Organocatalytic upgrading of the key biorefining building block by a catalytic ionic liquid and N-heterocyclic carbenes

The present study of rapid degradation of the key biorefining building block 5-hydroxymethylfurfural (HMF) in an ionic liquid (IL), 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc), has led to highly selective and efficient upgrading of HMF to 5,5′-di(hydroxymethyl)furoin (DHMF), a promising C 12 kerosene/jet fuel intermediate. This HMF upgrading reaction is carried out under industrially favourable conditions ( i.e. , ambient atmosphere and 60-80 °C), catalyzed by N-heterocyclic carbenes (NHCs), and complete within 1 h; this process selectively produces DHMF with yields up to 98% (by HPLC or NMR) or 87% (unoptimized, isolated yield). Mechanistic studies have yielded four lines of evidence that support the proposed carbene catalytic cycle for this upgrading transformation catalyzed by the acetate IL and NHCs. Detrimental degradation of HMF in the acetate ionic liquid is turned into highly selective and efficient biorefinery upgrading into DHMF, a promising C 12 kerosene/jet fuel intermediate, through N-heterocyclic carbene catalysis.