Anti-Selective Aldol Reactions of Pentafluorosulfanylacetic Acid Esters with Aldehydes Mediated by Dicyclohexylchloroborane.

Aldol reactions of pentafluorosulfanyl (SF5)-substituted acetic acid esters with both aromatic and aliphatic aldehydes proceeded with excellent anti-diastereoselectivity and good to high yields using dicyclohexylchloroborane/triethylamine. This methodology enabled the synthesis of hitherto unknown α-SF5-β-hydroxy esters. Using a norephedrine-based auxiliary, high asymmetric induction was observed. The stereochemistry of products was assigned by NMR spectroscopy and proved by X-ray diffraction analysis. The intermediate enolate was identified as a highly unstable species.