“…In this regard, various catalysts have been recently reported to effect this reaction as indium triiodide [23], diphenylammonium triflate [24], amberlyst-15 [25] yttria-zirconia [26] Mo-ZrO 2 [27], lithium perchlorate [28], polymer-supported lipase [29], envirocat EPZG [30], hydrotalcite [31], clays [32] and zeolites [33]. Some of these catalysts are difficult to prepare and toxic.…”