RESUMO
This study presents an effective route to access functionalizable fluorinated enamides characterized by their high regiospecificity around the allenamide. Synthetic applications of the resulting difluorocarbonyl-bearing enamide products were pursued through straightforward synthetic transformations to prepare unknown functionalized valuable halogenated O-heterocycles and C5 skeletons. Experimental mechanistic studies showed that hydrodifluoroalkylation occurs via a hidden Brønsted acid activation, thereby establishing a new electrophilic activation mode for allenamide through a conjugated iminium intermediate.
RESUMO
The 1,1,1,3,3,3-hexafluoro-2-propanol-assisted allenamide activation enables metal-free regioselective intermolecular interception of amines, constituting a general C-N bond formation process for accessing value-added 1,3-diamines. Exclusive N-chemoselectivity (vs C for anilines) and regioselectivity were achieved for a broad range of substrates. Late-stage modification and further transformations of the 1,3-diamine products showcased the practicability and benefits of this strategy. Experimental mechanistic studies revealed that 1,1,1,3,3,3-hexafluoro-2-propanol mediates the proton transfer for activation of the allenamide. Density functional theory computations revealed the role of NaOAc in the formation of the reactive electrophilic intermediate, which ultimately governs the selective formation of the 1,3-diamine product.
