首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
The use of chiral secondary amines containing only one branched substituent has been shown to give optimal yields and stereoselectivities in the preparation of α-amino acids using the Petasis reaction. While the use of chiral primary amines generally gives products in low to moderate diastereoselectivity, chiral secondary amines generally give products in >95:5 diastereoselectivity. Additionally, the use of amines with two chiral (and by definition, branched) N-alkyl substituents results in significantly reduced yields with respect to to secondary amines with one or no branched N-alkyl substituents.  相似文献   

2.
To find a useful, practical, and ecologically safer way to synthesize protected amines, the reactions of amines with benzyl halides under CO2 atmosphere were systematically examined. For primary amines, the CO2‐inserted products were obtained in higher yields in the presence of DBU as a base, under a high pressure of CO2, and in a low‐polarity solvent (toluene/hexane 1 : 1). Secondary amines gave only low yields of CO2‐inserted products.  相似文献   

3.
The reaction of [di(acyloxy)iodo]benzene with secondary phosphine oxides or H‐phosphinates in the presence of primary or secondary amines allows one to obtain phosphinic or phosphonic acids amides in the one‐pot process. We take advantage of the strong acylating system DAIB/R2P(O)H to phosphinylation of amines. However, the reaction mechanism is multipathway and causes yields of phosphinic or phosphonic acids amides to be moderate. When the concentration of amines is low, the intermolecular process plays a main role leading to the formation of carboxylic amides through mixed phosphoric–carboxylic anhydride, and also in the low concentration of amines, tetrahydrofuran effectively competes with the amines in the nucleophilic attack on the acylating intermediates. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:81–86, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20514  相似文献   

4.
The nucleophilic substitution by primary amines of secondary homoallylic mesylates easily obtained from corresponding alcohols offers a convenient way to prepare homoallylic amines. The relative low yields in pure compounds is counterbalanced by the simplicity of the procedure.  相似文献   

5.
在低价钛试剂 (TiCl4/Sm)作用下取代苯乙酮肟发生脱肟反应生成酮 ,而在同样条件下 ,二芳酮肟则生成二芳酮、胺或希夫碱  相似文献   

6.
A substitution reaction of amines with alcohols for N-alkylated amines has been developed using inexpensive AlCl_3 without any ligand or additive.Either aromatic or aliphatic amines and primary or secondary alcohols perform the AlCl_3-mediated reaction smoothly to afford various N-alkylated amines in satisfactory yields.  相似文献   

7.
梁学正  张敬  鲍少华  杨建国 《中国化学》2009,27(7):1221-1224
提供了一种新型高效的催化缺电子烯与胺类的共扼加成的反应体系。首先合成了一系列负载型氟化钾固体碱,并用于催化上述反应。通过对不同载体选择考察,筛选出氟化钾负载氧化镁固体碱为最佳催化剂。在进一步的催化反应过程中发现,该催化剂对反应具有很高的催化活性,能催化该反应在短短数分钟内完成。操作简单方便,不需要任何溶剂,催化剂价格低廉,反应收率高,可重复使用,具有化学选择性,适用范围广泛等均为该催化体系的主要特征。  相似文献   

8.
A nickel(0) species catalyzes the five-component connection reaction of dimethylzinc, alkynes, 1,3-butadiene, aldehydes, and amines, furnishing either 1 or 2 selectively in good yields depending on the kinds of amines, aromatic or aliphatic amines, respectively.  相似文献   

9.
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 NiCuFeOx 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.  相似文献   

10.
A rapid Michael addition of secondary amines to α, β-unsaturated carbonyl compounds has been achieved in good to excellent yields in the presence of water under microwave irradiation. In the absence of water and under conventional method the reaction does not proceed or take place in very low yield after a long reaction time.  相似文献   

11.
We report a fluorogenic probe that is able to discriminate a range of primary or secondary biogenic amines and their natural or synthetic mimics, in water or buffer, by means of the turn-on transient generation of green fluorescence, with high quantum yields and low detection limits, thus making the system suitable for the detection of abuse drugs, such as MDMA, from ecstasy tablets.  相似文献   

