Zinc Mediated Friedel-Crafts Acylation in Solvent-Free Conditions under Microwave Irradiation
Satya Paul, Puja Nanda, Rajive Gupta*, André Loupy
*Department of Chemistry, University of Jammu, Jammu-180 006, India, Email:
rajgupta
sancharnet.in
S. Paul, P. Nanda, R. Gupta, A. Loupy, Synthesis, 2003, 2877-2881.
DOI: 10.1055/s-2003-42485
Abstract
Zn powder catalyzes the Friedel-Crafts acylation of aromatic compounds with acyl halides efficiently under microwave irradiation in solvent-free conditions. Activated substrates undergo acylation predominantly at the para-position. The Zn powder can be re-used up to six times after simple washing with diethyl ether and dilute HCl.
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Details
The document discusses a novel method for Friedel–Crafts acylation of aromatic compounds using zinc powder as a catalyst under microwave irradiation in solvent-free conditions. This method offers a green and efficient alternative to traditional methods that use toxic catalysts like anhydrous AlCl3, which generate significant waste and are difficult to recycle. Zinc powder, being non-toxic and inexpensive, can be reused up to six times after simple washing with diethyl ether and dilute HCl, making the process more economical and environmentally friendly.
The study highlights that microwave irradiation significantly accelerates the reaction, achieving high yields of acylated products in short times compared to conventional heating methods. The reactions predominantly yield para-substituted products, and the method has been successfully applied to various aromatic substrates, including benzene, toluene, and anisole, among others.
Experimental conditions such as the ratio of zinc powder to substrate, irradiation time, and microwave power level were optimized to ensure maximum efficiency and safety. The document also compares the results of microwave-assisted reactions with those conducted under thermal conditions, demonstrating the superior efficiency of microwave irradiation.
Overall, this method provides a simple, rapid, and environmentally benign approach to Friedel–Crafts acylation, with high product yields and minimal waste.
Selective Fries Rearrangement Catalyzed by Zinc Powder
S. Paul, M. Gupta, Synthesis, 2004, 1789-1792.
Key Words
Friedel-Crafts Acylation, zinc powder,aromatic compounds, solvent-free conditions, microwave synthesis
ID: J66-Y2003-2160
