Why Is the Suzuki−Miyaura Cross-Coupling of sp³Carbons in α-Bromo Sulfoxide Systems Fast and Stereoselective? A DFT Study on the Mechanism

The stereoselectivity-determining oxidative addition step in the Suzuki-Miyaura cross-coupling of alpha-bromo sulfoxides is analyzed computationally through DFT calculations on a model system defined by Pd(PMe(3))(2) and CH(3)SOCH(2)Br. Both monophospine and bisphosphine complexes have been considered, different reaction pathways being characterized through location of the corresponding transition states. The lowest energy transition states correspond to nucleophilic substitution mechanisms, which imply inversion of configuration at the carbon, in good agreement with experimental data on the process. The energy-lowering and stereodirecting role of the sulfinyl substituent is explained through its attractive interactions with the palladium center, which are only possible in the most favored mechanisms.