Host: Division of Organic Chemistry, The Pharmaceutical Society of Japan
The title acetal has been prepared from allyltriisopropylsilane in two steps in 60-75% yield. This acetal can react with 1,2- or 1,3-diols in the presence of acid catalyst to give the corresponding 1,3-dioxolane or 1,3-dioxane in excellent yields. The cyclic acetal is relatively stable under weak acidic conditions. For example, it survives in acetic acid at 80 °C or PPTS in organic solvents. This protecting group can be removed under mild conditions by the treatment of LiBF4 in acetonitrile to give the starting diol efficiently. However, it is hardly deprotected with tetrabutylammonium fluoride. In addition, HF/pyridine can use for the deprotection of 1,3-dioxolane derivatives but not 1,3-dioxane derivatives. Selective protection/deprotection for 1,2- and 1,3-diols can be achieved by the use of triisopropylsilylacetal. Particularly, tolerance of acetal to acids is valuable for organic synthesis.
