Ruthenium-Based Complexes Bearing Quaternary Ammonium Tags as Versatile Catalysts for Olefin Metathesis: From the Discovery to Practical Applications

Abstract

This personal account describes the development and fine-tuning of pH-neutral quaternary-ammonium-tagged ruthenium-based complexes, their use as versatile catalysts for olefin metathesis, and the application of that transformation in the synthesis of complex molecules.

Catalytic olefin metathesis in blood

“…In addition, the catalytic RCM for substrate 1 was tested in a mixture that contained 80% blood, and AlbRu–I still showed high activity (entry 6). A highly water-soluble Ru complex, AquaMet catalyst, 31 has been shown to effectively catalyze RCM in aqueous media. However, as expected by the report of Schwaneberg, 32 the reactivity of the AquaMet catalyst in the blood mixture was completely abolished (entry 7).…”

Ruthenium Olefin Metathesis Catalysts Featuring N-Heterocyclic Carbene Ligands Tagged with Isonicotinic and 4-(Dimethylamino)benzoic Acid Rests: Evaluation of a Modular Synthetic Strategy

“…At the same time, the introduction of such a tag could allow the catalyst easier removal after reaction, if the system is used under homogeneous conditions [21]. The most popular method for tagging of ruthenium benzylidene catalysts is to modify the NHC ligand or the benzylidene fragment [17,18,21]. As the benzylidene ligand dissociates in the first step of the catalytic cycle, the NHC ligand-the one which is bound to the ruthenium throughout the whole process-was chosen by us as the preferred handle for a tag.…”

“…An attractive solution for the latter issue is the heterogenization of the catalyst on solid (or liquid) supports. Over the past decades, both covalent [15,16] and non-covalent [17,18] anchoring of the catalyst to the support has been explored (Figure 1) [19][20][21]. Covalent immobilization is often accompanied with the costly development of sophisticated linkers, in catalysts as well as supports [22].…”

Protocol for olefin metathesis reactions of hydrophobic substrates performed in aqueous emulsion with mechanical stirring or with microwaves support

“…A similar strategy involved specially designed catsurfs (catalyst+surfactant) – catalysts able to acting simultaneously as initiators and surfactants ( Gawin et al., 2010 ). Recently, several water-soluble catalysts have also been presented, gained by incorporation of ionic tags or PEGs into classical catalysts structure ( Hong and Grubbs, 2006 ; Olszewski et al., 2020 ; Skowerski et al., 2012 ; Wang et al., 2015 ). Nevertheless, relatively high loading of these tailor-made catalysts is usually required.…”