Selectivity of dehydrogenative silicone–oxygen bond formation in diphenylsilane by base and base‐activated catalysts

Abstract

AbstractVarious base catalysts and base‐activated catalysts were evaluated for their steric inhibitions and selectivity in silicon–oxygen bond formation between hydroxyl groups and each of the two active hydrogen sites of diphenylsilane. Three hydroxides, six amines, and an organic‐soluble N‐heterocyclic carbene‐copper alkoxide complex (CuIPr‐NHC) were reviewed using in situ FTIR monitoring of reaction progress for the stepwise consumption of both Si–H bonds in diphenylsilane in the presence of water and various alcohols. Hydroxide catalysts with sodium, potassium, and tetramethylammonium (TMA) cations showed strong dependence of cation identity on reaction rate and observable rate order but did not lead to accumulation of a once‐oxidized silane. Amine catalysts exhibited varying levels of selectivity to the once oxidized silane, leading to accumulation of diphenylsilanol and hydride terminated oligomers with relative reaction rates seemingly dependent on the size of amine's alkyl substituents. CuIPr‐NHC showed very limited reactivity to the second dehydrogenation step in comparison to the first, leading to high accumulation of once‐oxidized silane. Leveraging this, the production of diphenyl(monoalkoxy)silanes has been demonstrated with representative primary, secondary, and tertiary alcohols.