Chemoselective organocatalytic aerobic oxidation of primary amines to secondary imines

Biomimetic aerobic oxidation of primary benzylic amines has been achieved by using a quinone catalyst. Excellent selectivity is observed for primary, unbranched benzylic amines relative to secondary/tertiary amines, branched benzylic amines, and aliphatic amines. The exquisite selectivity for benzylic amines enables oxidative self-sorting within dynamic mixtures of amines and imines to afford high yields of cross-coupled imine products.     

胺及其衍生物的非酰基化动力学拆分

光学纯胺在合成与药物化学领域都有着广泛的应用,发展其高效的合成方法一直以来是有机化学界的研究热点.其中通过N酰基化及去酰基化动力学拆分方法获得光学纯胺化合物,已经成为合成手性胺类化合物的重要方法.近年来,基于非酰基化(或去酰基化)的不对称反应实现外消旋胺的动力学拆分的报道不断涌现,包括一些氨基不参与反应的非酰基化(或去酰基化)不对称反应的外消旋胺的动力学拆分.根据氮原子是否参与反应以及反应类型的不同,总结了外消旋胺的化学催化动力学拆分的研究进展.     

Development of a General Non‐Noble Metal Catalyst for the Benign Amination of Alcohols with Amines and Ammonia

The N‐alkylation of amines or ammonia with alcohols is a valuable route for the synthesis of N‐alkyl amines. However, as a potentially clean and economic choice for N‐alkyl amine synthesis, non‐noble metal catalysts with high activity and good selectivity are rarely reported. Normally, they are severely limited due to low activity and poor generality. Herein, a simple NiCuFeO_x catalyst was designed and prepared for the N‐alkylation of ammonia or amines with alcohol or primary amines. N‐alkyl amines with various structures were successfully synthesized in moderate to excellent yields in the absence of organic ligands and bases. Typically, primary amines could be efficiently transformed into secondary amines and N‐heterocyclic compounds, and secondary amines could be N‐alkylated to synthesize tertiary amines. Note that primary and secondary amines could be produced through a one‐pot reaction of ammonia and alcohols. In addition to excellent catalytic performance, the catalyst itself possesses outstanding superiority, that is, it is air and moisture stable. Moreover, the magnetic property of this catalyst makes it easily separable from the reaction mixture and it could be recovered and reused for several runs without obvious deactivation.     

Palladium-catalyzed reaction of allyl carbamates; allylation of carbonucleophiles,and protection-deprotection of amines

Allylation of carbonucleophiles with allylic carbamates under neutral conditions has been studied. The C-allylation of carbonucleophile is competitive with the N-allylation of amines, and the structure of amines is crucial for the selectivity. Bulky secondary amines gave the best results. Also a new method of protection-deprotection of amines as carbamates has been developed. Smooth deprotection is possible by the palladium-catalyzed reaction of allyl carbamates with formic acid. This method is particulary useful for primary amines, including optically active amino acids.     

Blue Chitin Columns for the Extraction of Heterocyclic Amines from Urine Samples

During normal cooking of meat, a class of mutagenic/carcinogenic compounds called heterocyclic amines is formed. Heterocyclic amines are rapidly absorbed and metabolised in the human body, and for estimation of the intake of heterocyclic amines, it is useful to determinate their levels in the urine. Blue Chitin columns were used for the extraction and purification of heterocyclic amines from urine samples spiked with 14 different heterocyclic amines. The samples were analysed using LC-MS. The results show that Blue Chitin columns provide a straightforward and rapid means of extracting heterocyclic amines from urine samples, and that Blue Chitin column are also useful in the purification of urinary metabolites.     

Palladium catalysed 3-component cascade synthesis of bis(2-arylallyl) tertiary amines from aryl iodides,allene and primary amines

A 3-component cascade synthesis of bis(2-arylallyl) tertiary amines from aryl iodide, allene and primary aliphatic amines is described; chiral amines give analogous products with no detectable racemisation; mixtures of two different aryl iodides can be utilised to give the mixed tertiary amines as the sole, or major, product; the reaction is sensitive to stereoelectronic effects which lead to mono(2-arylallyl) secondary amines.     

