Vinyl Ethers Containing an Epoxy Group:XXII.* Synthesis and Base-Catalyzed Transformations of 1-(Allyloxy)-and 1-[2-(Vinyloxy)ethoxy]-3-(2-propynyl-oxy)propan-2-ols

摘要

Reactions of 2-(allyloxymethyl)-and 2-[2-(vinyloxy)ethoxy]methyloxiranes with 2-propynol(approx3 wt % of t-BuOK,75-85 deg C,5-10 h)lead to formation of new 1-organyloxy-3-(2-propynyloxy)propan-2-ols(yield 65-95%).On heating to 45-100 deg C in the presence of bases(KOH,t-BuOK),1-allyloxy-and 1-[2-(vinyl-oxy)ethoxy]-3-(2-propynyloxy)propan-2-ols are transformed into the corresponding 2-vinyl-l,3-dioxolane,6-methyl-2,3-dihydro-1,4-dioxine,6-methylene-1,4-dioxane,and 2,3-dihydro-5H-1,4-dioxepine derivatives,whose yield and ratio strongly depend on the solvent nature,catalyst,and substituent at the hydroxy group.2-Vinyl-1,3-dioxolane and 6-methyl-2,3-dihydro-1,4-dioxine derivatives are formed as the major products(yield 70-99%)in the presence of t-BuOK in aprotic media(toluene,THF,DMSO)or in the absence of a solvent as a result of prototropic isomerization followed by intramolecular heterocyclization.Intramolecular nucleophilic cyclization of 3-(2-propynyloxy)propan-2-ols to 6-methylene-1,4-dioxane is the predominant process in water in the presence of KOH.In all cases,the fraction of 2,3-dihydro-5H-1,4-dioxepine derivatives among the cyclization products ranges from 0 to 5%(KOH)or to 14%(t-BuOK).