Haloaldol reactions involving the addition of allenyl esters to aldehydes and ketones were achieved for the first time with high diastereoselectivity. Optimization studies of this reaction revealed that Ti(IV) chloride leads to the optimal diastereoselective outcome. In addition, the utilization of an α-substituted allenoate provided access an all-carbon quaternary stereogenic center with complete diastereoselectivity. The observed relative stereochemistry can be explained using a Zimmerman-Traxler transition state model. Generality studies as well as experiments aimed at further clarifying this aldol mechanism will also be presented.

Titanium-mediated diastereoselective halo-aldol reactions resulting in α-vinyl β-hydroxy esters

255th National Meeting (2018)

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