Monitoring Reaction Intermediates to Predict Enantioselectivity Using Mass Spectrometry**

Enantioselective reactions are at the core of chemical synthesis. Their development mostly relies on prior knowledge, laborious product analysis and post-rationalization by theoretical methods. Here, we introduce a simple fast method to determine enantioselectivities based mass spectrometry. The is ion mobility separation diastereomeric intermediates, formed from chiral catalyst prochiral reactants, delayed reactant labeling experiments link spectra with reaction kinetics in solution. data provide rate constants along paths for individual revealing origins enantioselectivity. Using derived kinetics, enantioselectivity overall can be predicted. Hence, this offer rapid discovery optimization enantioselective future. We illustrate addition cyclopentadiene (CP) an α,β-unsaturated aldehyde catalyzed diarylprolinol silyl ether.