A Metallacycle Fragmentation Strategy for Vinyl Transfer from Enol Carboxylates to Secondary Alcohol C-H Bonds via Osmium- or Ruthenium-Catalyzed Transfer Hydrogenation.

A strategy for catalytic vinyl transfer from enol carboxylates to activated secondary alcohol C–H bonds is described. Using XPhos-modified ruthenium(0) or osmium(0) complexes, enol carboxylate–carbonyl oxidative coupling forms transient β-acyloxy-oxametallacycles, which eliminate carboxylate to deliver allylic ruthenium(II) or osmium(II) alkoxides. Reduction of the metal(II) salt via hydrogen transfer from the secondary alcohol reactant releases the product of carbinol C–H vinylation and regenerates ketone and zero-valent catalyst.