Acylation of aromatic compounds by acid anhydrides using Preyssler's anion [NaP5W30O110]14- and heteropolyacids as green catalysts

Ali Gharib,Manouchehr Jahangir,J Scheeren

doi:10.2478/v10026-011-0017-6

Abstract

Acylation of aromatic compounds by acid anhydrides using Preyssler's anion [NaP5W30O110]14- and heteropolyacids as green catalysts The Preyssler, Wells-Dowson and Keggin heteropolyacids are efficient and eco-friendly solid acid catalysts for the acylation of electron-rich aromatic compounds with acid anhydrides. The performance of different forms of heteropolyacids was compared. In all the cases, the best results were obtained using the Preyssler heteropolyacid as the catalyst. In the presence of 25 mol% (with respect to H+ equivalency) Preyssler catalyst, highly para-selective acetylation of anisole occurs using two equivalents of acetic anhydride, in 15 min at room temperature. The isolated yield of the p-methoxyacetophenone product is 98%.

Highlights

Acylation of aromatic compounds is a widely used reaction for the production of fine chemicals[1]
Acylation of methoxybenzene with acetic anhydride The performance of this polyanion in different forms was compared with the Keggin-type catalysts H4[SiMo12O40], H4[SiW12O40], H3[PW12O40] and H3[PMo12O40]
The results showed the shape selective characteristic of heteropolyacids catalysts towards para isomer rather than other isomers due to its smaller molecular sizes compared to its counterpart ortho or meta isomers

Summary

INTRODUCTION

Acylation of aromatic compounds is a widely used reaction for the production of fine chemicals[1]. Considerable effort has been made to develop solid acid catalysts such as zeolites, clays, Nafion H2, and silica sulfuric acid[3] as heterogeneous catalysts of FriedelCrafts acylation[4]. We find that Preyssler's anion is a green and recyclable catalyst, and is a more effective catalyst than sulfuric acid when used in an organic solvent at different reaction temperatures. Under both homogeneous and heterogeneous catalysis, the results show that the performance of this catalyst is excellent. All of the different forms of this catalyst are recovered, and recycled with retention of their initial structure and activity

EXPERIMENTAL SECTION

Catalyst Preparation

RESULTS AND DISCUSSION

LITERATURE CITED