TBAT-Catalyzed Dioxasilinane Formation from Beta-Hydroxy Ketones

Beta-hydroxy ketones can be converted to dioxasilinane products upon treatment with diphenylsilane and catalytic tetrabutylammonium difluorotriphenylsilicate (TBAT). These somewhat sensitive products could be isolated pure by column chromatography using florisil as the stationary phase. Alternatively, the dioxasilinane could be regioselectively opened with methyl lithium, affording the corresponding differentiated 1,3-diol with selective protection of the secondary alcohol as its diphenylmethylsilyl (DPMS) ether. A mechanism is proposed involving TBAT-catalyzed silyl ether formation followed by TBAT-promoted intramolecular carbonyl hydrosilylation. This mechanism is supported by the observed diastereoselectivity of the reaction, which was consistent with other carbonyl hydrosilylations thought to proceed intramolecularly.