Ecofriendly claisen rearrangement of allyl-4-tert-butylphenyl ether using heteropolyacid supported on hexagonal mesoporous silica

Abstract

The Claisen rearrangement of allyl phenyl ethers is a valuable reaction in organic synthesis having a variety of applications in perfumes, flavours, pharmaceuticals, and intermediate industries. The replacement of traditional environmentally threatening homogeneous acid catalysts in organic processes with solid acid catalysts is an important green chemistry goal. The Claisen rearrangement of allyl-4-tert-butylphenyl ether to 2-allyl-4-tert-butylphenol with 100% selectivity was accomplished in an efficient, economically and environmentally friendly route by employing the solid acid catalysts such as acid-treated clays, sulphated zirconia, 20% (w/w) dodecatungstophosphoric acid (DTP)/hexagonal mesoporous silica (HMS). 20% (w/w) DTP/HMS was found to be superior, reusable without loss of activity, and 100% selective towards 2-allyl-4-tert-butylphenol. Based on the experimental data a suitable mathematical model is proposed to describe the reaction kinetics. The results are novel.