Transformation from intermediate 3 to 4 in the synthesis of Vinigrol
Maimone, T. J.; Shi, J.; Ashida, S.; Baran, P. S. J. Am.Chem. Soc. 2009, 131, 17066-17067.
Just as a side note, The first step of the mechanism forms an enolate, not the carbanion shown. We decided not to change the mechanism video because it was already published as a carbanion species, but the actual mechanism would involve an enolate.