Benzoin condensation reactions of 5-membered heterocyclic compounds

Novel Riboflavin-Inspired Conjugated Bio-Organic Semiconductors

Flavins are known to be extremely versatile, thus enabling routes to innumerable modifications in order to obtain desired properties. Thus, in the present paper, the group of bio-inspired conjugated materials based on the alloxazine core is synthetized using two efficient novel synthetic approaches providing relatively high reaction yields. The comprehensive characterization of the materials, in order to evaluate the properties and application potential, has shown that the modification of the initial alloxazine core with aromatic substituents allows fine tuning of the optical bandgap, position of electronic orbitals, absorption and emission properties. Interestingly, the compounds possess multichromophoric behavior, which is assumed to be the results of an intramolecular proton transfer.

Recyclable montmorillonite-supported thiazolium ionic liquids for high-yielding and solvent-free upgrading of furfural and 5-hydroxymethylfurfural to C10 and C12 furoins

Six Na⁺/montmorillonite (MMT) – supported thiazolium (TM) ionic liquids (ILs) have been synthesized and employed to catalyze the highly selective condensation of furfural (FF) and 5-hydroxymethylfurfural (HMF) into C₁₀ and C₁₂ furoins, respectively.

Organocatalytic upgrading of furfural and 5-hydroxymethyl furfural to C10 and C12 furoins with quantitative yield and atom-efficiency

There is increasing interest in the upgrading of C₅ furfural (FF) and C₆ 5-hydroxymethyl furfural (HMF) into C₁₀ and C₁₂ furoins as higher energy-density intermediates for renewable chemicals, materials, and biofuels. This work utilizes the organocatalytic approach, using the in situ generated N,S-heterocyclic carbene catalyst derived from thiazolium ionic liquids (ILs), to achieve highly efficient self-coupling reactions of FF and HMF. Specifically, variations of the thiazolium IL structure have led to the most active and efficient catalyst system of the current series, which is derived from a new thiazolium IL carrying the electron-donating acetate group at the 5-ring position. For FF coupling by this IL (0.1 mol %, 60 °C, 1 h), when combined with Et₃N, furoin was obtained in >99% yield. A 97% yield of the C₁₂ furoin was also achieved from the HMF coupling by this catalyst system (10 mol % loading, 120 °C, 3 h). On the other hand, the thiazolium IL bearing the electron-withdrawing group at the 5-ring position is the least active and efficient catalyst. The mechanistic aspects of the coupling reaction by the thiazolium catalyst system have also been examined and a mechanism has been proposed.

Diesel and alkane fuels from biomass by organocatalysis and metal-acid tandem catalysis

Combo deal: Biomass furaldehydes are upgraded into oxygenated diesel and high-quality C10-12 linear alkane fuels. The first of two steps involves solvent-free self-condensation (Umpolung) through organocatalysis using an N-heterocyclic carbene (NHC), yielding C10 -C12 furoin intermediates. In the metal-acid tandem catalysis step, in water, the furoin intermediates are converted into oxygenated biodiesel by hydrogenation, etherification or esterification; or into premium alkane jet fuels by hydrodeoxygenation.