Heterocyclic synthesis by C-C bond formation. Tetrahydrofuran and tetrahydropyran synthesis via oxonium ion-mediated cyclisation reactions

Article abstract of DOI:10.1016/S0040-4039(97)10294-5

Dimethyl(methylthio)sulfonium tetrafluoroborate triggers ionisation and cyclisation of hemithioacetals 3 to give tetrahydrofurans 8-11 in good yields and stereoselectivities. The homologous sulfone analogues 17 give tetrahydropyrans on treatment with ethy