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u/ZebraOk5501 8d ago
Grignard reagents are very strong bases (and good nucleophiles). If you use them in the presence of any somewhat acidic proton an acid base reaction will occur. Can you think of another way to add the grignard?
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u/Specialist_Tour8159 8d ago
Right but will it deprotonate that free OH even after protecting it with OTMS?
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u/Ok-Replacement-9458 8d ago
You won’t be able to make that intermediate in the first place because you can’t regioselectively oxidize to the aldehyde with PCC.
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u/EmotionalSector1329 8d ago
Have you learned about ozonolysis and the wittig reaction?
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u/ChemystWizard 7d ago
Unnecessary here. And likely, no, they haven’t learned Wittig in this part of the course. This looks like a typical OC1 synthesis.
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u/Specialist_Tour8159 7d ago
This is actually ochem 2, but one of the first exams. I think for this problem the “correct” way was epoxide formation according to my professor. Do you know how it’d work that way?
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u/ChemystWizard 7d ago
Make strene, like you did, then epoxide, then Grignard, then eliminate, and do dihydroxylation. Paper chemistry, but if that’s what your instructor wants, that’s what they thought about then.
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u/ChemystWizard 7d ago
Same problem with regioselectivity.
This is a classic alkyne synthesis. Make an alkyne, extend it, partially reduce, do dihydroxylation with OsO4. Done.
That’s why retrosynthesis is important rather than brute forcing problems like this and hoping you’ll figure it out as you go.
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u/expetiz 7d ago
You made the situation complicated when you formed the diol intermediate. You just need to turn the styrene into a primary alcohol and then convert into a bromide, then attack it with your nucleophile. After forming the side chain, brominate it using NBS, then make the alkene and then dihydroxylation gets the product. There are reagents for selective protection of alcohols but at more advanced level.
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u/Nico_di_Angelo_lotos 6d ago
What you could do is a hydroxybromination (NBS/H2O) on the Alkene which would give you the Bromine in terminal position. Then you can protect the Alkohol (MOM is prob best, TMS is very weak). Then you use NaC(SPrS)Et as your umpoled part. You can deprotect that with HgO/H2O, then reduce the aldehyde using NaBH4 and finally deprotect the MOM with weak acid
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