One-pot production of bio-based 2-methyltetrahydrofuran and 2,5-dimethyltetrahydrofuran: a review of heterogeneous catalytic approaches

The valorisation of biomass into value-added products plays an important role in the establishment of sustainable chemistry and a circular economy. Leveraged as renewable feedstocks, furfural (FF), 5-hydroxymethyl furfural (5-HMF), carbohydrates, and lignocellulose can be transformed into bio-based 2-methyltetrahydrofuran (2-MTHF) and 2,5-dimethyltetrahydrofuran (2,5-DMTHF) under specific conditions. This article presents a comprehensive discussion of the one-pot manufacture of renewable 2-MTHF and 2,5-DMTHF through the heterogeneous catalytic cascade of hydrodeoxygenation–hydrogenation and hydrodeoxygenation-transfer hydrogenation using H₂ and alcohols as green reductants. Particularly, this review provides a thorough understanding of catalyst design, reaction optimization, operation mode (batchwise vs. continuous flow), catalyst reusability, and mechanistic pathways to access the target products. Furthermore, an elaborate analysis of the outlook and constraints related to these straightforward and eco-friendly approaches is also presented.