Selective Claisen rearrangement of allyl-2,4-di-tert-butylphenyl ether to 6-allyl-2,4-di-tert-butylphenol catalysed by heteropolyacid supported on hexagonal mesoporous silica

Abstract

The Claisen rearrangement of allyl phenyl ethers results into valuable products for fragrance, flavours, food, pharmaceuticals and intermediate industries and is typically initiated by using very high temperatures, normally beyond 200 °C. Homogeneous acid catalysts are also used for this rearrangement, which could be replaced profitably by using eco-friendly solid acids. The Claisen rearrangement of allyl-2,4-di-tert-butylphenyl ether to 6-allyl-2,4-di-tert-butylphenol was accomplished by employing the various solid acid catalysts such as K-10 clay, sulphated zirconia, 20% w/w dodecatungstophosphoric acid (DTP)/hexagonal mesoporous silica (HMS), and 20% w/w DTP/K-10. A 20% w/w DTP/HMS was found to be very active and also stable without any deactivation with 100% atom economy towards 6-allyl-2,4-di-tert-butylphenol, which is commercially a very valuable product. A systemic investigation of the effect of various operating parameters is done. Furthermore, a mathematical model is developed to describe the reaction kinetics, which is validated with experimental results. The results are novel.