A joint experimental and ab initio study on the reactivity of several hydroxy selenides. Stereoselective synthesis of cis-disubstituted tetrahydrofurans via seleniranium ions

The reactivity of several hydroxy selenides bearing an ethereal chain with catalytic amounts of perchloric acid in dichloromethane was investigated. Results showed that the position of the oxygen atom with respect to the seleniranium ring was crucial in order to get a good yield of the cyclized product. The factors on which yields of the 5-endo cyclization of the seleniranium ions depend were analysed by ab initio (HF/3-21G∗) studies. An explanation of the different coordinating ability, towards the positively charged selenium atom, of the allylic OMe and homoallylic OH-2 groups was given.