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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Rutherford on February 23, 2014, 05:21:44 AM

Title: Radical addition scheme
Post by: Rutherford on February 23, 2014, 05:21:44 AM
The problem is attached, I need to determine the unknown compounds. I will attach my attempt in the next post.

The whole problem can be found here http://icho2014.hus.edu.vn/Preparatory-Problems/0001/01/Preparatory-Problems-224.html it is the 23rd.
Title: Re: Radical addition scheme
Post by: Rutherford on February 23, 2014, 05:22:29 AM
What transformation will F undergo?
Title: Re: Radical addition scheme
Post by: discodermolide on February 23, 2014, 05:52:47 AM
What happens to the primary radical you formed by closing the ring. Is there not a substituent on that methyl group?
Title: Re: Radical addition scheme
Post by: Rutherford on February 23, 2014, 06:00:08 AM
What substituent?
Title: Re: Radical addition scheme
Post by: discodermolide on February 23, 2014, 06:02:28 AM
Do the radical cyclisation you end up with a primary radical, what happens to it?
Title: Re: Radical addition scheme
Post by: Rutherford on February 23, 2014, 06:02:42 AM
I forgot the radical on the methyl group, it will undergo a transformation with the azide, right? But where does the methyl on nitrogen come from?
Title: Re: Radical addition scheme
Post by: discodermolide on February 23, 2014, 06:08:27 AM
I don't think it reacts with the azide
Title: Re: Radical addition scheme
Post by: Rutherford on February 23, 2014, 06:22:32 AM
What else path could afford the final compound?
Title: Re: Radical addition scheme
Post by: discodermolide on February 23, 2014, 06:26:35 AM
If your compound F is correct, what could compound G be?, Compound G looses N2 after acid treatment. So F must be some sort of reactive intermediate that transforms to G, your F will not do anything.
Title: Re: Radical addition scheme
Post by: discodermolide on February 23, 2014, 06:29:10 AM
OK, you have a primary radical, lets say it reacts with the azide, what compound do you get?
Title: Re: Radical addition scheme
Post by: discodermolide on February 23, 2014, 06:33:14 AM
this compound
[C]C1(CCN=[N+]=[N-])C2=CC(OC)=CC=C2N(CC3=CC=CC=C3)C1=O

the thing the smiles had marked C(1) is supposed to be a radical
Title: Re: Radical addition scheme
Post by: Rutherford on February 23, 2014, 06:51:44 AM
The primary radical has to react with nitrogen, N2 will be released, so the final compound after treatment with CH3X would be obtained, I think. But I can't think of a mechanism for the reaction.
Title: Re: Radical addition scheme
Post by: discodermolide on February 23, 2014, 06:53:10 AM
No, do it stepwise:
Title: Re: Radical addition scheme
Post by: Rutherford on February 23, 2014, 06:58:54 AM
Then the lone pair from nitrogen will end up forming a triple bond, and the other N-N bond will be cleaved to form nitrogen molecule and a radical that will abstract a hydrogen to obtain I?
Title: Re: Radical addition scheme
Post by: discodermolide on February 23, 2014, 07:01:01 AM
more or less:
Title: Re: Radical addition scheme
Post by: Rutherford on February 23, 2014, 07:13:54 AM
One nitrogen in the nitrogen molecule would have 2- charge.
Title: Re: Radical addition scheme
Post by: discodermolide on February 23, 2014, 08:52:58 AM
you got the structure, you figure out the charges pls
Title: Re: Radical addition scheme
Post by: Rutherford on February 23, 2014, 09:18:25 AM
In the path you wrote. the nitrogen doesn't lose it's negative charge, so in the formed nitrogen molecule one nitrogen would be negative.
Title: Re: Radical addition scheme
Post by: discodermolide on February 23, 2014, 09:27:42 AM
Then in the drawing I forgot to change it.
Title: Re: Radical addition scheme
Post by: orgopete on February 23, 2014, 11:33:41 AM
I didn't know this right off, so I had to do some searching for some of the steps. I suggest you write out every single step. Then it might be helpful to draw the alternate form of the azide. I think the cyclization step may look different and the radical mediator mechanism will change. I don't think there is any Me3SiH forming.
Title: Re: Radical addition scheme
Post by: discodermolide on February 23, 2014, 12:07:01 PM
Thanks orgopete,
How do you see this proceeding?. There is a Google books reference to domino reactions, this is in there.
sorry for the long link
http://books.google.ch/books?id=HfdEud1Qvq0C&pg=PA229&lpg=PA229&dq=horsfiline+synthesis&source=bl&ots=7PPPMvUUwd&sig=VRI_o85y_Wm4GbOC1bXi5JE-p6c&hl=en&sa=X&ei=EtsJU-2mIOL_ygO33oHACw&ved=0CFwQ6AEwCjgK#v=onepage&q=horsfiline%20synthesis&f=false (http://books.google.ch/books?id=HfdEud1Qvq0C&pg=PA229&lpg=PA229&dq=horsfiline+synthesis&source=bl&ots=7PPPMvUUwd&sig=VRI_o85y_Wm4GbOC1bXi5JE-p6c&hl=en&sa=X&ei=EtsJU-2mIOL_ygO33oHACw&ved=0CFwQ6AEwCjgK#v=onepage&q=horsfiline%20synthesis&f=false)

I invoked the R3SiH to provide a source of the H radical after (during) the nitrogen elimination. So you end up with a radical initiator for the next reaction.
Title: Re: Radical addition scheme
Post by: Rutherford on February 23, 2014, 12:39:14 PM
I got this:
Title: Re: Radical addition scheme
Post by: discodermolide on February 23, 2014, 12:51:35 PM
That's OK, but where does the H radical come from?
Title: Re: Radical addition scheme
Post by: Rutherford on February 23, 2014, 02:17:27 PM
They gave above the reaction arrow: +H+ and -N2, although I think that it is a mistake and that it should be radical hydrogen.
Title: Re: Radical addition scheme
Post by: discodermolide on February 23, 2014, 02:31:21 PM
I think it comes from the silane.
Let's see if orgopete has a different source.
Title: Re: Radical addition scheme
Post by: orgopete on February 23, 2014, 08:19:51 PM
In the scheme, it was written as "+H+". Since the literature was using TTMSS, it showed a TMS on the nitrogen. This propagated the radical for cleaving the iodine and initiating the reaction. So I presume protonation was to cleave the silyl group. I didn't see any other hydrogen source. If a tin hydride were used, that would be different.