Their novel approach eschews the need to use stoichiometric amounts of allyl-metal reagents in such reactions, and it enhances the versatility of such syntheses by making it possible to couple allyl moieties with aldehydes generated in situ from alcohols, something that couldn't be done before. In an organic chemist's toolbox of carbon-carbon bond forming reactions, carbonyl allylation is a handy resource for constructing complex molecules. The transformation provides quick and easy access to homoallylic alcohols, which are important intermediates en route to medicinally relevant compounds such as polyketides. The new carbonyl allylation methods, invented by chemistry professor Michael J. Krische and colleagues, employ allyl acetate or 1,3-dienes as surrogates for allyl-metal reagents. In the presence of an iridium or a ruthenium catalyst, respectively, these reagents will combine with primary alcohols to generate homoallylic alcohols. In the case of the iridium-catalyzed reaction, the process is enantioselective. Previous examples of carbonyl allylation worked only with aldehydes, but Krische's method works with both aldehydes and alcohols.
by Bethany Halford |
May 12, 2008