Exit Suzuki, exit Stille

09 August 2013 - Superseded by

For the synthesis of new compounds synthetic organic chemists rely on a whole bunch of coupling reactions. In two of them, one reactant is an aryl bromide and the other a organoboron compound in the Suzuki coupling and an organotin compound in the Stille coupling. Giannerini et al. (Ferenga lab) note here that these starting materials often derive from the same organolithium compound, so why not try out coupling reactions using organolithium compounds in the first place?
Things to watch out for according to Giannerini: ease of homocoupling and ease of lithium - bromide exchange resulting in dehalogenation. Proper choice of solvent should control RLi aggregation state and therefore reactivity and therefore toluene was selected as solvent. A combination of in-situ combined tris(dibenzylideneacetone)dipalladium(0) and tri(tert-butyl)phosphine was found to be very effective. Interestingly commercially available Pd(tBu3P)2 did not perform as well in several cases.

Because RLi compounds are highly reactive the reaction can now take place at room temperature and turns out to be very fast. Given the wide availability of organolithiums and affordability it seems the Stille and Suzuki couplings face an uncertain future.

Note added: Reader T. disagrees, with substrates with various functional groups Suzuki is still the way to go. This blog agrees! headline too sensational!
Aryllithium cross coupling  Feringa 2013.PNG