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Stereoretentive Olefin Metathesis

April 29, 2016 By Adam Johns

Johns, A. M.; Ahmed, T.S.; Jackson, B.W.; Grubbs, R. H.; Pederson, R.L. “High Trans Kinetic Selectivity in Ruthenium-Based Olefin Cross-Metathesis through Stereoretention” Org. Lett. 2016 18 772-775 [DOI: 10.1021/acs.orglett.6b00031]

In recent years, effective Z-selective olefin metathesis has been achieved with Ru-, W-, and Mo based organometallic complexes. Kinetic E-selective metathesis, however, has remained challenging and alternative functional group tolerant methods for the synthesis of pure trans-olefins have been developed. In a recent joint publication with the Grubbs’ group, we detail our discovery of homogenous Ruthenium metathesis catalysts that preserve olefin stereochemistry.

Poor results in an internal screen of Z-selective catalysts prompted a more detailed investigation of dithiolate-ligated ruthenium complexes.[i] Surprisingly, exposure of asymmetric internal olefins with high stereopurity (Z or E) to catalyst 1 afforded an equilibrium mixture of symmetric and asymmetric olefins while retaining the stereochemistry of the starting material in good fidelity.

figure1_sized

This transformation was successfully extended to the cross-metathesis of two internal olefins with the same stereochemistry and the cross-metathesis of a-olefins with internal olefins of defined stereochemistry. While all catalysts explored reacted more quickly with cis-olefins, a hypothesis explaining the origin of stereoretention led to structural refinements and improved catalysts.

figure2_sized

Thanks to the Grubbs group for collaborating on this publication and we look forward to future advances in stereoretentive and E-selective olefin metathesis.

[i] (a) Khan, R. K. M.; Torker, S.; Hoveyda, A. H. J. Am. Chem. Soc. 2013, 135, 10258. (b) Koh, M. J.; Khan, R. K. M.; Torker, S.; Hoveyda, A. H. Angew. Chem., Int. Ed. 2014, 53, 1968. (c) Koh, M. J.; Khan, R. K. M.; Torker, S.; Yu, M.; Mikus, M. S.; Hoveyda, A. H. Nature 2015, 517, 181.

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