Quaternary stereocenters: Chiral α-magnesiated nitriles can be formed by deprotonation and are configurationally stable at low temperature, even for acyclic examples. These can be trapped with electrophiles to give enantiomerically enriched quaternary substituted products.
Barker, G., Alshawish, M. R., Skilbeck, M. C., & Coldham, I. (2013). Remarkable Configurational Stability of Magnesiated Nitriles. Angewandte Chemie International Edition, 52(30), 7700-7703. https://doi.org/10.1002/anie.201303442