Synthesis of valuable benzenoid aromatics from bioderived feedstock

Abstract

Aromatic chemicals play indispensable roles in our daily lives, having broad applications in household goods, textiles, healthcare, electronics and automotive, but their production currently relies on fossil resources that have heavy environmental burdens. Synthesis of aromatic chemicals from bio-based resources would be a viable approach to improve their sustainability. However, very few methods are available for achieving this goal. Here we present a strategy to synthesize aromatics from 5-hydroxymethylfurfural (HMF), an organic compound derived from sugars under mild conditions. HMF was first converted in two high-yielding steps into 2,5-dioxohexanal (DOH), a novel C6-compound containing three carbonyl groups. Subsequently, acid-catalysed intramolecular aldol condensation of DOH in the presence of secondary amines selectively produced a range of bio-based 4-dialkylamino substituted phenols and 1,4-di-(dialkylamino)benzenes (Wurster’s blue analogues) in 15–88% yields. In the absence of amines, the industrially important hydroquinone was also synthesized from DOH under acidic conditions. Using a similar approach where 4,5-dioxohexanal was the intermediate, we were also able to prepare catechol, a compound with important industrial applications, from HMF. The proposed approach can pave the way for the production of sustainable aromatic chemicals and move their industrial applications closer to achieving a bioeconomy.