NCN–Pincer–Pd Complex as Catalyst for the Hiyama Reaction in Biomass-Derived Solvents

Abstract

A NCN-pincer-Pd complex have been synthetized and applied to Hiyama-type cross-coupling reactions between aryl halides and different types of organosilanes using neoteric solvents. This report constitutes a green approach to cross-coupling reactions since the reagents employed are stable and non-toxic. The solvents used (Deep Eutectic Solvents based on choline chloride or glycerol) are also biodegradable, non-toxic, non-flammable and biorenewable. Furthermore, the catalytic system can be recycled, allowing to perform the reaction for at least three cycles without adding more catalyst or solvent, increasing the value of the process from an economical and environmental point of view. The effect of these solvents on the catalytic activity has been studied. Finally, a gram-scale reaction has also been tested affording biaryl products in high yields and purity by a simple liquid-liquid extraction, without the need of aqueous work-up or chromatographic steps, proving the applicability of this approach in a sustainable industrial scale.

Palladium Mesoionic Carbene Pre-catalyst for General Cross-Coupling Transformations in Deep Eutectic Solvents

“…Surprisingly, no inhibition at all was observed in the case of the Hiyama coupling. A similar result was previously observed employing a Pd NCN-pincer in DES (Marset et al, 2018).…”

“…The Suzuki reaction in DES have been accomplished also with lower Pd(OAc) 2 loadings by employing aryltrifluoroborates instead of boronic acids (Dilauro et al, 2018) as well as in the aminocarbonylation of aryl iodides (Messa et al, 2018). Our group have also contributed to this research field with the Hiyama reaction performed with a robust NCN-Pd pincer catalyst in ChCl:glycerol (Marset et al, 2018). However, the use of ionic phosphines seems to increase the compatibility of the palladium pre-catalysts with the reaction media, as it has been proven by the use of anionic TPPTS ligand, which was followed by enzymatic catalyzed reactions (Paris et al, 2018, 2019).…”

Palladium‐Based Catalysts Supported by Unsymmetrical XYC–1 Type Pincer Ligands: C5 Arylation of Imidazoles and Synthesis of Octinoxate Utilizing the Mizoroki–Heck Reaction

“…TON) transition‐metal based catalysts because it allows the use of minimum amounts of toxic or might be precious transition metals Organometallic palladium complex catalyzed C–C bond‐forming reactions are essential and frequently exploited in syntheses of pharmaceuticals and organic materials on both in laboratories as well as in industry . Several functionalized organometallic palladium complexes have been reported for various reactions namely hydrogenations, hydrophosphinations, C–H functionalization, Hiyama reaction, Suzuki–Miyaura reactions, Sonogashira coupling reactions Mizoroki–Heck reactions and Buchwald–Hartwig reactions etc.…”

A Bipyridine‐Palladium Derivative as General Pre‐Catalyst for Cross‐Coupling Reactions in Deep Eutectic Solvents

“…[8] Although, a pincer-type palladium catalyst was effective for the aforementioned reaction. [9] Scheme 1. Previous work of cross-coupling reactions in DES.…”