MECHANISM

1. HMDS deprotonates a hydrogen on the carbon adjacent to the carbonyl.
2. The negative oxygen attacks the sulfur in Tf₂O and becomes OTf.
3. Pd catalyst couples with the carbon attached to the OTf.
4. OTf and a grignard reagent couples with the Pd catalyst, removing the two chlorines.
5. The Pd catalyst leaves the system and is regenerated.