Question

Assume general laboratory reagents are available.
Which of the following sequences could synthesize the following compound from the indicated starting material:

• A. 1: Dissolved metal reduction 2: Carboxylation 3: Lindlar$H_2$
• B. 1: Na/ethanol 2: Carboxylation 3: Lindlar$H_2$
• C. 1: $NaB{H}_{4}inethanol$ 2: Carboxylation 3: Lindlar$H_2$
• D. 1: $NaN{H}_{2}inN{H}_3$ 2: $C{O}_2\text{followed by}$ $H_3{O}^{+}$ 3: Lindlar$H_2$

Answer 1

The correct option is D

1: $NaN{H}_{2}inN{H}_3$ 2: $C{O}_2\text{followed by}$ $H_3{O}^{+}$ 3: Lindlar$H_2$

First, the acidic hydrogen is removed using soda amide and then it is carboxylated followed by a workup.
The last step is the selective reduction of the triple bond in 2-butynoic acid by Lindlar Pd and Hydrogen to the product: