دانلود رایگان ترجمه مقاله تاثیر اسید لوئیس در سنتز ایندول Nenitzescu – الزویر 2008
دانلود رایگان مقاله انگلیسی نقش اسیدلوئیس در سنتز ایندول نیتزسکو به همراه ترجمه فارسی
عنوان فارسی مقاله: | نقش اسیدلوئیس در سنتز ایندول نیتزسکو |
عنوان انگلیسی مقاله: | The role of a Lewis acid in the Nenitzescu indole synthesis |
رشته های مرتبط: | شیمی، شیمی آلی، شیمی کاربردی، شیمی پلیمر، شیمی کاتالیست |
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کیفیت ترجمه | کیفیت ترجمه این مقاله پایین میباشد |
نشریه | الزویر – Elsevier |
کد محصول | f160 |
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بخشی از ترجمه فارسی مقاله: چکیده |
بخشی از مقاله انگلیسی: Abstract A highly efficient Lewis acid-catalyzed method for the Nenitzescu synthesis of 5-hydroxyindoles with a range of substituents at N-1 and C-3 and symmetric 5,50 -dihydroxydiindoles has been developed. The amount of the catalyst (10–100 mol %) required depended on the nature of the enaminone component. It has been shown that Lewis acid plays a role in enaminone component activation through an enamine-ZnC12 complex followed by its deprotonation. The Nenitzescu reaction has proven to be important in drug discovery for 5-hydroxyindole-based derivatives bearing new additional functions at various positions of the ring system.1-4 5-Hydroxyindoles with a high density of functional and pharmacophoric groups are of interest as novel inhibitors for protein targets.5 However, 3-acyl-5-hydroxyindoles, especially those with N-functionalized alkyl tails, and symmetric 5,50 -dihydroxydiindoles bearing a linker between the indole nitrogens, are not easily attainable due to formation of the corresponding 3-acylbenzofurans instead of the target indoles.6 The use of diketodienamines derived from acetyl acetone and ethylene- or butylenediamines in the Nenitzescu reaction in acetic acid has been reported to afford 3-acetyl-5-hydroxy-2-methyl-benzofuran/naphthofuran, instead of symmetric 5,50 -dihydroxydiindoles.7 Earlier, Grinev managed to obtain 3-acetyl-5-hydroxy-1-(2-hydroxyethyl)-2-methylindole in very low yield along with 3-acetyl-5-hydroxy-2-methylbenzofuran.8 We reasoned that employing Lewis acids in the Nenitzescu reaction with enaminones would direct the process to the indolization pathway.9 The method is simple, rapid, efficient, and allows the preparation of hydroxyindoles from p-benzoquinone (PBQ) and simple enaminones in good to excellent yields with the use of low polarity solvents in the presence of weak Lewis acid catalysts (hereafter referred to as ‘standard conditions’). The time required for the indolization decreases by a factor of three or more, compared to the non-catalyzed process, while the formation of 3-acylbenzofurans is supressed. The formation of 5-hydroxyindoles under such mild conditions is explained in terms of a non-redox mechanism. It was noted that the corresponding 5-hydroxybenzofurans were obtained by the condensation of PBQ with acetyl acetone or ethyl acetoacetate in the presence of Lewis acid catalysts.10 We chose a series of enaminones 1-5 with the structural unit Z–N–C@C–COR (Z = (CH2)3CH3 1, (CH2)2NHTs, 2, (CH2)2OH 3, (CH2)nNHC(CH3)@CHCOR 4 (n = 2), 5 (n = 6); R = Me, OEt, Ph) (Schemes 1 and 2). Under standard conditions (10 mol % ZnCl2/ CH2Cl2 system and PBQ (1 equiv)), the method9 worked well only with enaminone 2a of enaminones 1–3a to give pure indole 7a11 in 88% isolated yield (Table 1, entries 1, 5 and 7). Moreover, 2a reacted with PBQ faster than did the enaminone 3a and other simple enaminones.9 Similarly, enaminones 2b,c reacted smoothly under the same conditions to give indoles 7b,c in high yields (Table 2). |