Ru-Catalyzed (E)-Specific ortho-C-H Alkenylation of Arenecarboxylic Acids by Coupling with Alkenyl Bromides

In the presence of [p-cymene)RuCl2](2), (E)-configured alkenyl bromides couple with aromatic carboxylates to form orthovinylbenzoic acids. This C-H vinylation proceeds in high yields without any activating phosphine ligands and has an excellent functional group tolerance. Starting from commonly available (E/Z)-mixtures of alkenyl bromides, (E)-configured vinyl arenes or dienes are formed exclusively. Mechanistic studies show that this selectivity is achieved because the (E)configured alkenyl bromides undergo a smooth coupling, whereas the (Z)-isomers are rapidly eliminated with the formation of alkynes.

Automated summary

In the presence of [p-cymene)RuCl2](2), (E)-configured alkenyl bromides coupled with aromatic carboxylates to form orthovinylbenzoic acids in high yields, showing excellent functional group tolerance. Mechanistic studies revealed that the selectivity of this reaction is due to (E)-configured alkenyl bromides undergoing smooth coupling while the (Z)-isomers are rapidly eliminated to form alkynes.