Aliphatic aldehydes such as ethanal, propanal, n-butanal, isobutyraldehyde, n-valeraldehyde, isovaleraldehyde, n-hexanal and n-octanal were converted into the corresponding 2,4,6-trialkyl-1,3,5-trioxanes through cyclotrimerization in the presence of the ferric chloride based ionic liquids at room temperature without solvent in high selectivity. The effects of different ionic liquids, acidity of ionic liquids and temperature on cyclotrimerization were also studied. The results showed that the ferric chloride based ionic liquids (apparent molar fraction of FeCl 3 (x(FeCl 3 )＝ 0.62)) were a kind of efficient catalysts for the cyclotrimerization of aliphatic aldehyde which could be separated conveniently from the reaction mixture and recycled without loss of catalytic activity. The conversion of isobutyraldehyde and the selectivity to 2,4,6-triisopropyl-1,3,5-trioxane were 91.1% and 99.8% respectively under optimum reaction condition (isobutyraldehyde 25.0 g, [Et 3 NH]Cl/FeCl 3 (x(FeCl 3 )＝0.62) 1.0 g, 25 ℃ for 1 h) .

Acetalization of glycol with carbonyl compounds was carried out catalyzed by cupric p-toluenesulfonate. These carbonyl compounds included cyclohexanone, propionoaldehyde, n-butyraldehyde, iso-butyraldehyde, n-valeraldehyde, benzaldehyde and butanone. Satisfactory results were obtained: the conversions of these carbonyl compounds were more than 90%, the selectivities were higher than 99.1%, only 0.1% mole ratio of catalyst to substrate and 90 min were sufficient in most cases. The catalyst and products were separated easily by phase separation.

Other 6-membered heterocycles R 0670 Cyclotrimerization of Aliphatic Aldehydes Catalyzed by Ionic Liquids. -A new method for the synthesis of trialkyl trioxane derivatives is presented. Best results are achieved using FeCl3-based ionic liquid as catalyst which can be recovered easily and reused without loss of activity. -(YU, X.-Y.; LIU, C.-H.; YANG, J.-G.; HE*, M.-Y.; Chin.