Control of hydroxyl group conformation by the pentafluorosulfanyl group

The unique properties of the pentafluorosulfanyl group lead to previously unrecognized interactions with neighboring hydroxyl groups that differ substantially from those of alkyl or fluoroalkyl chains. Computational methods (B3LYP/6-31++G(d,p)) were utilized to assess the geometries and barriers to rotation. Conformational control was derived primarily from restricted rotation about the SF5CCOH bond.

A computationally-driven comparison of the effects of fluorinated groups (SF5, CF3, CF2H and CFH2) with a sterically demanding tert-butyl group (tBu) on interactions with an adjacent α-hydroxymethylene groups was undertaken with the model structures shown below. The unique properties of the pentafluorosulfanyl group were found to lead to previously unrecognized interactions with neighboring hydroxyl groups that differ substantially from those commonly found with alkyl or fluoroalkyl chains.Figure optionsDownload as PowerPoint slideHighlights
► The effects of fluorinated groups (SF5, CF3, CF2H and CFH2) were compared.
► The SF5-substitution leads to large barrier to rotation about the SF5CCOH bond.
► RCCO and CS virtual orbitals influence the hydroxyl group conformation.