Nitrile Furanics via Copper‐Catalyzed Dehydration of Aldoximes and Knoevenagel Condensation

Nitrile furanic compounds have been prepared employing two simple synthetic approaches; i) dehydration of aldoximes and ii) Knoevenagel condensation. Both methodologies were firstly tested and optimized on furfural and thus exploited on 5-hydroxymethyl-2-furfural (HMF) and 5,5’-oxy(bismethylene)-2-furaldehyde (OBMF). All the resulting products were achieved in good to excellent yield and isolated as pure employing simple purification procedure.

Abstract

In this work two synthetic approaches to introduce nitrile moieties into bio-based derived furanic compounds were investigated, i. e., dehydration of aldoximes and Knoevenagel condensation. Both methodologies have been first tested and optimized on furfural and thus exploited on 5-hydroxymethyl-2-furfural (HMF) and 5,5’-oxy(bismethylene)-2-furaldehyde (OBMF). The syntheses of furfural, HMF and OBMF aldoximes were efficiently conducted (also in large scale) under mild reaction conditions and short reaction time. The subsequent dehydration to nitrile furanic compounds was carried out in the presence of catalytic amount of copper acetate monohydrate. Furthermore, Knoevenagel condensations were performed on furfural, HMF and OBMF with different Activated Methylene Group compounds, using for the first-time dimethyl carbonate as the reaction media. Most of the resulting products were isolated as pure via simple liquid-liquid extraction in good to excellent yields. Future applications of these compounds might include aldoxime reduction into amine furanics - herein also preliminary investigated - and hydrolysis of the nitrile derivatives in the related carboxylic acid (or ester) furanics. All these products are interesting monomers for the preparation of bio-based polymers.

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