Ionic liquid-tagged second-generation Hoveyda-Grubbs ruthenium carbene complex as highly reactive and recyclable catalyst for ring-closing metathesis

ORGN 190

Matthew Sheets, msheets@niu.com and Qingwei Yao. Department of Chemistry and Biochemistry, Northern Illinois University, The Michael Faraday Laboratories, DeKalb, IL 60115
A second generation Hoveyda-Grubbs ruthenium carbene complex bearing an ionic liquid tag was prepared and shown to be a highly reactive catalyst for the ring-closing metathesis of di-, tri- and tetrasubstituted diene and enyne substrates in minimally ionic solvent systems ([Bmim]PF6/CH2Cl2, 1:9–1:1 v/v). Both the catalyst and the ionic liquid can be conveniently recycled and repeatedly reused (up to 17 cycles) with only a very slight loss of activity. The ionic liquid tag is crucial to the high level of recyclability of the catalyst since the original second generation Grubbs and Hoveyda-Grubbs catalysts rapidly lose their activity when recycled in the ionic liquid layer.