One-pot Negishi cross-coupling reaction of aryldiazonium salts via Ni catalysis induced by visible-light

Nickel-Catalyzed Cross-Coupling of Aryl Diazonium Salts with Aryl Bromides

Herein, we present a one-pot method for the direct cross-coupling of aryl diazonium salts and aryl bromides in an economical way that avoids the use of sensitive organometallic reagents. The reaction is accomplished with the assistance of nickel catalysts, ligands, magnesium turnings, lithium chloride, and triethylamine, avoiding the use of pre-activated organometallic reagents.

Low-cost transition metal catalysed Negishi coupling: an update

The Negishi coupling is a significant C-C bond-forming reaction to access synthetically valuable organic compounds. In recent years, researchers have developed sustainable first-row transition metal (Fe, Co, Ni and Cu) based complexes in place of the conventional Pd catalyst for this reaction. Several such low-cost metal-based catalysts showed high efficiency and potential application in natural product synthesis. This review focuses on the recent achievements in low-cost transition metal-based Negishi coupling reactions, covering reports from 2016.

Pd-Catalyzed Cross-Couplings: On the Importance of the Catalyst Quantity Descriptors, mol % and ppm

This Review examines parts per million (ppm) palladium concentrations in catalytic cross-coupling reactions and their relationship with mole percentage (mol %). Most studies in catalytic cross-coupling chemistry have historically focused on the concentration ratio between (pre)catalyst and the limiting reagent (substrate), expressed as mol %. Several recent papers have outlined the use of “ppm level” palladium as an alternative means of describing catalytic cross-coupling reaction systems. This led us to delve deeper into the literature to assess whether “ppm level” palladium is a practically useful descriptor of catalyst quantities in palladium-catalyzed cross-coupling reactions. Indeed, we conjectured that many reactions could, unknowingly, have employed low “ppm levels” of palladium (pre)catalyst, and generally, what would the spread of ppm palladium look like across a selection of studies reported across the vast array of the cross-coupling chemistry literature. In a few selected examples, we have examined other metal catalyst systems for comparison with palladium.

Aryl Diazonium Salts: Powerful Arylating Agents for Catellani-Type ortho-Arylation

The Catellani reaction provides an efficient synthetic approach to polyfunctionalized arenes. However, the selective ortho-arylating reagents employed in these reactions have been strictly limited to activated bromoarenes. As demonstrated in this work, aryl diazonium salts bearing both electron-donating and electron-withdrawing substituents, after in situ transformations with KI into the corresponding iodoarenes, were efficient arylating reagents for Catellani type ortho-arylation approaches.

Carbazole based Electron Donor Acceptor (EDA) catalysis for the synthesis of biaryl and aryl-heteroaryl compounds

A highly regioselective, carbazole based Electron Donor Acceptor (EDA) catalyzed synthesis of biaryl and aryl-heteroaryl compounds is described. Various indole and carbazole derivatives were screened for the Homolytic Aromatic Substitution (HAS) reaction. Tetrahydrocarbazole (THC) was very efficient for the HAS transformation and proceeded via a complex formation between diazonium salt and electron rich tetrahydrocarbazole. The UV-Vis spectroscopy technique has been used to confirm the complex formation. The in situ generated EDA complex even in a catalytic amount is found to be efficient for the Single Electron Transfer (SET) process without any photoactivation. Biaryl compounds, 2-phenylfuran, 2-phenylthiophene, and 2-phenylpyrrole and bioactive compounds such as dantrolene and canagliflozin have been synthesized in moderate to excellent yields.