Ionic Liquid from Vitamin B1 Analogue and Heteropolyacid: A Recyclable Heterogeneous Catalyst for Dehydrative Coupling in Organic Carbonate

The ionic liquid [HMTH] 2 H 2 [SiW 12 O 40 ] was prepared from the inexpensive, nontoxic vitamin B1-like compound, i.e., 5-(2-hydroxyethyl)-4-methylthiazole (HMT), and the noncorrosive heteropolyacid (H 4 SiW 12 O 40 ). This acidic ionic liquid was found to be an efficient heterogeneous catalyst for the direct dehydrative coupling of alcohols with alcohols (or alkenes) to synthesize various polysubstituted olefins in good to excellent yields with dimethyl carbonate (DMC) as a green solvent. Furthermore, this protocol was applicable in a gram-scale reaction, and the catalyst could be used at least for 8 runs without significant loss of activity.