A density functional theory study of the Sc^III-catalyzed asymmetric homologation of ketones with diazo compounds unveils a novel substrate coordination mode driven by the trans influence of counterions. This sheds light on the origins of the stereoselectivity and suggests a new strategy for adjusting it. More information can be found in the Research Article by M. Huang, Y.-D. Wu, and X. Zhang (DOI: 10.1002/chem.202303873).