Atom-Economical Selective-Ring-Opening Reaction of Glycidol with 1-Naphthol Catalyzed by Magnesium Silicate of a Biogenic Silica Source

Abstract

Ring-opening reaction is one of the most important processes in organic transformations wherein selectivity of the desired product is dependent on a number of parameters. Selective ring opening of glycidol with 1-naphthol was studied to make propanolol glycol [or 3-(1-naphthyloxy)propane-1,2-diol] over magnesium silicate as a heterogeneous catalyst. Propanolol glycol is used in the treatment of hypertension. Magnesium silicate catalyst was produced by combusting a biogenic silica source material such as rice hulls to give rich hull ash (RHA), and it was characterized by using several techniques such as X-ray diffraction, scanning electron microscopy, temperature-programmed desorption, and Brunauer–Emmett–Teller N2 adsorption. The catalyst was highly active in ring-opening reaction, and 3-(1-naphthyloxy)propane-1,2-diol was the only product. The reaction was 100% atom selective. The effects of different kinetic parameters on the rate of ring opening of glycidol with 1-naphthol were studied systematically to establish the kinetics of the reaction. Magnesium silicate derived from RHA exhibited better catalytic behavior in the production of propanolol glycol with conversions of up to 80% in 3 h with 90% selectivity. The catalyst was characterized after the reaction and found to be robust without any loss of activity.