Catalytic Conversion of Sugar-Derived Polyhydroxy Acid to Trimellitate

Abstract

Biomass resources, especially carbohydrates derived from cellulose and hemicellulose, could be utilized as an alternative feedstock for the production of fuel and bulk chemicals. Here, we present a sustainable route for the synthesis of trimethyl trimellitate from 1,6-dimethyl galactarate, the diester of sugar-derived polyhydroxy galactaric acid. The process starts with the deoxydehydration reaction of 1,6-dimethyl galactarate to form dimethyl muconate with an 84% yield. Nuclear magnetic resonance (NMR) and density functional theory results show that the molecular structure of 1,6-dimethyl galactarate possesses strong intramolecular hydrogen bond networks and is endowed with chemical recalcitrance. ¹H NMR tests of variable catalyst concentrations reveal that the introduction of ammonium perrhenate could weaken the intramolecular hydrogen bond effect and activate the chemically inert molecules. The Diels–Alder reaction of muconate and acrylate is conducted efficiently to produce a substituted cyclohexene intermediate without any catalyst used, and a 72% yield of the target product, trimethyl trimellitate, is obtained via the dehydro-aromatization reaction of the cycloadduct. This new approach provides a template path for the synthesis of aromatic oxygenated compounds and would promote the development of green polymer materials.