(TsOH) as catalyst. . Check your organic textbook for the mechanism addition of alcohol to aldehydes or ketones to form acetals or ketals. The ketone carbonyl, significantly more reactive than the ester carbonyl, will react more rapidly with the ethylene glycol. Formation of the ketal involves an equilibrium in which water is one of the products. The equilibrium can be shifted to favor the product by removing the water as it is formed (Le Chatelier's principle). A Dean-Stark apparatus is used to accomplish this. See glassware appendix for an illustration of this apparatus.
Step2 - Grignard addition to the ester.
Once the reactive ketone moiety has been protected, the less reactive ester group can be modified. The ester is reduced by a Grignard reaction using phenylmagnesium bromide to produce the corresponding tertiary alcohol (2).
Step3 - Deprotection of ketone.
Removal of the ketal protecting group by hydrolysis with acid produces keto-alcohol (3). The ketone functionality is restored to the molecule now because the ketone will not react during the last step of the sequence (step 4 below). The mechanism for deprotection is essentially the reverse of that for step 1.