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. R esults showed that the position of the oxygen atom with respect to the sele niranium ring was crucial in order to aet a good yield of the cyclized prod uct. The factors on which yields of the 5-endo cyclization of the seleniran ium ions depend were analysed by ab initio (HF/3-21G*) studies. An explanat ion of the different coordinating ability, towards the positively charged s elenium atom, of the allylic OMe and homoallylic OH-2 groups was given. (C) 2001 Elsevier Science Ltd. All rights reserved.