Streamlined Routes to Phenacyl Azides and 2,5-Diarylpyrazines Enabled by Deep Eutectic Solvents

A Deep Eutectic Solvent like choline chloride/glycerol (1:2 mol mol(-1)) proved to be an effective, sustainable reaction medium to easily synthesize both phenacyl azides and symmetrical 2,5-diarylpyrazines of interest in pharmacology and in coordination chemistry. Notable features of our report include: (i) nucleophilic substitution reactions of alpha-halo carbonyl compounds to the corresponding phenacyl azides compatible with the eutectic mixture, (ii) the reduction of phenacyl azides to alpha-amino carbonyl compounds, which undergo spontaneous dimerisation/cyclisation/aromatisation in the same eutectic mixture to provide valuable pyrazines. Telescoped, one-pot, two-steps stoichiometric/catalytic processes have also been successfully developed to furnish 2,5-diarylpyrazines in up to 95 % yield.