Protecting groups for thiols suitable for Suzuki conditions

The thiol group is one of the few groups NOT tolerated by the Suzuki reacti on. Therefore, a new protective group, the 2-methoxyisobutyryl group, was d eveloped by tuning the electronic/steric properties of the acyl residue. Ot her thioesters, such as thioacetate, result in a more or less dominant side reaction, which to date has not been described: sulfur-assisted acylation of boronic acids. The reaction pathway for this new reaction is discussed.