Chemistry Ester to acid chloride transformation

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    Organic chemistry
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The discussion focuses on the transformation of esters to acid chlorides, comparing two synthesis methods: one base-catalyzed (A) and one acid-catalyzed (B). The base-catalyzed method is preferred because the acid-catalyzed method fails due to the instability of silyl ethers in acidic conditions, which can lead to the loss of the protecting group. Participants note that the pH sensitivity of silyl ethers is not commonly emphasized in textbooks, despite being a well-known fact. The consensus is that the acid-sensitive nature of the protecting group in method B undermines its effectiveness. Understanding the stability of protecting groups is crucial for successful synthesis in organic chemistry.
jolly_math
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Homework Statement
Which best accomplishes the following transformation?
Relevant Equations
ester to acid chloride
1712982333579.png


Here are 2 options:
A)
1712982413712.png
B)
1712982432602.png


For both syntheses, a protecting group is added to the alcohol, the ester is hydrolyzed to a carboxylic acid, then it is turned into an acid chloride using SOCl2. The difference is that A is base-catalyzed and B is acid-catalyzed.

The correct answer is A, but I don't understand why B doesn't work or is worse than A.

Thank you.
 
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Eons passed since I worked with these things, but quick googling for stability of silyl ethers seems to be suggesting it is pH dependent.
 
Borek said:
Eons passed since I worked with these things, but quick googling for stability of silyl ethers seems to be suggesting it is pH dependent.
I've never seen this in my textbook or the resources I've used so far though. Is this a commonly-known fact?
 
Even wiki states: "Reaction with acids (...) removes the silyl group when protection is no longer needed.", so my bet is yes, it is something quite well known.
 
This protection group is acid sensitive. Step 2 in B negates step 1.
 
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