One-step synthesis of methyl methacrylate from methyl propionate and methanol under mild condition

Abstract

In recent years, coal-based one-step synthesis of methyl methacrylate (MMA) stimulated researchers’ interest due to the over-capacity of coal chemical industry. However, the high reaction temperature, low yield and selectivity, catalyst deactivation due to carbon deposition, and volatilization and polymerization of formaldehyde have been the challenging problems in this field. In this work, the cascade reactions of methanol dehydrogenation to formaldehyde, aldol condensation between formaldehyde and methyl propionate, and O2-inteerrupted hydrogenation of MMA were resolved via construction of mild and efficient cobalt complex catalyzed interrupted hydrogen borrowing system. Thus, one-step synthesis of MMA from methyl propionate and methanol in liquid phase at 80 °C with yield and selectivity of 25.7% and 92.6% was realized. The cobalt complex activation and methanol dehydrogenation mechanisms were investigated with nuclear magnetic resonance (NMR) characterization, and the C–H bond activation and breakage of methanol was identified as the rate-controlling step through kinetic isotopic effect experiments, which provided new research direction for coal-based synthesis of MMA.