PerspectiveChemistry

Relay Reactions That Trap Organometallic Intermediates

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Science  14 Dec 2012:
Vol. 338, Issue 6113, pp. 1432-1433
DOI: 10.1126/science.1231509

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Summary

In 1968, Richard Heck reported (in seven remarkable consecutive papers) on palladium addition and coupling reactions that create new carbon-carbon bonds (17). These reactions and many variants became known as the Mizoroki-Heck reaction, and their use in chemical synthesis (especially of complex natural products) greatly reduced the number of reaction steps needed compared to traditional uncatalyzed reactions. Through the careful use of different transition metals, substrate partners, reaction conditions, and ligands coordinated to the transition metal, chemists can now control product formation, both where a reagent reacts on a molecule (regiochemistry) and how it reacts in a three-dimensional sense (stereochemistry). What has been rare is to combine the formation of a desired bond with the refunctionalization of the molecule at a remote site. On page 1455 of this issue, Werner et al. (8) report a stereoselective Heck reaction in which not only are the regiochemistry and stereochemistry of the reaction controlled, but a ketone is formed several bonds away through a series of relay of reactions down the substrate chain.