Yingying Luo, Aixia Pan, Min Xing
Jan 3, 2012
Citations
1
Influential Citations
11
Citations
Journal
Advanced Materials Research
Abstract
Acetylation of pyrene with acetyl chloride to 1-acetylpyrene catalyzed by chloroaluminate ionic liquids of different alkyl chain length and metal chloride was investigated. Pure 1-acetylpyrene was obtained and the structure of 1-acetylpyrene was identified by GC/MS, FT-IR and 1 HNMR spectra.[Emim]Cl/AlCl3([Emim] + =1-ethyl-3-met-hylimidazolium cation) ionic liquid was found to be the most active catalyst in the acylation. The yield of 1-acetylpyrene was up to 91.8% and the selectivity towards 1-acetylpyrene was up to 98.2%. The reusing experiment shows that [Emim]Cl-AlCl3 can be used as both catalyst and solvent, and it is reusable and environmentally friendly for the preparation of 1-acetylpyrene. Introduction Friedel-Crafts acylation of aromatic compounds is an ubiquitous reaction in the production of aromatic ketones,and largely used as intermediates in the synthesis of fine and speciality chemicals as well as pharmaceuticals. To date, acylations of benzene and naphthalene have been thoroughly investigated and widely used in the industry. 1-acetylpyrene is condensed with N-alkylated indole-3-carboxaldehydes to yield the ethylenic compounds, which are considered as significant drugs, since 1-acetylpyrene were examined for possible antiviral activity against HIV-1 using MT-4 cells astarget cells[1]. However, the current Friedel-Crafts acylation uses highly corrosive and potentially lethal acids, such as aluminium trichloride (AlCl3) and hydrofluoric acid (HF), both of which are not easily recovered with the release of environmentally unfriendly effluents. Furthermore, these Lewis acids are consumed in more than stoichiometric amounts due to the formation of 1:1 molar adduct with aromatic ketones and the subsequent separation of the product by hydrolysis, which is cumbersome, generates a large amount of hazardous, corrosive, environmentally unfriendly waste approximately more than 4 mol of Cl per mole of the ketone produced. The major drawback in this process is that the Lewis acid is non-regenerable[2]. In recent years, ionic liquids(ILs) have attracted increasing interest and been successfully used as environmentally benign catalysts and solvents in a variety of catalytic reactions due to their relatively low viscosities, low vapor pressure, high thermal, and chemical stability, etc[3-5]. Wilkes first reported the FriedelCrafts reactions of aromatic substrates, such as benzene, toluene, chlorobenzene, and nitrobenzene, in ILs[6]. To date, Friedel-Crafts acetylations of benzene, naphthalene, and their derivatives catalyzed by ILs have been given considerable attention. Acetylations of some polyaromatics, such as naphthalene, pyrene, phenanthrene and anthracene, in ILs were also investigated[7]. But the yield of 1-acetylpyrene reported was only 13% around[7]. In our laboratory, we have researched Friedel-Crafts acylation of anthracene, acenaphthene. Hence, in order to obtain the higher yield and selectivity of 1-acetylpyrene, we studied the catalytic properties of six kinds of Lewis acids. The effects of varying reaction conditions on the synthesis of 1-acetylpyrene in the selected ionic liquids were extensively studied. To the best of our knowledge, no acetylation of pyrene with acetyl chloride catalyzed by different ILs has been reported. Advanced Materials Research Online: 2012-01-03 ISSN: 1662-8985, Vols. 443-444, pp 917-922 doi:10.4028/www.scientific.net/AMR.443-444.917 © 2012 Trans Tech Publications Ltd, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific.net. (Semanticscholar.org-10/03/20,16:35:10) In the present paper, the catalytic activities of Lewis acidic ILs such as [Emim]Cl-AlCl3, [Bmim]Cl-AlCl3 and [Omim]Cl-AlCl3 ([Bmim] + =1-butyl-3-methylimidazolium cation, [Omim] + =1-octyl-3-methylimidazolium cation), in the acetylation of pyrene with acetyl chloride to 1-acetylpyrene(Scheme 1) were investigated under different experimental conditions. The Lewis acidic ILs were easily isolated from the products and effectively recycled.