Oxygen-promoted coupling of arylboronic acids with olefins catalyzed by [CA]2[PdX4] complexes without a base

Abstract

a b s t r a c tAn efficient method was developed for the oxidative Heck reaction between arylboronic acids and olefins catalyzed by anionic palladium complexes of the type [CA] x [PdCl 4 ] (x = 1,2) and [CA] 2 [Pd 2 Cl 6 ] (CA = imidazolium or pyridinium cation). Molecular oxygen was employed as an environmentally benign oxidant to regenerate Pd(II) species during the reaction. The elaborated protocol could be applied to the coupling of different arylboronic acids with both electron-rich and electron-poor olefins. The catalyst system was further employed for the one-pot oxidative Heck reaction followed by the Heck coupling to build conjugated compounds in good yield.Mass spectrometry (ESI-MS) and UV-vis spectroscopy was used to identify palladium-containing complexes in the reactions. A plausible reaction mechanism of the oxidative Heck reaction was proposed.

Ligand‐free palladium‐catalyzed tandem pathways for the synthesis of 4,4‐diarylbutanones and 4,4‐diaryl‐3‐butenones under microwave conditions

“…Our approach, presented in this paper, was based on a tandem process involving two arylation steps with the same catalyst, without the isolation of the first aryl ketone (Figure ). The second modification consisted in the application of MW irradiation instead of conventional heating . It was expected that this would shorten the reaction time and save energy.…”

“…The second modification consisted in the application of MW irradiation instead of conventional heating. [12,[45][46][47] It was expected that this would shorten the reaction time and save energy.…”

Proximity Effect using a Nanocage Structure: Polyhedral Oligomeric Silsesquioxane‐Imidazolium Tetrachloro‐ palladate Salt as a Precatalyst for the Suzuki–Miyaura Reaction in Water

“…In situ ESI‐MS experiments showed evidence of [(IL) x Pd 3 ] cluster formation if complexes of the type [IL] 2 [PdX 4 ] were used as catalyst precursors . Other anionic Pd complexes of the type [IL] 2 [PdX 4 ] have been reported and used as pre‐catalysts in the Suzuki–Miyaura reaction, in the oxidative Heck reaction and other catalytic applications . Recently, inorganic–organic hybrid materials have attracted great interest thanks to their excellent performance in terms of thermal and mechanical stability.…”

Oxidative and Reductive Cross-Coupling Reactions Catalyzed by an Anionic “Ligandless” Palladium Complex

“…We performed an in-depth analysis of the reasons for the high catalytic activity, which explained the higher activity of 1a compared with 1b and 1c and suggested that complex 1a might also be suitable for other cross-coupling reactions. Earlier results by Dyson , and Trzeciak, − among others, − on related anionic palladium complexes support this suggestion (Scheme d).…”