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Topic: Does this work?  (Read 71771 times)

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Offline discodermolide

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Re: Does this work?
« Reply #135 on: April 02, 2013, 02:17:58 AM »
It does not make sense.
a) perhaps you did not form your amine.
b) perhaps the thioketene did not form
c) try heating it to 70°C to confirm your theory
d) Check the structures of all your intermediates, H-NMR, MS etc on pure materials.
e) Try trapping the thioketene with something you know works.
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Offline Messi

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Re: Does this work?
« Reply #136 on: April 02, 2013, 02:23:30 AM »
It does not make sense.

What does not make sense? My argument, or my reaction not working? Or both?  :-[

c) try heating it to 70°C to confirm your theory

My thioketene does not form at 70°C. I tried it.

Offline discodermolide

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Re: Does this work?
« Reply #137 on: April 02, 2013, 02:31:24 AM »
The reaction not working.
This may suggest that you do not have the structures you think you have.
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Offline Messi

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Re: Does this work?
« Reply #138 on: April 02, 2013, 02:37:11 AM »
But is my argument reasonable? I am very curious what you think as your knowledge of organic chemistry (in my eyes) is AMAZING!

1) Thioketene generation occurs best at -78°C. So once I create my thioketene I trap it with an amine to create the corresponding thioamide.

2) I would like to create a thiolactam, so I undergo the reaction intramolecularly with an amine functionality at -78°C and find that my thiolactam is not produced.

3) I realize that this might be a thermodynamic problem. Most of the time heat is required for cyclization. (NOT SURE IF THIS IS VALID POINT)

4) I decide to do the cyclization reaction at 70°C and there is no reaction.

5) I decide to go back to step 1) and generate a thioketene at 70°C and react it with an amine to create a thioamide... no reaction.

6) My final argument is that in order to create a thiolactam, heat is required, and because thioketenes are best generated at -78°C, the creation of a thiolactam is not possible in this way. A different method must be taken where the generation of a thioketene be done at higher temperatures.

Thoughts on this argument?

Offline discodermolide

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Re: Does this work?
« Reply #139 on: April 02, 2013, 02:51:39 AM »
OK, you know the reaction works with an amine to give the thioamide. Perhaps the aniline was not the best choice for this reaction. why not use the normal amine without the aromatic ring.
S=C=CCCCN

If that does not produce the lactam then you can say a different method must be employed to generate thioketenes when they are going to be used to form lactams.
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Offline Messi

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Re: Does this work?
« Reply #140 on: April 02, 2013, 02:55:02 AM »
OK, you know the reaction works with an amine to give the thioamide. Perhaps the aniline was not the best choice for this reaction. why not use the normal amine without the aromatic ring.

Yes, I've tried hexylamine as well and no luck! Oh, the joys of science!

I just hope my heat argument holds up in court... or my supervisor will kill me  :( As long as you think my argument is reasonable... I will be able to sleep well tonight. If not... well...  :'(

Offline discodermolide

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Re: Does this work?
« Reply #141 on: April 02, 2013, 02:57:09 AM »
In that case you can use your argument that thioketene to thiolactam cannot be done this way.
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Offline Messi

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Re: Does this work?
« Reply #142 on: April 02, 2013, 03:02:16 AM »
In that case you can use your argument that thioketene to thiolactam cannot be done this way.

Thank you discodermolide for all the help; I truly appreciate it. Hopefully all ends well, and my supervisor does not think I am a doofus because I am using heat as an argument. Also, I hope I don't get a poor mark because my research was unsuccessful and my arguments flawed. Only time will tell, and I thank you discodermolide for all the help. God bless you.

Offline discodermolide

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Re: Does this work?
« Reply #143 on: April 02, 2013, 03:03:59 AM »
My pleasure, sorry I could not get your reaction to work.
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Offline orgopete

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Re: Does this work?
« Reply #144 on: April 02, 2013, 09:16:36 AM »

1) Thioketene generation occurs best at -78°C.

Thoughts on this argument?

Occurs best? This is the step I am most skeptical of. I know the reaction to prepare a thioketene was performed, but are you sure you have a thioketene?
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Offline Messi

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Re: Does this work?
« Reply #145 on: April 02, 2013, 04:18:23 PM »
Occurs best? This is the step I am most skeptical of. I know the reaction to prepare a thioketene was performed, but are you sure you have a thioketene?

Yes, from literature, forming a thioketene is done in such a matter. I have confirmed with the trapping of an amine that I have indeed formed the thioketene. NMR data confirms this.

Offline orgopete

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Re: Does this work?
« Reply #146 on: April 04, 2013, 09:05:42 AM »
But is my argument reasonable? I am very curious what you think as your knowledge of organic chemistry (in my eyes) is AMAZING!

1) Thioketene generation occurs best at -78°C. So once I create my thioketene I trap it with an amine to create the corresponding thioamide.

2) I would like to create a thiolactam, so I undergo the reaction intramolecularly with an amine functionality at -78°C and find that my thiolactam is not produced.

3) I realize that this might be a thermodynamic problem. Most of the time heat is required for cyclization. (NOT SURE IF THIS IS VALID POINT)

4) I decide to do the cyclization reaction at 70°C and there is no reaction.

5) I decide to go back to step 1) and generate a thioketene at 70°C and react it with an amine to create a thioamide... no reaction.

6) My final argument is that in order to create a thiolactam, heat is required, and because thioketenes are best generated at -78°C, the creation of a thiolactam is not possible in this way. A different method must be taken where the generation of a thioketene be done at higher temperatures.

Thoughts on this argument?

I don't know what was or wasn't done. If you know a thioketene reacts with an amine to give a thioamide AND the above sequence of reactions does not give a thioamide, from my general knowledge and examining what appears to have been done, I was skeptical of the thioketene formation.

I've done some of these sulfur reactions and have found they can be very messy. Some of the prior descriptions appeared as though there was doubt about the thioketene, but the reaction was carried forward, but to failure. For me, ths is a red flag.
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Offline Messi

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Re: Does this work?
« Reply #147 on: April 06, 2013, 09:21:11 PM »
Good points orgopete. I thought of a further points below. Tell me what you think.

A problem may also be that not only the acetylide, but also the amino N may break up the S8 rings and possibly give some weird species with S-N bonds. So intermediate protection of the N may be helpful, e. g. bei silylation.

Maybe this is the solution! :D

Offline Messi

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Re: Does this work?
« Reply #148 on: April 11, 2013, 08:25:36 PM »
What do you think of this possible reaction scheme? Is it feasible? Would it work? :)


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