Synthesis of Tetrahydrofurans by Cyclization of Homoallylic Alcohols with Iodine/Iodine(III)

Tetrahydrofuran derivatives can be obtained by cyclofunctionalization of homoallylic alcohols bearing a terminal double bound by using [hydroxy(tosyloxy)iodo]benzene (HTIB, Koser’s reagent) in the presence of a catalytic amount of I<sub>2</sub> (20 mol %) in MeOH under mild conditions. This transformation is an overall 5-<i>endo</i><i>-trig</i> cyclization, which occurs by two different pathways. The first is a 4-<i>exo</i>-<i>trig</i> cyclization followed by ring expansion, whereas the second is an electrophilic addition followed by a 5-<i>endo</i>-<i>tet</i> cyclization.