Study of the Configuration Stability of the Carbon – Zinc Bond, Direct Measurement of Enantiomeric Ratios, and Tentative Assignment of the Absolute Configuration in Secondary Organozinc Halides

A straightforward way to determine enantiomeric ratios and predict absolute configurations in organozinc reagents is possible by the use of (+)-2,2′-isopropylidene-bis((R)-4-phenyloxazoline) ((+)-1) and its racemic counterpart (±)-1 as chiral solvating agents for NMR spectroscopy. The signals corresponding to the α-hydrogen atom (relative to the zinc atom) in a secondary organozinc bromide and its evolution after chiral (left) and racemic (right) complexation are shown.