Vapour phase reaction of m-cresol and ethyl acetate over MCM-41 molecular sieves: One-pot synthesis of coumarin derivatives

Mesoporous Al-MCM-41 (Si/Al = 55 and 104) and Al,Zn-MCM-41 (Si/(Al + Zn) = 102) were synthesized by the surfactant-templated route. The catalytic activity was evaluated in the vapour phase reaction of m-cresol with ethyl acetate in the temperature range 200–400 °C. The identified products were 4,7-dimethylcoumarin (4,7-DMC), 2-acetyl-5-methylphenol (2A-5MP), 3-methylphenyl acetate (3-MPA), 2-ethyl-5-methylphenol (2E-5MP) and 4-ethyl-3-methylphenol (4E-3MP). Reaction parameters such as temperature, feed ratio and WHSV were optimised to obtain high 4,7-DMC selectivity at maximum conversion of m-cresol. The time-on-stream study revealed slow deactivation of the catalyst under optimum conditions. Though alkylation of m-cresol was the reaction, acylation dominated over alkylation, suggesting that ethyl acetate is also an active acylating agent for m-cresol. Ring acylation followed by esterification, and subsequent intramolecular condensation observed in this study, suggest an interesting novel one-pot route for the synthesis of coumarin derivatives in the vapour phase.