Stereospecific Rhodium-Catalyzed Addition of Carboxylic Acids to gem -Difluoroallenes: Access to cis -1,1-Difluoroallyl Esters

The gem -difluoroallylated scaffold holds a significant value in medicinal chemistry. However, stereoselective access to its cis -configured motif, thermodynamically disfavored over the trans isomer, remains a long-standing synthetic challenge. Herein, we report a rhodium(III)-catalyzed addition reaction of carboxylic acids to gem -difluoroallylations, which efficiently affords cis -1,1-difluoroallyl esters with high stereospecificity under ambient conditions. Mechanistic studies reveal that the bulky Cp*Rh(III) moiety dictates the stereochemical outcome via steric control during concerted difluoroallene coordination and carboxylate migration, where subsequent metal-centered protonation secures the exclusive cis configuration of the final gem -difluoroallylic products.