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Herein, we demonstrate the formation of monofluoroallenes through copper‐catalyzed defluoroalkylation or defluoroarylation of gem‐difluoroallenes using affordable and readily available Grignard reagents. Additionally, alkyl lithium or alkyl zinc reagents proved successful in these transformations. Under mild conditions, monofluoroallenes can be converted into fluorinated olefinic compounds or non‐fluorinated alkyne compounds. Initial mechanistic studies suggest that the reaction may start with an organocopper reagent and undergo a rapid β‐F elimination step. Although the current enantiomeric excess is low, chiral ligands could facilitate the asymmetric transformation of this reaction. [ABSTRACT FROM AUTHOR]

A rhodium-catalyzed protocol has been established for the enantioselective hydroamination of gem-difluoroallenes with anilines. This strategy shows complete atom-efficiency to access a variety of enantioenriched gem-difluoroallylic amines in excellent branched selectivity (>99:1 for each case), which are important backbones in many biologically active compounds. Mechanistic studies suggest the generation of a gem-difluoro π-allyl rhodium intermediate by an exclusive hydrometalation pathway, which undergoes nucleophilic substitution of amines.

Summary: Multi-functionalized tertiary/secondary boronates and silanes have found wide applications in areas spanning organic synthesis, advanced material development, and pharmaceutical research. Effective access to these versatile motifs via protoboration/silylation of allenes remains unfulfilled. Capitalizing on the fluorine effects, here we report copper-catalyzed protoboration/silylation of gem-difluoroallenes, which shows an abnormal reactivity profile. In stark contrast to the conventional paradigms of allene functionalization reactions, which are often subjected to the steric-control mode for more facile reaction initiation on lower-substituted double bonds, the present reaction displays a virtually reversed regioselectivity for the more sterically congested π system. The synergistic LUMO-lowering perturbation and stabilization of nascent organocopper by fluorine substituents are deemed critical for guaranteeing the high fidelity of the present transformation. We not only apply this developed methodology to the late-stage modification of compounds derived from natural products but also highlight the utility of the obtained gem-difluoroalkenes in further synthetic elaborations.