Thermometric titrations of amines with nitrosyl perchlorate in acetonitrile solvent

Thirteen aliphatic and four aromatic amines, namely diethylamine, triethylamine, n-propylamine, di-n-propylamine, tri-n-butylamine, isopropylamine, di-isopropylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, aniline, N,N-dimethylaniline, 2-nitroaniline and 4-nitroaniline were titrated thermometrically with nitrosyl perchlorate in acetonitrile solvent. All the aliphatic amines gave very well-shaped thermometric titration curves. The calculated recovery values of the amines were very good. In comparison, the aromatic amines, aniline and N,N-dimethylaniline gave rather well-shaped titration curves, but the recovery values were fairly low. 2-Nitro- and 4-nitro anilines gave no thermometric response at all. The heats of reaction of the amines with nitrosyl perchlorate are rather high. However, the average heat of reaction of the aromatic amines is approximately two-thirds that of the average heat of the aliphatic amines. To support this method all the amines were also titrated potentiometrically and very similar results to those obtained with the thermometric method are seen. The nitrosyl ion is a Lewis acid, strong enough to titrate quantitatively aliphatic amines in acetonitrile solvent, but not strong enough to titrate aromatic amines at the required level in the same solvent.     

Reactions of the carbonate radical with aliphatic amines

Carbonate radicals react with aliphatic amines by a dual mechanism, viz. (i) hydrogen abstraction and (ii) electron transfer. The former is more probable with primary amines. Tertiary amines react via electron transfer. Both mechanisms may operate in secondary amines. Cyclic tertiary amines react with different rates and their relative reactivities are explained on the basis of the concept of Hoffmann's ‘through bond’ interaction.     

Chemospecific and ligand free CuI catalysed heterogeneous N-arylation of amines with diheteroaryl halides at room temperature

A ligand free, copper-catalyzed N-arylation reaction of amines with diheteroaryl halides in heterogeneous medium at room temperature has been developed. The protocol is very effective for low boiling amines and useful for amines available in aqueous solution. The reaction gives chemospecific arylation of amines with diheteroaryl halides in the mixture monoheteroaryl halides, diheteroaryl halides and carbocyclic aryl halides. The reaction is also chemospecific with respect to arylation of aliphatic amines. Monoarylated piperazines were also synthesized at room temperature following this protocol.     

在碲氢化钠作用下一步合成仲胺

本文报道合成仲胺的简便方法。在碲氢化钠(NaHTe)作用下,芳香族或脂肪族伯胺与醛反应,一步生成相应的仲胺。     

伯胺的单烷基化反应研究进展

伯胺的单烷基化在有机合成过程中是非常重要的一类反应。由于伯胺的化学性质较活泼,对其进行烷基化时很难控制在仲胺阶段而易于生成叔胺,因而其单烷基化一般通过间接的方法得到。本文介绍了伯胺单烷基化方法的最新研究进展。     

Fast naked-eye detection of amines with viologen derivatives

Three viologen derivatives with the ability to detect amines were synthesised. Upon interacting with amines, a rapid colour change caused by electron transfer and charge transfer between viologen derivatives and amines can be directly observed by naked eyes. With fluorine substituents, the detection sensitivity of these viologen derivatives for amines is remarkably enhanced to reach the level of ppm.     

Facile N‐Alkylation/N′‐Arylation Process: A Direct Approach to Aromatic Aminoalkyl Amines

An intriguing C?N transformation involving a catalyst‐free N‐alkylation/N′‐arylation process in a multicomponent reaction with secondary amines, cyclic tertiary amines and electron‐deficient aryl halides has been described. In this case, the N‐alkylation of secondary amines, utilizing cyclic tertiary amines as alkyl group sources, is enabled by a facile C?N cleavage. Such an operationally simple method could facilitate access to aromatic aminoalkyl amines, nitrogen‐containing bioactive molecules, in good to excellent yields.     

Reaction of Thiocarbonyl Fluoride Generated from Difluorocarbene with Amines

The reaction of thiocarbonyl fluoride, generated from difluorocarbene, with various amines under mild conditions is described. Secondary amines, primary amines, and o ‐phenylenediamines are converted to thiocarbamoyl fluorides, isothiocyanates, and difluoromethylthiolated heterocycles, respectively. Thiocarbamoyl fluorides were further transformed into trifluoromethylated amines by using a one‐pot process. Thiocarbonyl fluoride is generated in situ and is rapidly fully converted in one pot under mild conditions; therefore, no special safety precautions are needed.     

