- N-Heterocyclic carbene (NHC) catalyzed chemoselective acylation of alcohols in the presence of amines with various acylating reagents
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This edge article reports the synthesis and full characterization including X-ray analysis of three different acylazolium ions. The reactivity of these acylazolium ions as acylating reagents of amines and alcohols is discussed. Whereas benzylamine slowly reacts with the acylazolium ions, benzyl alcohol acylation does not occur. However, upon activation of the alcohol with an N-heterocyclic carbene (NHC) as catalyst, efficient esterification is achieved. Importantly, benzylester formation is obtained in the presence of benzylamine upon selective alcohol activation by the NHC. High level DFT calculations reveal that alcohol activation occurs by strong H-bond formation between the NHC and the alcohol thereby increasing the nucleophilicity of the alcohol. For oxidatively generated acylazolium ions under NHC catalysis, the carbene has a dual role (cooperative catalysis): (a) the NHC is used for generation of the acylazolium ion and (b) the NHC is used for activation of the alcohol in the subsequent acylation step. NHC-catalyzed selective acylation of benzyl alcohol in the presence of benzylamine can also be achieved with trifluoroethyl and hexafluoroisopropylesters as acylation reagents. Moreover, an enol acetate also shows high O-selectivity as a chemoselective acetylation reagent. Kinetic and mechanistic studies are provided and some examples of the chemoselective acylation of amino alcohols are presented.
- Samanta, Ramesh C.,De Sarkar, Suman,Froehlich, Roland,Grimme, Stefan,Studer, Armido
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p. 2177 - 2184
(2013/05/21)
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- N-palmitoylethanolamide derivatives: Synthesis and studies on anticonvulsant and antidepressant activities
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A series novel of N-palmitoylethanolamide derivatives was synthesized and screened for their anticonvulsant and antidepressant activities. Anticonvulsant activities and neurotoxicities of compounds when injected intraperitoneally (i.p.) were determined by maximal electroshock seizure (MES) test and a rotarod test, respectively, in mice. Only four of the synthesized compounds (3a, 3b, 3c, and 3d) showed anticonvulsant activity at a dose of 100 mg/kg. Six compounds showed reduced immobility durations during the forced swimming test at a dose of 10 mg/kg, indicative of antidepressant activity. Among the compounds, N-(3-hydroxypropyl)cinnamamide (3a) was the most promising compound and significantly reduced the duration of immobility duration by 23.36% at a dose of 10 mg/kg compared with the control (P0.01). Springer Science+Business Media, LLC 2010.
- Guan, Li-Ping,Sui, Xin,Deng, Xian-Qing,Zhao, Dong-Hai,Qu, You-Le,Quan, Zhe-Shan
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experimental part
p. 601 - 606
(2012/04/10)
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