posted on 2023-12-22, 15:05authored byWei-Jung Chiu, Ting-Yen Chu, Indrajeet J. Barve, Chung-Ming Sun
The synthesis of pyrazolone-fused cinnolines from pyrazol-3-ones
and α,γ-substituted allenoates via a palladium-catalyzed
C–H activation/annulation cascade was developed. Mechanistic
studies revealed the course of the reaction. Initially, N-acyl-valine ligand-assisted ortho-C–H activation
gives ortho-alkenylated intermediate. Subsequent
cyclopalladation and migratory insertion of allenoate give a seven-membered
palladacycle. Reductive elimination finally furnishes pyrazolone-fused
cinnolines.