Solvent free synthesis of 7-isopropyl-1,1-dimethyltetralin by the rearrangement of longifolene using nano-crystalline sulfated zirconia catalyst

• Published in: Journal of molecular catalysis. A, Chemical Vol. 301; no. 1; pp. 67 - 78
• Main Authors: Tyagi, Beena, Mishra, Manish K., Jasra, Raksh V.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 18.03.2009; Elsevier
• Subjects: 7-Isopropyl-1,1-dimethyltetralin; Catalysis; Chemistry; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Isolongifolene; Longifolene isomerization; Longifolene rearrangement; Nano-crystalline sulfated zirconia; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Isolongifolene; 7-Isopropyl-1,1-dimethyltetralin; Nano-crystalline sulfated zirconia; Longifolene rearrangement; Longifolene isomerization; Lewis acid; Binary compound; Lewis site; Catalyst selectivity; Isomerization; Acidic site; Transition element compounds; Acidity; Sulfates; Solid; Zirconia; Heterogeneous catalysis; Sol gel process; Solvent free reaction; 7-lsopropyl-1,1-dimethyltetralin; Kinetics; Sulfur; Catalyst; Nanocrystal; Modified material
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2008.11.011

Longifolene rearranges to 7-isopropyl-1,1-dimethyltetralin via isolongifolene over nano-crystalline sulfated zirconia (SZ) catalyst. ▪ Nano-crystalline sulfated zirconia solid acid catalyst, synthesized by a one-step sol–gel method, was studied for the rearrangement of longifolene to isolongifolene and 7-isopropyl-1,1-dimethyltetralin under solvent free conditions. Kinetic and 1H NMR spectroscopic studies confirmed the formation of 7-isopropyl-1,1-dimethyltetralin through further rearrangement of isolongifolene in the presence of a higher number of acidic sites. The selectivity for the rearranged products namely isolongifolene and 7-isopropyl-1,1-dimethyltetralin was observed to be strongly influenced by the acidity of the catalysts in terms of Brönsted (B) and Lewis (L) acid sites ratio. The catalyst having a higher B/L ratio (5.6) showed higher selectivity (56%) for 7-isopropyl-1,1-dimethyltetralin. The selectivity for the products could also be controlled by longifolene to catalyst weight ratio; for example, ∼100% isolongifolene could be obtained using less amount of the catalyst, whereas for 7-isopropyl-1,1-dimethyltetralin higher amount of catalyst was required. Thermally regenerated catalyst showed decreased selectivity for 7-isopropyl-1,1-dimethyltetralin due to a decrease in the B/L ratio, which in turns influenced by loss of sulfur during the reaction.