Alcohols hydroxy group activation

Trimethylsilyl iodide converts alcohols to iodides. The disadvantage of this method is the expensive reagent, which is avoided if trimethylsilyl chloride and sodium iodide are used instead (equation 27). Trimethylsilyl polyphosphate (PPSE), which is prepared from hexamethyldisiloxane and phosphorus pentoxide, also activates alcoholic hydroxy groups for substitutions with iodide anions (equation 28). ... 

Esters from Carboxylic Acids and Alcohols via Hydroxy Group Activation (HGA)... 

Aldehydes and ketones are similar in their response to hydrogenation catalysis, and an ordering of catalyst activities usually applies to both functions. But the difference between aliphatic and aromatic carbonyls is marked, and preferred catalysts differ. In hydrogenation of aliphatic carbonyls, hydrogenolysis seldom occurs, unless special structural features are present, but with aryl carbonyls either reduction to the alcohol or loss of the hydroxy group can be achieved at will. 

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