Synthesis of amine derivatives from furoin and furil over Ru/Al2O3 catalyst

The direct/reductive amination of carbohydrate-based furoin and furil with NH3/H2 was investigated to access amine derivatives. In the sole presence of NH3, cyclic amines, i.e. 2,3,5,6-tetra(furan-2- yl)pyrazine and 2,2’-bipyridine-3,3’-diol, were generated as main products from furoin and furil, respectively. Over Ru/Al2O3 under NH3/H2, 2-amino-1,2-di(furan-2-yl)ethan-1-ol (i.e. alcohol-amine) was generated as main product with 47% yield at 140 °C for 2 h starting from furoin. The catalyst could be recycled for at least three consecutive runs. An alcohol-imine was the main interme- diate that undewent tautomerization to alcohol-enamine/keto- amine leading to cyclic by-products by self-condensation. DFT calculations, complementing the experimental observations, provide a detailed molecular-level insight into the reactivity of the alcohol-imine intermediate. Its preferential adsorption on Ru centers via the NH group with the OH group pointing away from the surface, directs the reaction pathway towards the formation of alcohol-amine as main product. By combining Ru/Al2O3 and a silica-anchored N-heterocyclic carbene (NHC) catalyst, 2-amino- 1,2-di(furan-2-yl)ethan-1-ol could be accessed with 42% overall yield in a single reactor.