Catalytic Enantioselective Decarboxylative Cross‐Coupling of β‐Ketoacids With <i>gem</i> ‐Difluoroallenes Enabled by Fluorine‐Induced Allylrhodium Isomerization

Catalytic decarboxylative allylic alkylation (DAA) reaction represents an efficient strategy for synthesizing molecules containing both carbonyl and alkenyl functionalities, yet is frequently challenged by multiple selectivity issues. Here we report the first intermolecular decarboxylative cross-coupling of β-ketoacids with internal allenes. Using a Rh^(I)/(S,S)-Ph-BPE system, α-gem-difluoroallylic carbonyl compounds can be generated with excellent chemo-, regio-, and enantioselectivities. Mechanistic studies support "coordination-assisted inner-sphere addition-decarboxylation" pathway, where C─C bond formation occurs prior to the decarboxylation step. Fluorine-induced anti→syn isomerization of π-allyl-rhodium species proves to be the key factor governing the stereoselectivity of this reaction. This cross-coupling reaction tolerates a range of functional groups and advances the field of decarboxylative allylic alkylation.