Pd(II)-Catalyzed Synthesis of Polycyclic Heteroarenes via an Aminopalladation/C–H Activation/Dealkylation/Decarboxylative Cyclization Cascade

Abstract

Until now, cascade reactions involving five-membered C,C-palladacycles rely heavily on Pd(0)-catalyzed C–H functionalization of aryl halides initiated by carbopalladation. Herein, we report a novel Pd­(II)-catalyzed cascade decarboxylative cyclization of o-alkynylanilines initiated by aminopalladation. In this protocol, o-alkynylanilines undergo sequential anti aminopalladation, C–H activation, and dealkylation to form C,C-palladacycles, which are then trapped by o-bromobenzoic acids or 8-bromo-1-naphthoic acid to produce diverse polycyclic heteroarenes, such as dibenzo­[a,c]­carbazoles and multiple arene-fused cyclohepta­[1,2-b]­indoles.

Palladium Catalysis: Dependence of the Efficiency of C–N Bond Formation on Carboxylate Ligand and Metal Carboxylate or Carboxylic Acid Additive

“…Using palladium, copper, and potassium acetates or pivalates in DMA under oxygen, Liang, Yang, and co-workers 26 performed the decarboxylative domino reaction of o -(phenylethynyl)aniline 10a with o -bromobenzoic acid, which afforded dibenzo[ a , c ]carbazole 10a1 ( Scheme 10 a). The best yield arose using catalytic amounts of Pd(OAc) 2 with overstoichiometric amounts of both Cu(OCO t -Bu) 2 and KOCO t -Bu.…”

Oxidative Tandem Cyclization of Aromatic Acids with (Benzo)thiophenes: One-Pot Access to Planar Sulfur-Containing Polycyclic Heteroarenes for Lipid-Droplet-Targeted Probes

“…π-Conjugated polycyclic heteroarenes (PHAs) have attracted widespread interest in the fields of synthetic chemistry and optoelectronic materials due to their unique photophysical, electronic, and electrochemical properties . Due to their lower aromaticity, sulfur-containing PHAs exhibit a larger band gap and higher oxidation stability.…”