Metal-Directed Stereochemical Switching in Carboxylic Acid Addition to gem -Difluoroallenes

Herein, we describe a metal-directed approach to the stereodivergent hydrocarboxylation of gem -difluoroallenes (DFAs) with carboxylic acids, providing access to both Z - and E -alkenes bearing difluoromethyl ester substituents in high yields and with high levels of stereocontrol. The gem -difluoro substituents in DFAs play a pivotal role in governing the observed regioselectivity, while stereodivergence is dictated by the metal catalyst: a Ru-complex gives a Z -alkene, whereas a Pd-complex furnishes an E -alkene. Control experiments and DFT studies reveal that distinct catalytic pathways are responsible for the stereochemical divergence, with Ru-catalysis governed by electronic effects and Pd-catalysis dominated by entropic contributions to stereocontrol. This strategy provides a versatile approach to access stereodefined fluorinated building blocks that have potential downstream applications.