Morphology evolution of ZnO by controlling solvent and electrochemical sensing of hexagonal nanotablets toward amines

Organic amines are important solvent and raw material in laboratory and industry, as well as releasing from cigarette smoke. It is significant to detect low-concentration amines for environment and public health. Here we reported that as-synthesized zinc oxide is an effective electrode material of electrochemical sensor for the detection of amines. The characterization results reveal that the ZnO morphologies experienced a change from hexagonal bowl-like microparticles, cones, prisms to nanoparticles by adjusting the reaction time, temperature, solvents and additives. Interestingly, ZnO material possessing hexagonal shapes and different sizes exhibits distinct electrochemical response in various amines solution, suggesting that there is a better dependent relationship between different morphological ZnO and amines detection. Particularly, regular hexagonal ZnO nanotablets exhibit a detectable electrochemical response and selectivity to ammonia, implying it can be serve as electrode material for highly effective detection of organic amines.     

Oxidative amide synthesis directly from alcohols with amines

Transition metal catalyzed oxidative amide synthesis directly from primary alcohols and amines is a highly atom economical transformation that evolves hydrogen gas as the only by-product. Several Ru-, Rh-based homogeneous and Ag-based heterogeneous catalysts have been developed for direct amide synthesis. Most of the developed catalysts showed excellent activity with sterically unhindered alcohols and amines; however, limited activity was observed with sterically hindered alcohols or amines, less basic aryl amines, and secondary amines. This account provides an overview of recent advances and challenges in direct amide synthesis.     

多相双金属Pt-Sn/γ-Al_2O_3催化的胺N-烷基化反应合成仲胺和叔胺

基于借氢策略、醇为烷基化试剂的胺的N-烷基化反应是合成胺类化合物的绿色途径.在无外加氢源条件下,多相双金属Pt-Sn/γ-Al2O3催化剂可高效催化醇为烷基化试剂的伯(仲)胺的N-烷基化反应合成仲(叔)胺,反应副产物为水与极少量亚胺.催化体系的底物适应性好,目标产物收率高;催化剂可以循环使用,具有潜在的工业化应用前景.     

Selective N-alkylation of amines using nitriles under hydrogenation conditions: facile synthesis of secondary and tertiary amines

Nitriles were found to be highly effective alkylating reagents for the selective N-alkylation of amines under catalytic hydrogenation conditions. For the aromatic primary amines, the corresponding secondary amines were selectively obtained under Pd/C-catalyzed hydrogenation conditions. Although the use of electron poor aromatic amines or bulky nitriles showed a lower reactivity toward the reductive alkylation, the addition of NH(4)OAc enhanced the reactivity to give secondary aromatic amines in good to excellent yields. Under the same reaction conditions, aromatic nitro compounds instead of the aromatic primary amines could be directly transformed into secondary amines via a domino reaction involving the one-pot hydrogenation of the nitro group and the reductive alkylation of the amines. While aliphatic amines were effectively converted to the corresponding tertiary amines under Pd/C-catalyzed conditions, Rh/C was a highly effective catalyst for the N-monoalkylation of aliphatic primary amines without over-alkylation to the tertiary amines. Furthermore, the combination of the Rh/C-catalyzed N-monoalkylation of the aliphatic primary amines and additional Pd/C-catalyzed alkylation of the resulting secondary aliphatic amines could selectively prepare aliphatic tertiary amines possessing three different alkyl groups. According to the mechanistic studies, it seems reasonable to conclude that nitriles were reduced to aldimines before the nucleophilic attack of the amine during the first step of the reaction.     

脂肪酶催化作用下酰胺化反应的立体规则性研究

提出了在LipasefromCandidaAntrarctica(CAL)脂肪酶的催化作用下,含有手性中心C原子的胺类化合物酰胺化的异构选择性规则.与氨基相连的碳原子的立体结构对酰胺化反应有很大的影响.型胺类化合物呈R-型优先选择,型胺类化合物呈S-型优先选择.     

Enthalpies of formation of primary, secondary, and tertiary amineborane adducts in tetrahydrofuran solution

The enthalpies of solution of primary, secondary, and tertiary amines in THF were determined from calorimetric experiments for five primary, five secondary, and three tertiary amines. The enthalpies of formation of amineborane adducts from borane and the corresponding amines in THF solution were also determined. The differences in adduct formation enthalpies from borane and the corresponding amines can be explained by taking into account steric effects and the chain length of the substituents on the amine. In general, as the alkyl chain length, branching, or the number of chains increases, the formation enthalpy of amineborane adducts is less exothermic. That is to say, the steric effect is more important in tertiary and secondary amines than in primary ones. The enthalpy of solution of linear primary amines in THF was more endothermic as the alkyl chain increased and a similar behavior was observed with linear secondary and tertiary ones. An analysis is made of the amine structural factors which affect the amineborane adduct formation.