Intermolecular Heck Coupling with Hindered Alkenes Driven by Carboxylate Directivity
Pd(0)-catalyzed, non-chain-walking Mizoroki-Heck reactions exhibit poor reactivity with polysubsti- tuted, unbiased alkenes. Intermolecular reactions with simple, all-carbon tetrasubstituted alkenes are unprecedented. Here we report that pendant carboxylic acids, combined with bulky monophospine ligands on palladium, can direct the arylation of tri- and tetrasubstituted olefins. Quaternary carbons are established at high Fsp3 attached-ring junctures and the carboxylate directing group can be removed after coupling. Carboxylate directivity prevents over-arylation of the new, less hindered alkene, which can be diversified in subsequent reactions.