Copper Catalyzed Defluoroarylation of gem-Difluoroallenes to Allenyl Monofluorides with Aryl Boronic Esters.

Few studies have been performed on allenyl monofluorides, especially on aryl-substituted frames, due to concerns about their stability. Here we report a copper-catalyzed regioselective synthesis of such structures with inexpensive and accessible aryl boronic esters under mild conditions. Arylated allenyl monofluorides were stable enough to be isolated and easily converted to various other fluorine-containing blueprints. Preliminary asymmetric attempts demonstrate that the reaction could proceed via a selective ß-fluorine elimination process.

Enantioselective Assembly of Ferrocenes with Axial and Planar Chiralities via Palladium/Chiral Norbornene Cooperative Catalysis.

The preparation of ferrocenes with both axial and planar chiralities poses a considerable challenge. Herein, we report a strategy for the construction of both axial and planar chiralities in a ferrocene system via palladium/chiral norbornene (Pd/NBE*) cooperative catalysis. In this domino reaction, the first established axial chirality is dictated by Pd/NBE* cooperative catalysis, while the latter planar chirality is controlled by the preinstalled axial chirality through a unique axial-to-planar diastereoinduction process. This method exploits readily available ortho-ferrocene-tethered aryl iodides (16 examples) and the bulky 2,6-disubstituted aryl bromides (14 examples) as the starting materials. Five- to seven-membered benzo-fused ferrocenes with both axial and planar chiralities (32 examples) are obtained in one step with constantly high enantioselectivities (>99% e.e.) and diastereoselectivities (>19:1 d.r.).

Nickel-catalyzed reductive defluorination of iodo allylic gem-difluorides: allenyl monofluoride synthesis.

As a potential fluorinated synthon, there have been only limited reports on fluorinated allene synthesis and applications due to concerns about their stability. Here, we developed a nickel-catalyzed reductive defluorination of iodo allyl gem-difluorides to afford allenyl monofluorides under mild conditions with good functional group tolerance, which were easily converted to other C-F bond compounds, such as alkyl and alkenyl fluorides. Preliminary mechanistic studies suggested that monofluoroallenes were yielded by ß-F elimination of the alkenyl C-Ni intermediates from the oxidative addition of C-I bonds to a nickel(0) catalyst, while zinc regenerates the catalyst and closes the catalytic cycle.