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Influence of β-Substituents in Aldol Reactions of Boron Enolates of β-Alkoxy Methylketones

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journal contribution
posted on 05.11.2010, 00:00 by Luiz C. Dias, Emílio C. de Lucca, Marco A. B. Ferreira, Danilo C. Garcia, Cláudio F. Tormena
Moderate to good levels of substrate-based 1,5-syn-stereocontrol could be achieved in the boron-mediated aldol reactions of β-tert-butyl methylketones with achiral aldehydes, independent of the nature of the β-alkoxy protecting group (P = PMB or TBS). The analysis of the relative energies of the transition structures by theoretical calculations using the density functional B3LYP shows relative energies favoring the corresponding OUT-1,5-SYN transition structures, explaining the observed 1,5-syn stereoinduction.