Aldehydes and ketones that have oxygen substituents at the alpha-position are important building blocks for the synthesis of a large number of biologically active compounds. Conventional transformations which afford the alpha-oxygenation products of carbonyl compounds either utilize oxidants that are unstable or involve the removal of halogenated byproducts after displacement with oxygen nucleophiles. We have developed a new alternative route to alpha-oxygenated carbonyl compounds through the dioxygenation of vinyl boronic acids which avoids the use of unstable reagents, undesirable side-products and provides a direct route from internal alkynes to alpha-oxygenated ketones. The use of  N-hydroxyphthalimide to afford the dioxygenation of vinyl boronic acids will be presented: a two-step procedure involving the copper-catalyzed etherification of N-hydroxy phthalimide with boronic acids and a subsequent [3,3] rearrangement of the N-enoxyphthalimide coupling products will be described.  The stereoselectivity of the rearrangement to form the alpha-oxygenated ketones and aldehydes as well as simple procedures for the cleavage of the alpha-imidate products to give alpha-hydroxy ketones in good yields will also be discussed.

Synthesis of alpha-hydroxy ketones and aldehydes via the dioxygenation of vinyl boronic acids

244th National Meeting (2012)

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