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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: zuriel on January 09, 2014, 06:56:39 AM

Title: Can anyone help me to name this rearrangement?
Post by: zuriel on January 09, 2014, 06:56:39 AM

Hey everyone,

I have a problem to work through and I'm stuck trying to think of the name of this particular rearrangement. I can work through the mechanism and product myself but I just need a little push with the name! I've looked through reaxys for a while now and can't get anywhere close to a similar reaction, and I feel somewhat dismayed.

Thanks for all help/advice in advance  :)

Title: Re: Can anyone help me to name this rearrangement?
Post by: zuriel on January 09, 2014, 08:30:19 AM

So from looking around some more I thought it might have been a Steven's Rearrangement but I'm still not 100% sure.

Title: Re: Can anyone help me to name this rearrangement?
Post by: AlphaScent on January 09, 2014, 09:57:58 AM

I honestly do not now this answer.  I will look at it carefully, but it is not Steven's.  The base that forms the ylid needs to have a hydrogen alpha to the amine salt.  That structure does not. 

Please post if you confirm an answer.

Title: Re: Can anyone help me to name this rearrangement?
Post by: discodermolide on January 09, 2014, 10:03:32 AM

What is your mechanism and product?

Title: Re: Can anyone help me to name this rearrangement?
Post by: zuriel on January 09, 2014, 01:27:51 PM

Hi everyone, I finally figured that this is a Dimroth Rearrangement. I'm going to work through the mechanism tomorrow and I'll post the solution then.  :)

Title: Re: Can anyone help me to name this rearrangement?
Post by: discodermolide on January 09, 2014, 02:28:55 PM

I thought that was with 4-amino-1,2,3 triazoles where the external nitrogen and a ring nitrogen switch positions?

Title: Re: Can anyone help me to name this rearrangement?
Post by: AlphaScent on January 09, 2014, 05:09:11 PM

It seems to be Disco is right.  I do not see the Dimroth mechanism following your posted reagents.  I could be wrong though.

http://en.wikipedia.org/wiki/Dimroth_rearrangement

Title: Re: Can anyone help me to name this rearrangement?
Post by: discodermolide on January 09, 2014, 05:12:19 PM

I would still like to see the product the OP is proposing and the mechanism. I have an idea as to what might be going on here.

Title: Re: Can anyone help me to name this rearrangement?
Post by: AlphaScent on January 10, 2014, 02:24:08 PM

I hope he does as well.  I do not know either.  Piperidine would make some more sense.  Possible Hoffman elimination.  The base throws me a bit.  I think it could be just written wrong.  We shall see.

Title: Re: Can anyone help me to name this rearrangement?
Post by: zuriel on January 11, 2014, 10:05:06 AM

Hey everyone, so the answer which was accepted in the seminar was in fact the Dimroth rearrangement. Here's the mechanism I drew out for it. Nucleophilic attack on methyl iodide sets the scene for a hydroxide to attack the intermediate structure. Once hydroxide attacks you get electrophilic ring opening and with the electron withdrawing nitro group in place, a resonant structure facilitates formation of a temporary single bond which allows the groups to switch. You then get ring closure and the N in the pyridine ring ends up being replaced with the N from the initial NH2!

Thanks everyone for your suggestions and input. If anyone would like me to draw out a more complete mechanism please let me know. And if anyone wants to consult the literature on this mechanism please see the Elsevier book 'Strategic Applications of Named Reactions in Organic Synthesis.'

(Also sorry if my handwriting isn't clear)

Title: Re: Can anyone help me to name this rearrangement?
Post by: AlphaScent on January 13, 2014, 10:17:25 AM

awesome.  Thank you.