Superacid Resin‐Based Heterogeneous Catalysts for the Selective Acylation of 1,2‐Methylenedioxybenzene
Nicola Schiaroli, Alessandro Allegri, Martina Eberle, Stefano Billi, Alberto Guerrini, Stefania Albonetti, Angelo Vaccari, Tommaso Tabanelli, Carlo Lucarelli
Abstract
Abstract In this work, we firstly report on the use of highly active and selective Aquivion superacid resins as heterogeneous catalysts for the acylation of 1,2‐methylenedioxybenzene (MDB) with propionic anhydride (AP). The reaction was investigated and optimized using solvent‐free conditions to selectively produce 3,4‐methylenedioxypropiophenone (MDP1P), a key intermediate for the manufacture of active ingredients used in insecticide formulations with a volume of production of roughly 3000 t/y. Interestingly, Aquivion‐based catalysts allows to work in mild reaction conditions (i. e. 80 °C), obtaining MDP1P yields as high as 44 % after only 1 h of reaction (selectivity 83 %). A detailed study of the AP reactivity demonstrated its tendency to promote oligomerization reactions that, as confirmed by ex‐situ and in‐situ FT‐ATR analyses, caused the deactivation of the catalyst forming surficial carbonaceous residues. In this context, a fast oxidation of the resin surface organic residues using a diluted HNO 3 (or H 2 O 2 ) solution was proven to be an efficient method to regenerate the catalyst, which can be reused for several reaction cycles. The results obtained in preliminary scale‐up tests were basically unaffected by the reaction volume (up to 800 mL), paving the way for possible future applications of the process.