Protection of Diols as Acetals

Reductive cleavage of sulfonates with reducing agents may proceed either via C-0 or 0-S cleavage leading to alkanes and alcohols, respectively. For example, reduction of primary mesylates or tosylates with LAH furnishes preferentially the corresponding alkanes.  

For the more hindered secondary tosylates, hydride attack may occur at sulfur, 

Reduction of primary as well as secondary tosylates with LiEtjBH (Superhydride) provides a convenient method for the deoxygenation of alcohols to the corresponding 

Acetalization of 1,2- and 1,3-diols plays an important role in manipulating the reactivity of cyclic and acyclic polyhydroxy compounds. Acetals derived from 1,2- and 1,3-diols are readily accessible via their reactions with ketones or aldehydes in the presence of an acid catalyst. Once they are formed, acetals are very stable to basic conditions but are labile toward acids. 

The equilibrium of diol acetalization is shifted to the acetal side by removing the H2O. This may be accomplished by 

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