Our laboratory has a program of developing cyclization technology using the ditert-butyl silanol auxiliary (Scheme 1A). We have recently investigated the ring-opening of epoxides at varying distances from the pendant silanol tether. When the epoxide is located at carbons 4 and 5 relative to the silanol, silanoxytetrahydrofurans form from a tandem SN2 attack and silyl shift. We term this a [5,5]-mechanism, so named for the ring sizes involved in each step.