Allylic silanes bearing a silylmethyl group at the allylic position were prepared as both (E)-and (Z)-alkene stereoisomers. These compounds undergo reactions with aldehydes in the presence of Lewis acids to provide tetrahydrofurans, bearing up to five stereogenic centers, as single diastereomers. These annulation processes are likely facilitated because the reactions proceed via carbocations that are stabilized by two b-silyl substituents.