Conversion to aldehydes [LiAlH(OtBu)3]

Conversion to aldehydes [LiAlH(OtBu)3] Definition:

 

Addition of the bulky reducing reagent lithium tri-t-butoxy aluminum hydride [LiAlH(OtBu)3] to acid chlorides results in the formation of aldehydes.

 

 

Conversion to aldehydes [LiAlH(OtBu)3] Explained:

 

Similar to esters (reductions with LAH and DiBAl-H), aldehydes cannot be produced with common reagents for reduction, such as lithium aluminum hydride (LAH) and sodium borohydride. Using one equivalent of LAH simply leads to a mess of products. To prevent such overreduction, the LAH must be modified with three equivalent of 2-methyl-2-propanol (or tert-butyl alcohol). In this manner, three of the reactive hydride atoms will be neutralized, leaving one behind that is enough for reduction of acid chloride but not the resulting aldehyde.

 

 

The resulting modified LAH i.e. lithium-tri(tert-butoxy)aluminum-hydride can be used to reduce acyl chloride by the following mechanism: