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Topic: Conversion  (Read 4374 times)

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Offline orgstudy

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Conversion
« on: April 06, 2011, 08:04:50 AM »
Hi all

I need help in following conversion (pic)

OH to be replaced by CH3 if X is highly deactivating

... i thought of treating with Zn and the Friedel craft ... but as benzene is highly deactivated so it wont work ... any help ???
Chemistry is a subject in which even the Professor can get confused at any time.

Offline Honclbrif

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Re: Conversion
« Reply #1 on: April 06, 2011, 09:16:43 AM »
Is that ring supposed to be a benzene?

Straight up replacing an -OH with anything is tricky. You will have to activate it first.
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Offline orgstudy

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Re: Conversion
« Reply #2 on: April 06, 2011, 12:47:23 PM »
Oh yes ... sorry ...  its benzene ... :D
Chemistry is a subject in which even the Professor can get confused at any time.

Offline jake.n

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Re: Conversion
« Reply #3 on: April 06, 2011, 03:36:49 PM »
I think Friedel-Craft makes sense for this reaction.  Even with the deactivators, you could force the reaction to completion as the EAS product of ipso attack eliminates water which will either condense or could be boiled out, depending on solvent system.

There may be a more efficient way to do it, but FC seems possible for this system if enough energy is added over a long enough period.

Offline orgstudy

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Re: Conversion
« Reply #4 on: April 06, 2011, 04:23:12 PM »
I told my teacher about FC but he said there is another better way ...
Chemistry is a subject in which even the Professor can get confused at any time.

Offline hobobot

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Re: Conversion
« Reply #5 on: April 06, 2011, 10:27:19 PM »
O-chem isn't my strong suit, but out of curiosity: why can't you just add HCl and do a SN2 type reaction? with the OH turning into an OH2+ and then the Cl- replacing it? Then FC becomes easier?

Offline Mikez

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Re: Conversion
« Reply #6 on: April 06, 2011, 10:49:40 PM »
this is perfect because since its deactivating the methyl will only be ADDED ONCE rather than multiple times

Offline nox

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Re: Conversion
« Reply #7 on: April 06, 2011, 11:36:15 PM »
This is a crazy idea, but thought I'd throw it out there:

1. Add triflic anhydride to make the phenyl triflate
2. Do a Suzuki coupling with methyl boronic acid


Offline jake.n

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Re: Conversion
« Reply #8 on: April 07, 2011, 12:32:15 AM »
I like Nox's Suzuki route.  I've attached another mechanism that looks like it would work conceptually.  Because this generates an intermediate dianion, I don't know how reasonable it really is, but the dianion should still be less basic than the Grignard reagent.


Offline Honclbrif

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Re: Conversion
« Reply #9 on: April 07, 2011, 11:32:34 AM »
@jake.n

I'm not crazy about the intermediate dianion either.

However, if the X's are pi-withdrawing (which I think is reasonable to assume since it is claimed they are "highly deactivating"), and the -OH is suitably activated, this is a great candidate for SNAr.
Individual results may vary

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