Me2Zn-mediated addition of acetylenes to aldehydes and ketones

[reaction: see text] Contrary to expectations, commercially available 2 M Me2Zn in toluene is able to promote the addition of phenylacetylene to aldehydes and ketones. This reactivity is determined by a new, unprecedented mechanism, which involves activation of the zinc reagent via coordination with carbonyl substrates that behave "ligand like". Broad scope, high tolerance to functional groups, and a simple procedure make this new method highly interesting for the synthetic chemist.