Hexane-1,2,5,6-tetrol as a Versatile and Biobased Building Block for the Synthesis of Sustainable (Chiral) Crystalline Mesoporous Polyboronates

Abstract

We report on the synthesis and characterization of novel mesoporous chiral polyboronates obtained by condensation of ( R , S )/( S , S )-hexane-1,2,5,6-tetrol (HT) with simple aromatic diboronic acids (e.g., 1,3-benzenediboronic acid) (BDB). HT is a cellulose-derived building block comprising two 1,2-diol structures linked by a flexible ethane bridge. It typically consists of two diastereomers one of which [( S , R )-HT] can be made chirally pure. Boronic acids are abundantly available due to their importance in Suzuki–Miyaura coupling reactions. They are generally considered nontoxic and easy to synthesize. Reactive dissolution of generally sparingly soluble HT with BDB, in only a small amount of solvent, yields the mesoporous HT/polyboronate materials by spontaneous precipitation from the reaction mixture. The 3D nature of HT/polyboronate materials results from the entanglement of individual 1D polymeric chains. The obtained BET surface areas (SAs) and pore volumes (PVs) depend strongly on HT’s diastereomeric excess and the meta/para orientation of the boronic acids on the phenyl ring. This suggests a strong influence of the curvature(s) of the 1D polymeric chains on the final materials’ properties. Maximum SA and PV values are respectively 90 m 2 g –1 and 0.44 mL g –1 . Variably sized mesopores, spanning mainly the 5–50 nm range, are evidenced. The obtained pore volumes rival the ones of some covalent organic frameworks (COFs), yet they are obtained in a less expensive and more benign fashion. Moreover, currently no COFs have been reported with pore diameters in excess of 5 nm. In addition, chiral boron-based COFs have presently not been reported. Scanning electron microscopy reveals the presence of micrometer-sized particles, consisting of aggregates of plates, forming channels and cell-like structures. X-ray diffraction shows the crystalline nature of the material, which depends on the nature of the aromatic diboronic acids and, in the specific case of 1,4-benzenediboronic acid, also on the applied diastereomeric excess in HT.

Mechanistic Insights into the Conversion of Biorenewable Levoglucosanol to Dideoxysugars

“…The tetrol diastereomer ratio, determined by the starting LGOL threo/erythro ratio and by which intermediates (DDM and DDG, or DDF) are formed during the reaction, is an important property as it could influence the physical–chemical properties of tetrol-derived materials . For example, recently, De bruyn et al demonstrated that the diastereomeric excess of tetrol affected the surface areas and the porosities of the resulting chiral porous polyboronates obtained by reaction of tetrol and aromatic boronic acids.…”

Production of Hexane-1,2,5,6-tetrol from Biorenewable Levoglucosanol over Pt-WOx/TiO2

“…Channeling the production of commodity chemicals from petroleum-derived resources to renewable lignocellulosic feedstocks is a great route to the effective transitioning of the chemical industry toward materials and products with a lower CO 2 footprint. Biomass-derived monomers can be used as important platform molecules for the synthesis of polymers, resins, solvents, surfactants, among others. − Sugar derivatives have been shown to offer many opportunities to obtain such platform molecules. , Levoglucosenone (LGO) is a biobased sugar-like compound, which can be produced from cellulose by mild pyrolysis. − Notably, based on the pyrolytic method developed by the Circa Group, an actual 1000 ton LGO/year plant is currently being developed in France . LGO can also be produced at yields up to 51% using polar aprotic solvents and sulfuric acid at 170–230 °C .…”

“…Our group has recently demonstrated how Lgol can be selectively converted into tetrol . Tetrol is a polyol of industrial interest, ,, which could be potentially useful to the synthesis of a range of polymers. , Also, since the molecule displays two chiral centers, it can have potential uses as a chiral synthon . Tetrol is obtained by the selective C–O cleavage of the anhydrobridge of Lgol in water over a Brønsted acid catalyst, forming the dideoxy sugar intermediates 3,4-dideoxymannose (DDM) from t-Lgol and 3,4-dideoxyglucose (DDG) from e-Lgol.…”

Synthesis of Hexane-Tetrols and -Triols with Fixed Hydroxyl Group Positions and Stereochemistry from Methyl Glycosides over Supported Metal Catalysts

“…Hydrolysis of levoglucosanol forms 3,4-dideoxy sugar intermediates that are then hydrogenated to a mixture of (2 R ,5 S )-1256-HTet and (2 S ,5 S )-1256-HTet. De bruyn and co-workers synthesized chiral mesoporous polyboronates from 1256-HTet, showing that the stereochemistry of 1256-HTet influences the porosity properties of these materials …”

“…De bruyn and co-workers synthesized chiral mesoporous polyboronates from 1256-HTet, showing that the stereochemistry of 1256-HTet influences the porosity properties of these materials. 27 Polyol-based nonionic surfactants, comprised of a hydrophilic polyol head group and hydrophobic tail, have gained attention for cosmetics and pharmaceuticals applications because of their biodegradability and nontoxicity. Key properties, such as hydrophilicity and phase behavior, are a strong function of the number, positions, and stereochemistry of hydroxyl groups.…”