Cascade Reductive Etherification of Bioderived Aldehydes over Zr‐Based Catalysts

• Published in: ChemSusChem 2017-10, Vol.10 (20), p.4090-4101
• Main Authors: Shinde, Suhas, Rode, Chandrashekhar
• Format: Article
• Language: English
• Subjects: 2-Propanol - chemistry; Aldehydes; Aldehydes - chemistry; Aliphatic alcohols; Aliphatic compounds; biomass conversion; Carbon dioxide; cascade reactions; Catalysis; Catalysts; Charge transfer; Chemical synthesis; Ethers; Ethers - chemistry; Furaldehyde - analogs & derivatives; Furaldehyde - chemistry; heterogeneous catalysis; Hydrogenation; Hydroxymethylfurfural; Inductively coupled plasma; Models, Molecular; Molecular Conformation; Montmorillonite; Optical emission spectroscopy; Oxidation-Reduction; Spectrum analysis; Zirconium; Zirconium - chemistry
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201701275

An efficient one‐pot catalytic cascade sequence has been developed for the production of value‐added ethers from bioderived aldehydes. Etherification of 5‐(hydroxymethyl)furfural with different aliphatic alcohols over acidic Zr–montmorillonite (Zr‐Mont) catalyst produced a mixture of 5‐(alkoxymethyl)furfural and 2‐(dialkoxymethyl)‐5‐(alkoxymethyl)furan. The latter was selectively converted back into 5‐(alkoxymethyl)furfural by treating it with water over the same catalyst. The synthesis of 2,5‐bis(alkoxymethyl)furan was achieved through a cascade sequence involving etherification, transfer hydrogenation, and re‐etherification over a combination of acidic Zr‐Mont and the charge‐transfer hydrogenation catalyst [ZrO(OH)2]. This catalyst combination was further explored for the cascade conversion of 2‐furfuraldehyde into 2‐(alkoxymethyl)furan. The scope of this strategy was then extended for the reductive etherification of lignin‐derived arylaldehydes to obtain the respective benzyl ethers in >80 % yield. Additionally, the mixture of Zr‐Mont and ZrO(OH)2 does not undergo mutual destruction, which was proved by recycling experiments and XRD analysis. Both the catalysts were thoroughly characterized using BET, temperature‐programmed desorption of NH3 and CO2, pyridine‐FTIR, XRD, inductively coupled plasma optical emission spectroscopy, and X‐ray photoelectron spectroscopy techniques. Cheers, catalyst cocktail! A new cascade approach involving etherification, transfer hydrogenation, and etherification again over a combination of Zr‐Mont and ZrO(OH)2 catalysts was used for the synthesis of 2,5‐bis(alkoxymethyl)furan. The acidic character of Zr‐Mont facilitated etherification, whereas the acid–base characteristics of ZrO(OH)2 facilitated the transfer hydrogenation of the reaction intermediates to give the final ether product.