Olefin metathesis in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate using a recyclable Ru catalyst: Remarkable effect of a designer ionic tag

Designer labels: Ruthenium carbene complex 1 bearing an ionic tag was shown to be a highly reactive catalyst for the ring-closing metathesis of various diene and enyne substrates in minimally ionic solvent systems (see scheme; Bmim = 1-butyl-3-methylimidazolium, Ts=toluene-4-sulfonyl). The catalyst can be repeatedly recycled and reused (up to at least 10 cycles) without significant loss of its activity, whereas other catalysts tested exhibited a dramatic diminishment in their activity upon recovery from the ionic layer.