Synthesis of Ionones by Cyclization of Pseudoionone on Solid Acid Catalysts

Abstract

Ionone synthesis (α, β and γ isomers) by pseudoionone cyclization was studied on zeolite HBEA, Amberlyst 35W, SiO₂–Al₂O₃, and unsupported and silica-supported heteropolyacids (HPA/SiO₂). Ionone formation was preferentially promoted on strong Brønsted acid sites. A 79% ionone yield was obtained on 58.5 wt.% HPA/SiO₂ after 1.5 h of reaction at 383 K and 250 kPa. This value is similar to the best yields reported for the homogeneously-catalyzed reaction using sulfuric acid.