Aldehydes interconversion with acetals

Acetals hydrolyze under acidic conditions, but they are stable to strong bases and nucleophiles. Acetals areeasily made from the corresponding ketones and aldehydes and easily converted back to the parent carbonyl compounds. This easy interconversion makes acetals attractive as protecting groups to prevent ketones and aldehydes from reacting with strong bases and nucleophiles. 

Ketones/aldehydes, enols, and hemiacetals are all rapidly interconvertible under either acidic or basic conditions, but acetals and enol ethers are rapidly interconvertible with any of these species only under acidic conditions (Table 3.1). It is important for you to be able to recognize that any one of these species is functionally equivalent to any of the others under acidic conditions, and you need to be able to draw the mechanisms of their interconversion. 

Resolution of compounds containing functional groups that are not acidic or basic requires a reversible functional group interconversion involving a chiral resolving agent. For example, the reaction of a racemic alcohol with a chiral carboxylic acid results in a mixture of diastereomeric esters that can be separated. After separation, hydrolysis of the ester regenerates the desired alcohol. To resolve a racemic ketone or aldehyde, a reaction with a chiral diol or a chiral amine could be employed to form diastereomeric acetals or imines, respectively. 

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