Diversified upgrading of HMF via green acetylation, aldol condensation, carboxymethylation, vinylation and reductive amination reactions

Multiple sustainable methodologies were developed for the chemical upgrading of HMF: i) at 30-90 degrees C, highly selective base-catalyzed acetylation and carboxymethylation reactions of HMF with nontoxic reagents as isopropenyl acetate (iPAc) and dimethyl carbonate (DMC) were achieved to prepare the corresponding ester and carbonate products, (5-formylfuran-2-yl)methyl acetate (5-formylfuran-2-yl) methyl carbonate, respectively; ii) based on the combined use of iPAc/DMC with acetone, a tandem protocol of acetylation/transcarbonation and aldol condensation was designed to synthesize a variety of HMF-derived alpha,beta-unsaturated carbonyl compounds; iii) in water as a solvent, a chemoselective Pd-catalysed reductive amination of HMF with amino-alcohols also including glycerol derivatives, was developed using H-2 at atmospheric pressure; iv) finally, both HMF and its ester and carbonate products successfully underwent Wittig vinylation reactions promoted by a methyl carbonate phosphonium salt ([Ph3PCH3] [CH3OCO2]), to obtain the corresponding olefins. The vinylation reagent (the salt) was a DMC derivative. In all cases i-iv), not only processes occurred under mild conditions, but post-reaction procedures (work-up and purification) were optimized to isolate final products in high yields of 85-98%.