Rh(III)-Catalyzed C-H Annulation of Alkenyl- or Arylimidazoles and (Hetero)cyclic 1,3-Dicarbonyl Compounds: A Rapid Access to Imidazo-Fused Polycyclic Compounds.

A novel strategy for the synthesis of imidazo-fused polycyclic compounds under mild, base-free, and silver-free conditions by a rhodium(III)-catalyzed C-H annulation of alkenyl or arylimidazoles and (hetero)cyclic 1,3-dicarbonyl compounds is reported here. Such a step-economic protocol features the selective cleavage of two different C-H bonds in one step, featuring easy operation, readily available starting materials, gram-scale synthesis, broad functional group tolerance, and no requirement to presynthesize carbene precursors. Notably, the synthetic potential is showcased by the structural modification of drug and the highly step-economic synthesis of Janus kinase inhibitor in only three steps with a satisfactory 26% total yield (previous method: in nine steps with 0.6% yield).