An efficient macrolactonization protocol devoid of any base was developed derived from the use of vinyl esters in transesterification. Subjecting a hydroxy acid and ethoxyacetylene to 2 mol%[RuCl2 (p-cymene)] 2 in toluene followed by addition of camphorsulfonic acid or inverse addition provided macrolactones in good yields.
[Trost, Barry M.; Wrobleski, Stephen T.; Chisholm, John D.; Harrington, Paul E.; Jung, Michael Journal of the American Chemical Society, 2005 , vol. 127, # 39 p. 13589 - 13597]
