The Synthetic Utility of Enol Derivatives and the Directed Aryltitanation of Homoallylic and Allylic Alcohols
Lee, Kathleen Marie Spivey
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This dissertation is organized in three parts. First, enol derivatives represent important building blocks for organic synthesis. Often their olefin geometry directly translates into product diastero- and enantioselectivity. Thus, stereodefined enol benzoates are subjected to the Sharpless Asymmetric Dihydroxylation to form enantiomerically enriched alpha-hydroxy aldehydes. Due to their instability, these alpha-hydroxy aldehydes are further transformed in situ to demonstrate their utility in organic synthesis. The second and third parts address the carbometalation of two types of alkenes. While the carbometalation of alkynes is a widely used transformation, the corresponding transformation for alkenes is less developed. Directing groups, such as homoallylic and allylic alcohols, may help overcome the poor reactivity of alkenes towards carbometalation. Herein the alcohols direct a highly diastereoselective aryltitanation to the proximal carbon–carbon double bond. Reactions with homoallylic alcohols result in stereospecific aryl incorporation at the terminal carbon of the double bond while the reactions with the allylic alcohol incorporate the aryl group proximal to the alcohol and generate two new sp3 centers.