Screening of a selection of commercially available homogeneous Ru-catalysts in valuable olefin metathesis transformations

Abstract

A library of thirteen different commercially available Ru-based catalysts was evaluated in valuable metathesis reactions for the production of fragrance and bioactive molecule precursors. Rigorous library screening clearly illustrated the different catalytic behaviour of the catalyst selection and highlighted its significant advantage to provide efficiency in specific metathesis applications. Interestingly, this strategy offered substantial improvement over the state of the art, with the efficient synthesis of the macrocyclic Exaltolide 2 at low catalyst loading and dilution conditions.

Metathetic Synthesis of Common and Medium-Sized Lactones: The State of the Art

“…For instance, although high dilution of the diene ester substrates can be regarded as a convenient method to favor cyclization versus oligomerization, the use of large amount of solvent represents nowadays a serious concern. In addition, the catalyst loading is most often near 5 mol%, which can be regarded as relatively high when compared to various OM processes running nowadays at significantly lower loadings [181]. Some works have presented systematic approaches aimed at minimizing the dose of the ruthenium catalysts in the synthesis of lactones and it is now recognized that high loadings can often be detrimental to efficiency or selectivity.…”

“…In general, second-generation catalysts are by far the most effective for lactone formation in comparison with first-generation analogs, in terms of catalyst loading, reaction times, and product yields, except when catalyst endurance and/or high activity induce competitive CM or undesired subsequent transformations due to activation of internal double bonds. The concept related to match or mismatch between catalyst activity and efficiency in RCM reactions has been recently discussed in the article by Caijo et al [181]. In terms of OM reaction strategies Metathetic Synthesis of Common and Medium-Sized Lactones: The State of the Art which have addressed current issues related to atom and pot economy, the RRCM approach [60] and the RCM/ring-opening [233] sequence can be regarded as leading cases in the development of sustainable methodologies for the synthesis of lactones.…”

“…So, the catalysts were used in really low loadings (0.1 mol%) on one millimole of ester and for a short reaction time (2 h). Some selected data are reported in Table 4 [181].…”

Ultrasound-assisted self-metathesis reactions of monounsaturated fatty acids

“…1, entry 3) (Love et al, 2002) and Omega Cat System catalysts C4-C6 (Tab. 1, C4-C6) (Caijo et al, 2013). However, the use of these catalysts resulted in slightly lower yields of (2) and (3).…”

Regio‐ and Enantio‐selective Chemo‐enzymatic C−H‐Lactonization of Decanoic Acid to (S)‐δ‐Decalactone

“…[21,22] A number of stereoselective biocatalytic methods have been reported for these lactones,i ncluding use of Baeyer-Villiger monooxygenases, [23] alcohol dehydrogenases,and biocatalytic cascades. [26][27][28][29] Thee xtraction of Massoia lactone from Cryptocaria massoia poses environmental concerns, [30] whereas the chemical synthesis requires transition-metal catalysts,peracids,and organic solvents. [26][27][28][29] Thee xtraction of Massoia lactone from Cryptocaria massoia poses environmental concerns, [30] whereas the chemical synthesis requires transition-metal catalysts,peracids,and organic solvents.…”