Cross metathesis with acrylates: N‐heterocyclic carbene (NHC)‐ versus cyclic alkyl amino carbene (CAAC)‐based ruthenium catalysts, an unanticipated influence of the carbene type on efficiency and selectivity of the reaction. Issue 24 (23rd October 2020)

• Record Type: Journal Article
• Authors: Kaczanowska, Katarzyna; Trzaskowski, Bartosz; Peszczyńska, Aleksandra; Tracz, Andrzej; Gawin, Rafał; Olszewski, Tomasz K.; Skowerski, Krzysztof
• Is Part Of: ChemCatChem. Volume 12:Issue 24(2020)
• Page Start: 6366
• Page End: 6374
• Publication Date: 2020-10-23
• Subjects: carbenes -- cross metathesis -- cyclic alkyl amino carbene -- metathesis -- ruthenium.; Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.202001268
• Languages: English
• ISSNs: 1867-3880

Abstract

Abstract: Olefin metathesis has been widely explored as a handle for chemical diversification, a feature critical across chemical sectors. Cross metathesis (CM) with acrylic acid derivatives is an example of important but, due to the low catalyst's efficiency, industrially non‐utilized transformation. Here we report on systematic evaluation of ruthenium‐based catalysts bearing N ‐heterocyclic carbene (NHC) or cyclic alkyl amino carbene (CAAC) ligands in cross metathesis with methyl acrylate. Dramatic influence of the carbene type on the reaction's efficiency and selectivity has been found. Density functional theory (DFT) calculations suggest that the kinetic selectivity is the main factor differentiating NHC‐ and CAAC‐based ruthenium complexes. Productive turnover number (TON) of 49 900 at 10 ppm loading of nitro‐substituted Hoveyda‐Grubbs complex (nitro‐Grela catalyst) was obtained in the studied reaction, representing the highest efficiency reported to date for this transformation. High efficiency and selectivity of nitro‐Grela catalyst was then utilized in cross metathesis of trans ‐anethole with 2‐ethylhexyl acrylate to efficiently produce octyl methoxycinnamate (86 % yield), an antioxidant used in sunscreen formulations. Abstract : Cross metathesis : We report on systematic evaluation of ruthenium‐based catalysts bearing NHC carbene or cyclic CAAC ligands in CM with methyl acrylate. Dramatic influence of the carbene type on the reaction's efficiency and selectivity has been found. DFT calculations suggest that the kinetic selectivity is the main factor differentiating NHC‐ and CAAC‐based ruthenium complexes. TON of 49, 900 at 10 ppm loading of nitro‐substituted Hoveyda‐Grubbs complex was obtained in the studied reaction, representing the highest efficiency reported to date for this transformation.