LITHIATED 2-ALKYNYL-1,3-DIOXANES AS FULLY OXYGENATED ACYL-ANION EQUIVALENTS: SYNTHESIS OF 1-ALKYNYL KETONES

Article abstract of DOI:10.1016/S0040-4020(01)91548-0

2-Lithio-2-(trimethylsilylethynyl)-1,3-dioxane 3 is prepared from 2-(trimethylsilylethynyl)-1,3-dioxane with n-BuLi.Alkylation of 3 produces propargylic ketals 2 exclusively.Reaction with group IV-B chlorotrimethylmetalanes gives both propargylic products 2 and allenes 6 depending on the solvent used.Desilylation of 2 as well as hydrolysis to the alkynyl ketones 1 can be carried out under mild conditions.The first 1-alkynyl stannyl ketone has been prepared in this way.Formation of 2-lithio-2-(3,3-dimethyl-1-butynyl)-1,3-dioxane 10 requires t-BuLi.With various electrophiles 10 yields propargylic products and/or allenes in ratios depending on the solvent used.