Question 1

Which reagent is most appropriate for the reduction of an ester to a primary alcohol in the synthesis of intermediate E from compound A in the exam scheme?

Accepted Answer

$$ \mathrm{LiAlH_4,\ MeOH} $$

Question 2

In the transformation of a terminal alkyne to a protected alcohol (MOMO-protected), which sequence of reagents is most suitable?

Accepted Answer

$$ \mathrm{1) MOMCl,\ 2) NaH} $$

Question 3

What is the role of IBX in the synthetic sequence shown in the exam?

Accepted Answer

IBX acts as an oxidizing agent, converting alcohols to aldehydes or ketones.

Question 4

Which reagent is used to convert a primary alcohol to a mesylate in the synthesis of intermediate G?

Accepted Answer

$$ \mathrm{MsCl,\ Et_3N} $$

Question 5

In the exam’s synthetic sequence, which reagent is used for the selective removal of a silyl protecting group?

Accepted Answer

$$ \mathrm{TBAF,\ THF} $$

Question 6

Which of the following best describes the function of NaN$$_3 in $$the transformation from intermediate C to F?

Accepted Answer

It acts as a nucleophile, substituting a leaving group with an azide.

Question 7

What is the purpose of using $$\mathrm{H_2$, Pd/C} in $$the final steps of the synthetic sequence?

Accepted Answer

To reduce azides to amines.

Question 8

Which protecting group is removed by treatment with Ba(OH)$$_2 in $$the exam’s synthetic sequence?

Accepted Answer

Ester (lactone ring opening)

Question 9

In the context of the exam, what is the function of $$\mathrm{(MeO)_2POCH_2Li} in $$the synthesis of intermediate B?

Accepted Answer

It acts as a Wittig reagent for olefination.

Question 10

Which sequence correctly describes the conversion of a terminal alkyne to a protected alcohol (MOMO-protected) in the exam’s synthetic route?

Accepted Answer

$$ \mathrm{1) MOMCl,\ 2) NaH} $$

Question 11

A student attempts to oxidize a primary alcohol to an aldehyde using IBX in DMSO. What is the expected product?

Accepted Answer

An aldehyde

Question 12

Which of the following is the best explanation for using $$\mathrm{0.1N\ HCl,\ EtOH} in $$the final step of the exam’s synthetic sequence?

Accepted Answer

To remove a protecting group under acidic conditions.

Question 13

In the exam’s synthetic sequence, which step introduces an azide group into the molecule?

Accepted Answer

Treatment with NaN$$_3 in $$DMF

Question 14

Which of the following best describes the function of TBSCl in the synthetic sequence?

Accepted Answer

It is used to protect alcohols as silyl ethers.

Question 15

A student mistakenly uses NaBH$$_4$$ instead of LiAlH$$_4 to $$reduce an ester. What is the likely outcome?

Accepted Answer

The ester is not reduced; NaBH$$_4 is $$not strong enough.

Question 16

Which of the following steps would most likely result in the formation of a lactone ring in the synthetic sequence?

Accepted Answer

Esterification of a hydroxy acid

Question 17

In the exam’s synthetic sequence, which reagent is used to convert a hydroxyl group to a good leaving group for nucleophilic substitution?

Accepted Answer

$$ \mathrm{TsCl,\ pyridine} $$

Question 18

Which of the following best describes the role of Ba(OH)$$_2 in $$the exam’s synthetic sequence?

Accepted Answer

It is used for base-catalyzed hydrolysis of esters.

Question 19

A student needs to selectively remove a TBS protecting group without affecting other protecting groups. Which reagent should they use?

Accepted Answer

$$ \mathrm{TBAF,\ THF} $$

Organic Chemistry in Drug Synthesis: Multi-Step Synthesis and Reaction Mechanisms

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