Ester to acid chloride transformation

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    Organic chemistry
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SUMMARY

The discussion focuses on the transformation of esters to acid chlorides using thionyl chloride (SOCl2) with two different catalytic approaches: base-catalyzed (Option A) and acid-catalyzed (Option B). Option A is identified as the correct method due to the stability of silyl ethers being pH dependent, which affects the protecting group used in the synthesis. The acid-catalyzed method (Option B) is deemed less effective because it compromises the protecting group established in the initial step, leading to a less favorable reaction outcome.

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  • Understanding of ester hydrolysis
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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.
 
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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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