Question

Draw a stepwise mechanism for the following reaction. Your mechanism must show how both organic products are formed.

Short answer

Answer

The reaction takes place by protecting the carbonyl group and reducing ester to alcohol, followed by deprotection of the carbonyl group and alcohol reduction.

The Grignard reagent is used as a nucleophile.

Step-by-step solution

Step-by-Step Solution Step 1: Protection of carbonyl group

Ester reduction is required for the formation of alcohol. In the presence of carbonyl, the ester cannot be reduced. Therefore, protection of carbonyl is required. Once the ester is reduced, deprotection can be done to obtain carbonyl.

Step-wise mechanism

• Protection of the carbonyl group using ethylene glycol

Protection of carbonyl group

• Methyl magnesium bromide acts as a nucleophile and attacks on the ester’s carbonyl group to form alkoxide ion.

Attack of nucleophile

• The carbonyl group is reformed, and ketone is expelled as a leaving group followed by hydrolysis to give alcohol. The formed ketone reacts with another mole of methyl magnesium bromide and forms tert-butanol.

The departure of leaving group

• Deprotection of carbonyl group

Deprotection of carbonyl group

• The reaction of the carbonyl group with Grignard reagent and hydrolysis gives the desired product.

Reduction of carbonyl