Consequent Construction of C–C and C–N Bonds via Palladium-Catalyzed Dual C–H Activation: Synthesis of Benzo[c]cinnoline Derivatives

Abstract

A highly efficient palladium-catalyzed cascade annulation of pyrazolones and aryl iodides to access various benzo­[c]­cinnoline derivatives has been achieved at 80 °C. A pyridine-type ligand could improve the reaction efficiency under current reaction conditions, giving a higher product yield up to 94%. This novel approach provided a one-pot dual C–H activation strategy with good functional group tolerance, such as halogen, methoxy, nitro, ester, phenol, and so forth. The product could readily convert into cinnoline derivatives.

Construction of Phenanthridinone Skeletons through Palladium-Catalyzed Annulation

“…Such poor regioselectivity indicates that the reaction proceeds through arynes as the key intermediates, as has been proposed for related transformations featuring palladium catalysis. 18 Based on the literature precedents, 19 a plausible mechanism that does not contradict the above control reactions is proposed ( Scheme 2 , bottom left ). Initially, base-assisted oxidative addition of 2-bromobenzoic acid 2 to Pd 0 provides the key aryl-Pd II species I .…”

Derivation of Benzothiadiazine‐1,1‐dioxide Scaffolds via Transition Metal‐Catalyzed C—H Activation/Annulation

“…Pyrazolidinones are one of the most important structures frequently found in a variety of drugs. [ 17‐20 ] For instance, edaravone can scavenge free radicals and is used clinically for brain protection. [ 21 ] Spiropyrazolones represent a promising drug‐like framework with potential biological activities such as antitumor, anti‐inflammatory, antibacterial and analgesic activities [ 22‐30 ] (Figure 1b).…”

Hydrazine–Halogen Exchange Strategy Toward N═N-Containing Compounds and Process Tracking for Mechanistic Insight

“…In recent years, CN coupling of protected hydrazine has emerged as a promising method for preparing ABs − and cinnolines; − however, they suffer from inevitable extra steps for protection as well as deprotection, leading to low step economy and efficiency. Direct use of N 2 H 4 ·H 2 O as a N 2 source to assemble NN compounds is a green and efficient way but has not been reported.…”