Efficient Synthesis of 5‑(Hydroxymethyl)furfural Esters from Polymeric Carbohydrates Using 5‑(Chloromethyl)furfural as a Reactive Intermediate

Abstract

This work reports an efficient, gram-scale synthesis of 5-(hydroxymethyl)furfural (HMF) esters using biomass-derived 5-(chloromethyl)furfural (CMF) as a reactive intermediate. The HMF-esters have potential applications as chemical intermediates, fuel additives, and bioactive compounds. Initially, CMF was prepared in good yields directly from polymeric carbohydrates (starch, inulin, and cellulose) and cellulosic materials (cotton and filter paper) using a biphasic batch reaction system, consisting of aqueous hydrochloric acid and 1,2-dichloroethane. The use of ZnCl<inf>2</inf> as an additive allowed the reaction to proceed under milder conditions while significantly improving the isolated yield of CMF. The effects of reaction temperature, reaction time, extracting solvent, and ZnCl<inf>2</inf> loading on CMF yield were investigated. Microcrystalline cellulose was converted into CMF with a 72% isolated yield under optimized reaction conditions (80 °C, 2 h). After that, CMF was transformed into various novel esters of HMF in excellent isolated yields (>85%) by reacting with a slight excess amount of the triethylammonium salt of various alkyl/aryl carboxylic acids under solvent-free conditions. © 2022 American Chemical Society.