Efficient Production and Isolation of 3-Acetamido-5-Acetylfuran from N-Acetyl-D-Glucosamine within Protic Ionic Liquids.

Abstract

The transformation of chitin and its monomer N-acetylglucosamine (NAG) to high-value organonitrogen chemicals has attracted increasing interest, with 3-acetamido-5-acetylfuran (3A5AF) proposed as a versatile platform chemical. The preparation of 3A5AF from NAG has relied on high boiling organic solvents, ionic liquids (ILs) or deep eutectic solvents (DES). While these methods have met with some success, the isolation of 3A5AF and recycling of the solvent remains problematic for non-IL methods whereas most IL methods utilize inherently expensive aprotic ILs with substantial environmental footprints. This study details the preparation of 3A5AF in more cost-effective chloride-based protic ILs (PILs) with lower synthetic footprints than conventional ILs. Maximum yields of 42.5 %, 51.5 % and 57.0 % of 3A5AF were afforded in 1,8-diazabicyclo[5.4.0]undec-7-ene chloride ([DBU]Cl), tripropylammonium chloride ([TPA]Cl) and tributylammonium chloride ([TBA]Cl) respectively with 2 eq. B(OH)₃ at 150 °C. The 3A5AF formed was readily isolated by simple solvent extraction, avoiding column chromatography, with selected systems displaying good recyclability and scalability. E-factor calculations revealed that the PIL methodology produced substantially less waste than approaches for the production of 3A5AF from molecular solvents and DES, highlighting that PILs are suitable solvents for the sustainable production of 3A5AF.