裂原位产生芳基胺,再进一步氧化羰基化生成芳基脲.     

2-硒代咪唑类化合物催化CO与胺的羰基化反应

首次研究了2-硒代咪唑类化合物催化的一氧化碳对胺的羰基化生成对称脲或噁唑啉-2-酮的反应,目标产物收率中等到良好.与传统的单质硒催化的羰基化反应相比,新催化体系有效避免了有恶臭气味的含硒化合物的产生.     

New and direct route to 5-trifluoromethyl-5,6-dihydrouracils by means of palladium complex catalyzed “ureidocarbonylation” of 2-bromo-3,3,3-trifluoropropene

Palladium complex catalyzed carbonylation of 2-bromo-3,3,3-trifluoropropene (2-Br-TFP) with ureas afforded 5-trifluoromethyl-5,6-dihydrouracils in moderate to good yields, which were converted into 5-trifluoromethyluracils in nearly quantitative yields.     

非光气含氮化合物催化羰化研究进展

本文对近几年来非光气含氮化合物羰化合成氨基甲酸酯及二取代脲的方法进行了概述,主要包括使用钯、钌、铑、硒、金等催化体系以一氧化碳为羰化剂进行的催化氧化羰化和催化还原羰化反应过程,以及使用碱催化体系以二氧化碳和碳酸二甲酯等为羰化剂的反应过程和机理.     

钯催化胺的羰基化反应

综述了钯催化胺的单，双羰基化反应以及钯催化胺基化反应工业及有机合成中的应用，同时对羰基化反应新进展－超临界二氧化碳流体作为反应介质也作了综述。     

Nitrogen-containing organobases as promoters in the cobalt(II)-Schiff base catalyzed oxidative carbonylation of amines

The use of organic bases as promoters in the cobalt(II)-Schiff base complex catalyzed oxidative carbonylation of amines was investigated. The generality of the reaction was also studied by submitting different amines to the same procedure and by changing the reaction conditions. Very good yields in the corresponding ureas were achieved in toluene with a catalyst loading of 0.5 mol % and using TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene) as promoter. Methyl carbamates were obtained in methanol.     

Palladium-catalyzed N-acylation of monosubstituted ureas using near-stoichiometric carbon monoxide

The palladium-catalyzed carbonylation of urea derivatives with aryl iodides and bromides afforded N-benzoyl ureas (20 examples) in yields attaining quantitative via the application of near-stoichiometric amounts of carbon monoxide generated from the decarbonylation of the CO precursor, 9-methylfluorene-9-carbonyl chloride. The synthetic protocol displayed good functional group tolerance. The methodology is also highly suitable for (13)C isotope labeling, which was demonstrated through the synthesis of three benzoyl ureas, including the insecticide triflumuron, whereby (13)CO was incorporated into the core structure.     

Selective and environmentally friendly methodologies based on the use of electrochemistry for fine chemical preparation: an efficient synthesis of N,N'-disubstituted ureas

A novel efficient synthesis of N,N'-disubstituted ureas has been developed. Aromatic and aliphatic primary amines undergo oxidative carbonylation under atmospheric pressure of carbon monoxide using Pd(II) catalyst in combination with its anodic recycling at a graphite electrode.     

Efficient synthesis of ureas by direct palladium-catalyzed oxidative carbonylation of amines

A general synthesis of symmetrically disubstituted ureas and trisubstituted ureas by direct Pd-catalyzed oxidative carbonylation of primary amines or of a mixture of a primary and a secondary amine, respectively, with unprecedented catalytic efficiencies for this kind of process, is reported. Reactions are carried out at 90-100 degrees C in DME as the solvent in the presence of PdI(2) in conjunction with an excess of KI as the catalytic system and under 20 atm of a 4:1 mixture of CO and air. In some cases, working in the presence of an excess of CO(2) (40 atm) in addition to CO and air (60 atm total) had a beneficial effect on substrate reactivity and product yield. Cyclic five-membered and six-membered ureas were easily formed from primary diamines. The methodology has been successfully applied to the synthesis of pharmacologically active ureas, such as those deriving from alpha-amino esters or urea NPY5RA-972, a potent antagonist of the neuropeptide Y5 receptor.     

A Convenient Palladium‐Catalyzed Reductive Carbonylation of Aryl Iodides with Dual Role of Formic Acid

Palladium‐catalyzed reductive carbonylation of aryl halides represents a straightforward pathway for the synthesis of aromatic aldehydes. The known reductive carbonylation procedures either require CO gas or complexed compounds as CO sources. In this communication, we developed a palladium‐catalyzed reductive carbonylation of aryl iodides with formic acid as the formyl source. As a convenient, practical, and environmental friendly methodology, no additional silane or H₂ was required. A variety of aromatic aldehydes were isolated in moderate to excellent yields under mild reaction conditions. Notably, this is the first procedure on using formic acid as the formyl source.