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Topic: 2 Synthesis Problems.  (Read 7277 times)

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madisonwi

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2 Synthesis Problems.
« on: April 07, 2005, 10:20:30 AM »
Hello -

I have two syntheses that I have attempted, but I am unsure of their correctness.  In the Prob_Syn_23, I don't know if bromine will attach para.  In Prob_Syn_24, I am unsure if the bridge is correctly setup.

Thanks for any help.
madisonwi
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madisonwi

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Re:2 Synthesis Problems.
« Reply #1 on: April 07, 2005, 10:23:18 AM »
Other synthesis.
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Offline Donaldson Tan

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Re:2 Synthesis Problems.
« Reply #2 on: April 07, 2005, 08:24:48 PM »
bromine is ortho-para directing.
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GCT

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Re:2 Synthesis Problems.
« Reply #3 on: April 07, 2005, 09:11:19 PM »
For the first, I'm not quite sure if the grinard reagent will work too well with the hydroxyl group present, it might react acid/base fashion.  As far as the bromine attachment goes, I imagine that the hydroxyl carbon will be somewhat electron deficient...not sure if'll work too well.  Although it in reality it'll probably not effect the reaction too much.
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GCT

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Re:2 Synthesis Problems.
« Reply #4 on: April 07, 2005, 09:12:16 PM »
I'm not able to read your handwriting on the second proposal
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Offline hmx9123

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Re:2 Synthesis Problems.
« Reply #5 on: April 08, 2005, 12:37:02 AM »
You will wind up destroying the grignard with the alcohol there.  I would suggest protecting the alcohol, but that is probably beyond your course of synthesis at the present.  I guess my next question is why not add the isopropyl group first, perhaps by Friedel-Crafts alkylation, then continue with what you have?
« Last Edit: April 08, 2005, 01:16:57 AM by hmx9123 »
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Offline movies

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Re:2 Synthesis Problems.
« Reply #6 on: April 08, 2005, 06:20:42 PM »
Yeah, Grignard & alcohol are incompatible.

Also Freidel-Crafts type additions are generally not good with an alcohol in the molecule because the hydroxyl can complex your Lewis acid and prevent reaction.

In principle though, the alkyl group, even with the OH on it, should be ortho-para directing.  Usually para is favored based on sterics.
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Offline hmx9123

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Re:2 Synthesis Problems.
« Reply #7 on: April 09, 2005, 06:09:04 AM »
I should have been more specific.  Start the whole thing with F-C alkylation, then use the first posted step as step #2, and continue on from there.  The i-Pr group will be o-, p- directing, and since it's somewhat bulky, you may wind up with a bit more p- for when you add the bromine.  Then you continue on with the grignard, etc.
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Offline AWK

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Re:2 Synthesis Problems.
« Reply #8 on: April 11, 2005, 03:03:22 AM »
Protecting groups for alcohols:
http://www.swmed.edu/readylab/images/protecting%20groups.pdf

and some books:
Protective Groups in Organic Synthesis, 3rd edition (1999) by Theodora W. Greene and Peter G. M. Wuts
Protecting Groups, 3rd edition (2003)" by Philip Kocienski.
They can be find in university libraries.
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