Removal of PEG-Supported Ruthenium Complex by Aqueous Washing

Significance

A simple aqueous washing method to remove a ruthenium complex for the ring-closing metathesis (RCM) was developed. Thus, the RCM of 1 with poly(ethylene glycol) (PEG) supported ruthenium catalyst 2 was performed at room temperature to give crude 3 in >99% yield. Product 3 in Et₂O was washed five times with water, dried over MgSO₄, and concentrated. Leaching level of the ruthenium complex to 3 was 41 ppm (ICP analysis). The activated carbon treatment after aqueous washing reduced the ruthenium leaching level below the detection limit of the authors’ analysis (<0.04 ppm).