Abstract
AbstractNew P‐stereogenic phosphoramidites based on a (–)‐pinane framework were synthesized and investigated by NMR spectroscopic methods and single‐crystal X‐ray structural analysis. The reaction between cis‐pinandiol 2 and N,N‐dialkylphosphoramidous dichlorides, followed by protection with theBH3·THF adduct, afforded diastereomeric mixtures of PS and PR BH3–phosphoramidite complexes. After separation by column chromatography, these stereoisomers were obtained in a pure form. The BH3 group was further cleaved by treatment with Et2NH at elevated temperature and the obtained free phosphoramidite ligands were used for catalytic enantioselective conjugate addition reactions. As substrates, a series of cyclic and acyclic enones was employed and addition was carried out with Et2Zn in the presence of catalytic amounts of CuI thiophenecarboxylate (CuTC) and a phosphoramidite ligand. The results revealed that the configuration of the phosphorus center controls the configuration of the newly formed stereogenic center of the β‐alkylated ketones.
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