Going Beyond the Limits of the Biorenewable Platform: Sodium Dithionite-Promoted Stabilization of 5-Hydroxymethylfurfural

Biobased 2,5-Bis(hydroxymethyl)furan as a Versatile Building Block for Sustainable Polymeric Materials

Furanic polymers, currently mainly represented by polyethylene 2,5-furandicarboxylate (PEF), also known as polyethylene furanoate, have a fantastic potential to replace fossil-based polymers: for example, polyethylene terephthalate (PET). While 2,5-furandicarboxylic acid (FDCA), a precursor of PEF, and its derived polymers have been studied extensively, 2,5-bis(hydroxymethyl)furan (BHMF) has received relatively little attention so far. Similarly to FDCA, BHMF is a biobased platform chemical derived from renewable sources such as sugars. This review highlights different polymerization techniques for BHMF-based polyesters and addresses BHMF's relative instability during the synthesis of BHMF-derived polymers, including polycarbonates and polyurethanes. Furthermore, the degradability of furanic polyesters is discussed and BHMF's toxicity is briefly elaborated.

Tandem Thio-Michael Addition/Remote Lactone Activation of 5-Hydroxymethylfurfural-Derived δ-Lactone-Fused Cyclopentenones

The creation of structurally diverse chemical entities from fairly simple biorefinery products remains a challenge. In this work 5-hydroxymethylfurfural (HMF) was identified as a key synthon for preparing highly complex cyclopentenones (CP) via tandem 1,4-addition/elimination/remote lactone activation to external O- and N-nucleophiles in δ-lactone-fused-CPs hotspots. This scaffold was also reactive enough to be incorporated into model cysteine-peptides in low concentrations, paving the way to a potential translation generating complexity in the synthesis of small peptides. The new enones also exhibited activity against intraerythrocytic Plasmodium falciparum (IC₅₀ =1.32 μm).

Preparation of Thioaminals in Water

The presence of sulfur–carbon bonds is transversal to several areas of chemistry, e.g., drug discovery, materials, and chemical biology. However, a lack of efficient and sustainable procedures for the preparation of thioaminals, the N,S-analogues of O,O-acetals, contributes to this functional group often being overlooked by the scientific community. In this work is described the formation of thioaminals in water promoted by copper(II) triflate.

Efficient Piancatelli rearrangement on a large scale using the Zippertex technology under subcritical water conditions

A series of furyl carbinols, which were directly obtained from a bio-sourced raw material, were efficiently transformed into cyclopentenone derivatives in good yields and on a large scale using the Zippertex technology under subcritical water conditions.

Synthetic approaches to 2,5-bis(hydroxymethyl)furan (BHMF): a stable bio-based diol

Biorefinery is defined as a sustainable process where biomass is converted in a spectrum of marketable products and fuels. In this view, C6 furan-based compounds, usually referred as furanics, have been extensively investigated as aromatic promising building blocks from renewables. 5-Hydroxymethylfurfural (HMF) and 2,5-furan dicarboxylic acid (FDCA) are well known examples of furanics whose syntheses and applications have been extensively reviewed in the literature. Herein for the first time it is reported a comprehensive overview on the synthetic procedures to another bio-derived furan compounds, i.e. 2,5-bis(hydroxymethyl)furan (BHMF), a stable bio-based diol with numerous applications as monomer for bio-materials and fuels. Advantages and limitations of the different synthetic approaches are addressed, as well as possible future developments to render this compound part of the biorefinery market.

The Increasing Value of Biomass: Moving From C6 Carbohydrates to Multifunctionalized Building Blocks via 5-(hydroxymethyl)furfural

Recent decades have been marked by enormous progress in the field of synthesis and chemistry of 5-(hydroxymethyl)furfural (HMF), an important platform chemical widely recognized as the "sleeping giant" of sustainable chemistry. This multifunctional furanic compound is viewed as a strong link for the transition from the current fossil-based industry to a sustainable one. However, the low chemical stability of HMF significantly undermines its synthetic potential. A possible solution to this problem is synthetic diversification of HMF by modifying it into more stable multifunctional building blocks for further synthetic purposes.

Controlling the Reaction Networks for Efficient Conversion of Glucose into 5-Hydroxymethylfurfural

Biomass-derived hexose constitutes the main component of lignocellulosic biomass for producing value-added chemicals and biofuels. However, the reaction network of hexose is complicated, which makes the highly selective synthesis of one particular product challenging in biorefinery. This Review focuses on the selective production of 5-hydroxymethylfurfural (HMF) from glucose on account of its potential significance as an important platform molecule. The complex reaction network involved in glucose-to-HMF transformations is briefly summarized. Special emphasis is placed on analyzing the complexities of feedstocks, intermediates, (side-) products, catalysts, solvents, and their impacts on the reaction network. The strategies and representative examples for adjusting the reaction pathway toward HMF by developing multifunctional catalysts and promoters, taking advantage of solvent effects and process intensification, and synergizing all measures are comprehensively discussed. An outlook is provided to highlight the challenges and opportunities faced in this promising field. It is expected to provide guidance to design practical catalytic processes for advancing HMF biorefinery.

