Textbook Question
Complete the following multistep syntheses using tosylate formation as one of the steps. The optimum number of steps for each synthesis is shown.
(c)
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12. Alcohols, Ethers, Epoxides and Thiols
Leaving Group Conversions - Sulfonyl Chlorides
Multiple Choice
Which of the following syntheses would be best to make the given molecule?
A
B
C
D
Verified step by step guidance1
Identify the target molecule: The target molecule is a nitrile with a cyano group (CN) attached to a chiral center. The stereochemistry is important, as the CN group is on a wedge, indicating a specific configuration.
Consider the starting material: The starting material is an alcohol with the hydroxyl group (OH) on the same chiral center. The goal is to replace the OH group with a CN group while maintaining the stereochemistry.
Evaluate the first synthesis option: The first option involves using H2SO4 and heat, followed by NaCN in DMSO. This method likely involves dehydration to form an alkene, followed by nucleophilic addition of CN. However, this may not retain stereochemistry.
Evaluate the second synthesis option: The second option uses TsCl and NEt3 to convert the alcohol to a tosylate, followed by NaCN in DMSO. This method is likely to proceed via an SN2 mechanism, which inverts stereochemistry.
Evaluate the third synthesis option: The third option uses PBr3 to convert the alcohol to an alkyl bromide, followed by NaCN in DMSO. This method also proceeds via an SN2 mechanism, which inverts stereochemistry. Consider which method best retains or inverts the stereochemistry as needed.
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