Improving the efficiency of the Diels-Alder process by using flow chemistry and zeolite catalysisElectronic supplementary information (ESI) available. See DOI: 10.1039/c6gc02334g

• Main Authors: Seghers, S, Protasova, L, Mullens, S, Thybaut, J. W, Stevens, C. V
• Format: Article
• Language: English
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/c6gc02334g

The industrial application of the Diels-Alder reaction for the atom-efficient synthesis of (hetero)cyclic compounds constitutes an important challenge. Safety and purity concerns, related to the instability of the polymerization prone diene and/or dienophile, limit the scalability of the production capacity of Diels-Alder products in a batch mode. To tackle these problems, the use of a high-pressure continuous microreactor process was considered. In order to increase the yields and the selectivity towards the endo -isomer, commercially available zeolites were used as a heterogeneous catalyst in a microscale packed bed reactor. As a result, a high conversion (≥95%) and endo -selectivity (89 : 11) were reached for the reaction of cyclopentadiene and methyl acrylate, using a 1 : 1 stoichiometry. A throughput of 0.87 g h −1 during at least 7 h was reached, corresponding to a 3.5 times higher catalytic productivity and a 14 times higher production of Diels-Alder adducts in comparison to the heterogeneous lab-scale batch process. Catalyst deactivation was hardly observed within this time frame. Moreover, complete regeneration of the zeolite was demonstrated using a straightforward calcination procedure. The industrial application of the Diels-Alder reaction for the synthesis of (hetero)cyclic compounds constitutes an important challenge. To tackle the reagent instability problems and corresponding safety issues, the use of a high-pressure and zeolite catalysed microreactor process is presented.