12.
Reactions of 2,2-dihydropolyfluoroalkylaldehydes (1) with amines (2) were studied. Both aliphatic amines and electron-deficient aromatic amines readily reacted with 1 in acetonitrile and water under reflux to give fluoroalkyl enaminoketones (3) in high yields, while no condensed products were obtained by reactions of 1 with electron-rich aromatic amines under similar conditions. In the presence of triethylamine, however, the reaction of 1 with electron-rich aromatic amines at room temperature gave 3 in low yields.  相似文献   

13.
Summary The salicylaldehyde method for the differentiation of primary and secondary amines in mixtures has been critically evaluated. This method yields best results in acetonitrile. In mixtures of amines one can expect high results for the primary amine with correspondingly low results for the secondary amine. Corrections can be made with known mixtures of the amines.Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore Laboratory under contract number W-7405-ENG-48.  相似文献   

14.
The novel efficient procedure has been developed for the conjugate addition of amines to electron deficient alkenes using the novel SO3H functionalized ionic liquid as catalyst. The results showed that the novel catalyst owned high activities for the reactions with excellent yields within several minutes. Various amines and electron deficient alkenes were successfully transformed to the corresponding products in the catalytic system. Operational simplicity, without need of any solvent, low cost of the catalyst used, room temperature, high yields, reusability, excellent chemoselectivity and wide applicability are the key features of this methodology.  相似文献   

15.
Alcohols are solvents of choice to react boronates, aldehydes and either primary or secondary amines. Thus, while the reaction proceeds sluggishly, or not at all, in aprotic solvents, the desired aminoacids are in most cases obtained in high yields when conducted in methanol or hexafluoro-iso-propanol. In the case of secondary amines, microwave activation is shown to strongly accelerate the process without altering the yields.  相似文献   

16.
The palladium-catalyzed coupling of C-5 iodopyrimidine nucleosides; 1,2-, 1,3-, or 1,ω-dienes; and amines provides a novel and efficient method for the preparation of a wide variety of C-5 aminoalkyl-substituted nucleosides. Adding certain Lewis acids, particularly zinc salts, improves the yields significantly. Secondary amines are the most effective amines for this process. Acyclic and cyclic dienes have been successfully employed. Protection of the 3′- and 5′-hydroxyl groups of iodouridine is required in order to obtain good yields when the coupling process is carried out on 1,3-dienes or long chain or branched non-conjugated dienes.  相似文献   

17.
Synthesis of amino-sugars using reductive amination reactions. Preliminary communication Treatment of aldehydo- or keto-sugars with primary or secondary amines and hydrogen in the presence of a catalyst (Pd/C) gave with good to excellent yields (67–96%) the expected secondary or tertiary amines. Primary amines can be obtained by using benzylamine, a hydrogenolysis taking place during the reaction.  相似文献   

18.
An efficient copper-catalyzed method for N-arylation of amines has been developed with part-per-million catalyst loadings at room temperature under air. Reactions of substituted (E)-1-(2-halophenyl)alkanone oximes with aliphatic amines or aromatic amines provided the N-arylation products in good to excellent yields.  相似文献   

19.
The azides were reduced to the corresponding amines by two new meml/LEwis acid systems in water or in aqueous EtOH in yields ranging from 80%-95%. The reaction rates were faster in water than in aqueous EtOH in most cases. All 16 azides with different functional groups were well reduced to the corresponding amines in excellent yields and reaction rates.  相似文献   

20.
We present an efficient, simple, metal‐ and solvent‐free silica‐gel‐promoted synthesis of functionalized conjugated dienes by sequential aza‐Michael/Michael reactions by starting from commercially available primary amines and propiolic esters. The scope and usefulness of the method is demonstrated for 31 examples, including a range of propiolic esters, aliphatic amines, and differently substituted aromatic amines. For aliphatic amines, the products were obtained within 0.5 to 4 h in 52 to 85 % yield, compared with 3.5 to 22 h under classical solution‐phase synthesis, which proceeds with similar or lower yields. The method was found to be particularly useful for weakly nucleophilic aromatic amines, which provided products in 21 to 73 % yield over 2.5 to 9.5 h compared with yields of 0 to 49 % over 1 to 6 d under standard solution‐phase conditions, and for more hydrophobic esters that gave products in yields of 47 to 79 % over 1 to 3 h compared with 0 to 45 % over 4 to 114 h in solvent.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号