Electrophilic 5-endo-trig cyclisations of 2-silyl-3-alkenols. A stereoselective route to polysubstituted tetrahydrofurans
摘要:
Electrophilic 5-endo-trig cyclisations of allylsilanes have been carried out leading to tri- and tetrasubstituted tetrahydrofurans with reasonable fields and excellent diastereoselectivities. A rationalization of both the regio- and the stereoselectivity has been proposed. A silicon group having a thienyl fragment attached to the silicon has also been devised was shown to be oxidized under both electrophilic and nucleophilic conditions. (C) 1997 Elsevier Science Ltd.
Mercury-desilylation of cyclopropylmethylsilanes affords a stereospecific access to homoallylic mercury intermediates, which can be elaborated further. This strategy is illustrated with a short access to carba-furanoses and carba-C-disaccharides.
5-endo-trig selenoetherifications of substituted 2-silyl-3-alkenols gave tri- or tetrasubstituted 2,4-cis tetrahydrofurans in moderate to good yields with excellent diastereoselectivities. Opposite stereoselectivities were found with an analogous allylic diol. A transition state model has been proposed to rationalize this stereochemical outcome.
Electrophilic 5-endo-trig cyclisations of allylsilanes have been carried out leading to tri- and tetrasubstituted tetrahydrofurans with reasonable fields and excellent diastereoselectivities. A rationalization of both the regio- and the stereoselectivity has been proposed. A silicon group having a thienyl fragment attached to the silicon has also been devised was shown to be oxidized under both electrophilic and nucleophilic conditions. (C) 1997 Elsevier Science Ltd.
Epoxidation and cyclopropanation of 2-silyl-3-alkenols. A study of 1,2-asymmetric induction
作者:Yannick Landais、Liliana Parra-Rapado
DOI:10.1016/0040-4039(95)02386-0
日期:1996.2
Epoxidation and cyclopropanation of 2-silyl-3-alkenols have been shown to occur with high 1,2-stereocontrol through substrate directable reactions. Both syn and anti epoxides are thus available from E and Z-allylsilanes. This contrasts with the results usually observed for allylsilanes lacking a coordinating group.