Current Situation of the Challenging Scale-Up Development of Hydroxymethylfurfural Production

Hydroxymethylfurfural (HMF) is a high-value platform chemical derived from renewable resources. In recent years, considerable efforts have been made to produce HMF also at industrial scale, which still faces some challenges regarding yield as well as sustainable and economic process designs. This critical Review evaluates the industrial process development of sustainable biomass conversion to HMF. Qualitative and quantitative guidelines are defined for the technological assessment of the processes described in patent literature. The formation of side products, difficulties in the separation and purification of HMF as well as catalyst regeneration were identified as major challenges in the HMF production. A first small-scale, commercial HMF production plant with a capacity of 300 tHMF per year has been operating in Switzerland since 2014.

Creating Diversity from Biomass: A Tandem Bio/Metal-Catalysis towards Chemoselective Synthesis of Densely Substituted Furans

A new chemoselective (enzymatic desymmetrization/Ru-catalyzed C-H activation) sequence to obtain differently substituted furans from the largely available 2,5-furandicarboxylic acid (FDCA) was developed. Series of di- and trisubstituted furans were prepared in very good yields and excellent chemoselectivity. This study discloses a new approach towards valorization of the furanics platform through the use of FDCA as a stable intermediate, thus circumventing the chemical instability of the parent 5-hydroxymethylfurfural.

Solvent issues in the Baylis-Hillman reaction of 5-hydroxymethyl furfural (HMF) and 5-glucosyloxymethyl furfural (GMF). Towards no-solvent conditions

The possibility to apply solventless conditions for the Baylis-Hillman reaction of 5-hydroxymethyl furfural (HMF) and its glucosylated analog, glucosyloxymethyl furfural (GMF) has been investigated. This study shows that highly functionalized adducts can be obtained in fair to good yields, under the conditions combining the renewability of the substrates, the straightforwardness of the strategy, and the lowered cost and toxicity of the solvent conditions. The issue of the polarity of the furanic substrate is addressed by comparing HMF with furfural and GMF.

When Will 5-Hydroxymethylfurfural, the "Sleeping Giant" of Sustainable Chemistry, Awaken?

Bring on the subs! Biorefining will be realized by using two different approaches: the production of new biobased molecular targets or sustainable access to traditional base and commodity chemicals. Awakening of 5-hydroxymethylfurfural (HMF) can be expected with different probabilities, depending on the approach chosen to create a sustainable future.

5-Hydroxymethylfurfural (HMF) in Organic Synthesis: A Review of its Recent Applications Towards Fine Chemicals

Background:

5-Hydroxymethylfurfural (5-HMF) is a biomass-derived platform chemical, which can be produced from carbohydrates. In the past decades, 5- HMF has received tremendous attention because of its wide applications in the production of various value-added chemicals, materials and biofuels. The manufacture and the catalytic conversion of 5-HMF to simple industrially-important bulk chemicals have been well reviewed. However, employing 5-HMF as a building block in organic synthesis has never been summarized exclusively, despite the rapid development in this area.

Objective:

The aim of this review is to bring a fresh perspective on the use of 5-HMF in organic synthesis, to the exclusion of already well documented conversion of 5-HMF towards relatively simple molecules such as 2,5-furandicarboxylic acid, 2,5-dimethylfuran and so on notably used as monomers or biofuels.

Conclusion:

As it has been shown throughout this review, 5-HMF has been the object of numerous studies on its use in fine chemical synthesis. Thanks to the presence of different functional groups on this platform chemical, it proved to be an excellent starting material for the preparation of various fine chemicals. The use of this C-6 synthon in novel synthetic routes is appealing, as it allows the incorporation of renewable carbonsources into the final targets.

Direct Conversion of Activated 5-Hydroxymethylfurfural into δ-Lactone-Fused Cyclopentenones

Valorization of biomass derived feedstock (e.g., 5-hydroxymethylfurfural platform) is a very active field of chemical research. In this study, 5-hydroxymethylfurfural is converted into cyclopenten-2-ones by virtue of furfural's activation and Meldrum's acid's tendency to undergo decomposition/esterification. Experimental and computational studies suggest a domino rearrangement-lactonization reaction involving BINOL-catalyzed lactonization as the rate-determining step. The novel lactone-fused cyclopenten-2-ones, which bear a quaternary carbon and resemble a didemnenone natural product structure, are converted into several derivatives with potential interest for the fields of synthetic and medicinal chemistry.

Towards Improved Biorefinery Technologies: 5-Methylfurfural as a Versatile C6 Platform for Biofuels Development

Low chemical stability and high oxygen content limit utilization of the bio-based platform chemical 5-(hydroxymethyl)furfural (HMF) in biofuels development. In this work, Lewis-acid-catalyzed conversion of renewable 6-deoxy sugars leading to formation of more stable 5-methylfurfural (MF) is carried out with high selectivity. Besides its higher stability, MF is a deoxygenated analogue of HMF with increased C/O ratio. A highly selective synthesis of the innovative liquid biofuel 2,5-dimethylfuran starting from MF under mild conditions is described. The superior synthetic utility of MF against HMF in benzoin and aldol condensation reactions leading to long-chain alkane precursors is demonstrated.