Hydroxyselenylation and Tethered Silanoxyselenylation of Allylic Silanols

We present protocols for the highly regioselective hydroxyselenylation and silanoxyselenylation of allylic silanols. N-(Phenylseleno)phthalimide acts as the selenylating agent for both transformations. Under basic conditions, hydroxyselenylation proceeds with >20:1 regioselectivity, and the products are valuable synthons for further transformations. We show that the silanol plays a critical role in maintaining the yield and regioselectivity of this reaction. Surprisingly, under acidic conditions, the hydroxyselenylation pathway is blocked, and products of a tethered silanoxyselenylation are exclusive.