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Offline aldoxime_amine

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Give the mechanism
« on: May 07, 2009, 12:19:28 PM »
See the attached picture.

Offline Dolphinsiu

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Re: Give the mechanism
« Reply #1 on: May 08, 2009, 06:21:14 AM »
It seems the fused junction is single bond. Isn't it?

Offline aldoxime_amine

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Re: Give the mechanism
« Reply #2 on: May 09, 2009, 12:02:13 PM »
I don't know what you are asking, but I feel the figure is very clear.

Offline macman104

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Re: Give the mechanism
« Reply #3 on: May 09, 2009, 12:29:07 PM »
This is an incomplete thought, but maybe it'll jog something for you.

The first thing that I notice is that we are adding acid to t-butanol.  This is a really common way of creating isobutylene which can undergo aromatic substitution.  So I see the ortho position attacking the isobutylene (but realistically, I would expect the methyl's ortho position to be more favored).  This sets you up to create your bridge with everything in place, however, I'm not sure how to create that connection.

One thought...when the ring attacks the isobutylene, you're going to have to kick those electrons from the double bond somewhere, so maybe those can somehow attack the other alkyl chain, but there's nothing on it to attack...

Offline aldoxime_amine

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Re: Give the mechanism
« Reply #4 on: May 09, 2009, 12:42:08 PM »
Atleast that gives us a start, but yes, the connection doesn't seem plausible at the moment..

Offline aldoxime_amine

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Re: Give the mechanism
« Reply #5 on: May 09, 2009, 12:52:58 PM »
Maybe the resulting carbanion forces a hydride out of the isopropyl (a la cannizaro) but maybe it is too far-fetched..

Offline macman104

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Re: Give the mechanism
« Reply #6 on: May 09, 2009, 01:23:55 PM »
Maybe the resulting carbanion forces a hydride out of the isopropyl (a la cannizaro) but maybe it is too far-fetched..
I don't think you'll be kicking out a hydride from the alkyl chain.  Is there any context to this question?  Not necessarily in the question itself, but relating to anything you've been studying in a class or working on?  Anything to suggest what our next move may be?

We have the SM, sulfuric acid, t-butanol and some water available to make that connection.  We generate an anion, and what can it do?  The most obvious thing is to be neutralized by the acid, but that's not what happens...

Also, you're 100% sure you've copied it correctly, as in no halogens, leaving groups, or activators available to us on the isopropyl chain?


Offline azmanam

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Re: Give the mechanism
« Reply #7 on: May 09, 2009, 01:36:12 PM »
You've got to do a redox reaction under acid/base conditions.  The acid'll do the F.C. alkylation as has been mentioned, but protons wont' get you through the redox reaction.  I feel sufuric acid is going to have to act as an oxidant somewhere.
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Offline azmanam

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Re: Give the mechanism
« Reply #8 on: May 09, 2009, 01:55:47 PM »
Got it.

The key lies in the hydride donor ability of aromatic hydrocarbons with tertiary, benzyllic hydrogens.  The resulting cation is sufficiently stable that hydride can be donated.

You also need a sacrificial equivalent of t-butanol.

Here are the relevant references:

http://dx.doi.org/10.1021/ja01186a038 (seems to be the seminal one people like to reference)
http://dx.doi.org/10.1021/jo00814a002
http://dx.doi.org/10.1139/v60-009

Knowing why you got a question wrong is better than knowing that you got a question right.

Offline aldoxime_amine

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Re: Give the mechanism
« Reply #9 on: May 10, 2009, 12:26:54 AM »
Got it.

The key lies in the hydride donor ability of aromatic hydrocarbons with tertiary, benzyllic hydrogens.  The resulting cation is sufficiently stable that hydride can be donated.

You also need a sacrificial equivalent of t-butanol.


Woohoo!! I guessed right, but having in mind a completely different reason  :P :P
I though there would be evolution of hydrogen gas, the hydride from the i-pr group combining with the acidic proton of sulfuric acid.

I've never seen a mechanism so strange, but I believe the question is not wrong as it is from a very reliable source.

Thanks, azmanam!
« Last Edit: May 10, 2009, 12:57:48 AM by aldoxime_amine »

Offline macman104

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Re: Give the mechanism
« Reply #10 on: May 10, 2009, 12:32:59 AM »
Just for curiosity sake Azmanam, what did you search for to find those references?  Or did you use some scifinder/drawing searches?

Offline azmanam

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Re: Give the mechanism
« Reply #11 on: May 10, 2009, 05:59:23 PM »
I started on Scifinder with drawing out the isopropyl benzene and the indene and doing a reaction search, and that only gave one reference for that type of indene formation.  It sent me to a patent (have I mentioned before how much I hate reading patent literature).  It didn't seem to have a mechanism.  Scifinder is always my first choice, so I wasn't hopeful.  But I tried Beilstein reaction search anyway... and got 160 reaction hits.  It whittled down to about 10 because most were from the same references. but it sent me to all of the above references.
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Offline macman104

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Re: Give the mechanism
« Reply #12 on: May 10, 2009, 06:01:44 PM »
I started on Scifinder with drawing out the isopropyl benzene and the indene and doing a reaction search, and that only gave one reference for that type of indene formation.  It sent me to a patent (have I mentioned before how much I hate reading patent literature).  It didn't seem to have a mechanism.  Scifinder is always my first choice, so I wasn't hopeful.  But I tried Beilstein reaction search anyway... and got 160 reaction hits.  It whittled down to about 10 because most were from the same references. but it sent me to all of the above references.
Thanks!

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