A novel oxidative cyclisation onto vinyl silanes.

A novel osmium-catalysed oxidative cyclisation of 1,2-diols bearing a pendant vinyl silane affords THFs that contain silicon functionality at the ring junction. When the cyclisation occurs onto a vinyl benzyldimethylsilyl group, the resulting silyl group can act as a masked hydroxyl group and undergo a Fleming-Tamao type oxidation at a later stage to form the corresponding lactol. The scope of this reaction can also be extended beyond 1,2-diols and applied to the cyclisation of α-hydroxy-sulfonamides and α-hydroxy-amides.