Mechanistically Guided Design of an Efficient and Enantioselective Aminocatalytic α-Chlorination of Aldehydes

The enantioselective aminocatalytic α-chlorination of aldehydes is a challenging reaction because of its tendency to proceed through neutral intermediates in unselective pathways. Herein we report the rational shift to a highly selective reaction pathway involving charged intermediates using hexafluoroisopropanol as solvent. This change in mechanism has enabled us to match and improve upon the yields and enantioselectivities displayed by previous methods while using cheaper aminocatalysts and chlorinating agents, 80–95% less amount of catalyst, convenient temperatures, and shorter reaction times.