The Metal Tin Promoted Cascade Reaction of Ketones in Aqueous Media for the Construction of 2-Bromo-4-aryl-1,3-pentadiene.

A novel type of transformation was discovered serendipitously during the Barbier-type allenylation reaction of aromatic ketones promoted by the metal, tin, in aqueous media. Additionally, a series of new, highly functionalized 2-bromo-4-aryl-1,3-pentadienes could be obtained with good yields in this reaction. This cascade reaction shows the unique properties of the metal, tin. Furthermore, it is actually a cascade reaction which involves two steps: one is the Barbier-type allenylation of the carbonyl compound, and the other is an SN2′ type addition–elimination reaction. Notably, this reaction has the advantages of simple, mild conditions and is easy to operate. Furthermore, the corresponding product could be applied to various coupling reactions or other diversified transformations.