Selective reduction of formamides to O-silylated hemiaminals or methylamines with HSiMe2Ph catalyzed by iridium complexes

Abstract

The reaction of (4-methyl-pyridin-2-iloxy)ditertbutylsilane (NSi^tBu–H, 1) with [IrCl(coe)₂]₂ affords the iridium(III) complex [Ir(H)(Cl)(κ²-NSi^tBu)(coe)] (2), which has been fully characterized including X-ray diffraction studies. The reaction of 2 with AgCF₃SO₃ leads to the formation of species [Ir(H)(CF₃SO₃)(κ²-NSi^tBu)(coe)] (3). The iridium complexes 2 and 3 are effective catalysts for the reduction of formamides with HSiMe₂Ph. The selectivity of the reduction process depends on the catalyst. Thus, by using complex 2, with a chloride ancillary ligand, it has been possible to selectively obtain the corresponding O-silylated hemiaminal by reaction of formamides with one equivalent of HSiMe₂Ph, while complex 3, with a triflate ligand instead of chloride, catalyzed the selective reduction of formamides to the corresponding methylamine.