Hydrodefluorination of non-activated C-F bonds by diisobutyl-aluminiumhydride via the aluminium cation [i-Bu2Al]+

A novel system for the hydrodefluorination (HDF) of non-activated C-F bonds at room-temperature is described. The reaction of i-Bu2AlH with [Ph3C][B(C6F5)4] (1), [Ph3C][Al(C6F5)4] (2) and [Ph3C][Al{OC(CF3)3}4] (3) as precatalysts leads under formation of triphenylmethane to the aluminium cation [i-Bu2Al]+ and the non-coordinating anions [M(C6F5)4]− (M = B, Al) and [Al{OC(CF3)3}4]−. The formed aluminium cation is very reactive towards C-F bonds and easily forms i-Bu2AlF releasing a carbocation that abstracts the hydride of excess i-Bu2AlH and yields the corresponding hydrocarbon. Thereby, the active species [i-Bu2Al]+ is regenerated and can realize a catalytic cycle. For 1-fluorohexane as an example including non-activated C-F bonds different activities were found (TON: 1: 20; 2: 12; 3: 30) in cyclohexane as solvent.

Graphical abstractDownload full-size image