—Carbene Size Guides Coupling “Organometallic Chemistry: Ligand bulk affects outcome of aldehyde-alkyne pairing” With the help of carbene ligands, chemists have found new ways of controlling cross-coupling reactions that lead to allylic alcohols. Choosing either large or small ligands for a nickel catalyst helps define which region of an alkyne will couple to an aldehyde to form the alcohol, a level of control synthetic chemists have traditionally found difficult to achieve. Allylic alcohols are common motifs in antibiotics and other pharmaceuticals, and although chemists have developed catalytic and enantioselective couplings of aldehydes and alkynes, controlling the regiochemistry of such metal-catalyzed couplings is still not straightforward. To avoid getting mixtures of products, researchers must turn to alkynes that are highly biased toward one outcome or the other or that have directing groups.
by Carmen Drahl |
April 23, 2010