Diols, α‑Ketols, and Diones as 22π Components in [2+2+2] Cycloadditions of 1,6-Diynes via Ruthenium(0)-Catalyzed Transfer Hydrogenation

The first use of vicinal diols, ketols, or diones as 22π components in metal-catalyzed [2+2+2] cycloaddition is described. Using ruthenium(0) catalysts, 1,6-diynes form ruthena­cyclo­penta­dienes that engage transient diones in successive carbonyl addition. Transfer hydrogenolysis of the resulting ruthenium­(II) diolate mediated by the diol or ketol reactant releases the cycloadduct with regeneration of ruthenium(0) and the requisite dione.