Catalytic cycloisomerization of 1,5-enynes to 1,3-cyclohexadienes via ruthenium vinylidene intermediates.

Another way to dienes: The ruthenium-catalyzed 6-endo-cycloisomerization of 1,5-enynes gives the corresponding 1,3-cyclohexadienes in high to excellent yields. This novel synthetic and catalytic method constitutes another way to selectively prepare 1,3-cyclohexadienes, this cyclic diene skeleton being a core subunit in many natural products and a useful building block for a variety of organic transformations.