Abstract:
A chitosan-derived metal-free N-doped carbon catalyst was
synthesized and investigated for selective reductive formylation
of quinoline to N-formyl-tetrahydroquinoline and nitroarenes to
N-formyl anilides via aqueous formic acid (FA)-mediated
catalytic transformation. FA dissociated on the catalyst surface
and acted as a hydrogenating and formylating source for
selective N-formylation of N-heteroarenes. The carbonized
catalyst prepared at 700°C offered the best activity. A 92% yield
of N-formyl-tetrahydroquinoline after 14 h and >99% yield for
N-formyl anilide after 12 h at 160°C were obtained. The
excellent catalytic activity was correlated with the type of “N”
species and the basicity of the catalyst. Density functional
theory calculations revealed that a water-assisted FA decomposition pathway (deprotonation and dehydroxylation) generated the surface adsorbed H and HCOO species, required for
the formation of N-formylated products. In addition, the
selective formation of N-formyl-tetrahydroquinoline and Nformyl anilides was explained by a comprehensive reaction
energetics analysis.
