Protecting Groups for Thiols Suitable for Suzuki Conditions.

The thiol group is one of the few groups NOT tolerated by the Suzuki reaction. Therefore, a new protective group, the 2-methoxyisobutyryl group, was developed by tuning the electronic/steric properties of the acyl residue. Other 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.