A Zwitterionic Palladium(II) Complex as a Precatalyst for Neat‐Water‐Mediated Cross‐Coupling Reactions of Heteroaryl, Benzyl, and Aryl Acid Chlorides with Organoboron Reagents

Abstract

The Suzuki–Miyaura cross‐coupling (SMC) reactions of several heteroaryl chlorides, benzyl chlorides, and aryl acid chlorides with (hetero)arylboron reagents have been investigated in the presence of [Pd(HL1)(PPh3)Cl2] (I) [HL1 = 3‐[(2,6‐diisopropylphenyl)‐1‐imidazolio]‐2‐quinoxalinide] as catalyst and K2CO3 as base in neat water. The synthesis of the heterocycle‐containing biaryls required the addition of 2 mol‐% of a phosphine ligand (PPh3 or X‐Phos). A combination of more than 115 substrates were screened and it was found that I is a versatile catalyst that can produce heterocycle‐containing biaryls, diarylmethanes, and benzophenones in moderate‐to‐excellent yields.

Synthesis of Biaryls via Decarbonylative Palladium-Catalyzed Suzuki-Miyaura Cross-Coupling of Carboxylic Acids

“…17, 153.37, 149.65, 148.82, 135.98, 132.26, 127.54, 126.52, 125.19, 123.98, 123.51, 123.43, 123.03, 122.36, 120.81, 120.62, 111.89. The spectral data matched those reported in the literature (Ramakrishna et al, 2017). 138.13, 137.10, 130.10, 129.67, 128.60, 127.12, 126.81, 52.11, 21.18.…”

Synthesis of dihydroisoquinolinone-4-methylboronic esters via domino Heck/borylation using a structurally characterized palladacycle as a catalyst

“…We have recently reported the synthesis of zwitterionic palladium complexes and their catalytic efficiency in Suzuki–Miyaura cross coupling (SMC) reactions. 11 In order to explore the mechanistic details of those reactions two quinoxaline based NHC-palladacycles were synthesized. It was found that these palladacycles were less efficient than the precursor imidazolium zwitterionic complexes in catalyzing the SMC reactions.…”

Latest Developments on Palladium- and Nickel-Catalyzed Cross-Couplings Using Aryl Chlorides: Suzuki–Miyaura and Buchwald–Hartwig Reactions

“…13 This reaction was applied to electron-deficient aryl chlorides only, while the products were obtained in up to 98% yield. Reddy et al developed a zwitterionic Pd(II) complex C4 (0.5 mol%) and utilized it for SM couplings of aryl or heteroaryl chlorides, 14 where triphenylphosphine (PPh 3 ) (2 mol%) was used as an additional ligand. The reactions of multiple heterocyclic aryl chlorides, including pyridine, pyrazine, quinoline, isoquinoline, and thiophene, afforded cross-coupling products 17-24 in yields of 80-95% (Scheme 6).…”