(574a) Production of Terephthalate Esters Via Diels-Alder Cycloaddition-Dehydration Reactions of 1,2-Furandicarboxylate Esters and Ethylene

 Diels-Alder cycloaddition-dehydration (DA) reactions of dienophiles and biomass-derived furans are promising routes to renewable aromatics. Catalysis of such reactions with ethylene as the dienophile has been the topic of numerous experimental and computational studies. DA reactions of furans with reduced side groups (e.g., dimethyl furan) have been shown to be catalyzed with high selectivity by microporous materials with Brønsted or Lewis acid sites.¹ However, furans functionalized with oxygenated side groups (e.g., partially oxidized products of 5-hydroxymethyl furfural) were shown to be more prone to side-reactions.^2,3 For these reations, Lewis acidic Sn- or Zr-containing molecular sieves with the zeolite beta topology were found to be more selective catalysts than the Brønsted acidic Al-Beta. Zr-Beta yielded the highest selectivities (ca. 80%), with methyl (5-methoxymethyl) furan-2-carboxylate (MMFC) as the diene. However, the further oxidized 1,2-furandicarboxylic acid (FDCA), or esters thereof, were shown to be unreactive with such catalysts.

Recently, we have reported on the synthesis and characterization of Zn Lewis acid sites in CIT-6 (Zn-Beta).^4 We showed that, in addition to enabling DA reactions of MMFC, CIT-6 is able to react the dimethyl ester of FDCA (DMFDC). However, in the latter case, catalysis of decarboxylation reactions of the furan compromised selectivity towards the diester aromatic products, with the highest selectivity of 36%.

Here, we report a set of microporous catalysts for such DA reactions that do not appear to promote decarboxylation of DMFDC, and the optimization of reaction conditions that enables terephthalate diester selectivities upwards of 88%.

References:

(1) Chang, C.-C.; Je Cho, H.; Yu, J.; Gorte, R. J.; Gulbinski, J.; Dauenhauer, P.; Fan, W. Green Chem. 2015.

(2) Pacheco, J. J.; Davis, M. E. Proc. Natl. Acad. Sci. U. S. A. 2014, 111(23), 8363â??8367.

(3) Pacheco, J. J. New Catalysts for the Renewable Production of Monomers for Bioplastics, PhD Dissertation, California Institute of Technology, 2015.

(4) Orazov, M.; Davis, M. E. Chem. Sci. 2016, 7(3), 2264â??2274.

*Corresponding author. E-mail: mdavis@cheme.caltech.edu