Aqueous olefin metathesis with ᴅ-glucose-based bromides giving more efficient catalysis

Abstract

Ring-closing metathesis of a model substrate, diethyl diallylmalonate, was used to study a new catalytic system based on the commercially available HG2 catalyst and ionic liquids derived from ᴅ-glucose employed as surfactants in an aqueous metathesis reaction. The quantity, structure, and concentration of ᴅ-glucose-based bromides were optimized to obtain high product yield and purity. (N-[2-(β-ᴅ-glucopyranosyloxy)ethyl]-N,N-dimethyl-N-dodecyl-ammonium bromide) was the most active surfactant, with a critical micelle concentration of 0.020 mol/dm3. HG2 was used in truly catalytic amounts (0.2 mol%) at 25 °C, enabling the synthesis of product in 180 min. High conversion (88%) and selectivity (100%), with low Ru content in the product, were obtained. Five cycles of a model metathesis reaction could be conducted without the loss of surfactant activity and with low Ru content in the product. 1H NMR spectroscopic studies showed the formation of micelles and the transformation of the substrate, in the presence of the catalyst, to product.