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Author Topic: synthesis help  (Read 5149 times)

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Ak

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synthesis help
« on: August 07, 2008, 09:42:02 AM »

im working on a synthesis question my prof gave us, and ive been working on it and i keep hitting dead ends.  Ive tried retrosynthesis a lot of times but still nothing. I havent given up on it yet but i think i need a prod in the right direction.  So if someone can give me a hint it would be greatly appreciated.

And im only allowed to do a given reaction once.  And since this is an introduction course i havent learned tht many types of reactions...but i have learned reactions of alcohols, carboxylic acids, carboxylic acid derivatives, ketones, aldehydes, just the basic stuff.  Thanks
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azmanam

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Re: synthesis help
« Reply #1 on: August 07, 2008, 10:08:51 AM »

Are those really two aldehyde groups?

A product looking like that screams pericyclic reaction to me.  But for the life of me I can't find one that makes sense. 

Double check that you wrote the problem down correctly?  Typically instructors will pick a short synthesis from recent or classic literature.  That dialdehyde doesn't even show up in SciFinder, which makes me think something doesn't smell right.
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Ak

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Re: synthesis help
« Reply #2 on: August 07, 2008, 11:50:12 AM »

he gave us the question online and i copied and pasted it directly as it is...he says he always makes up his own questions and never repeats the same ones.
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Ak

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Re: synthesis help
« Reply #3 on: August 08, 2008, 09:33:20 AM »

i took another crack at it today and was able to retrosynthesis it till here (attachment)...now i cant get it from here (attachment) to the original material (see first post).  I know it mite seem easy but ive used some reactions already and as ive already said i can only use a give reaction only once.  Thanks

« Last Edit: August 08, 2008, 09:57:52 AM by Ak »
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azmanam

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Re: synthesis help
« Reply #4 on: August 08, 2008, 09:41:54 AM »

I don't see an attachment...
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Ak

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Re: synthesis help
« Reply #5 on: August 08, 2008, 09:56:18 AM »

lol i forgot to attach it...its now attached and the reactions i have used so far are:

- grignard
- alcohol to aldehyde by LiAlH4
- alcohol to aldehyde by NaBH4
- carboxylic acid to alochol
- nitrile to carboxylic acid
- alkyl halide to nitrile
- ozonolysis to make aldehydes
- H3O for dehydration of alcohol
- NBS to make allyic bromide
- and wittig reaction
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azmanam

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Re: synthesis help
« Reply #6 on: August 08, 2008, 10:04:45 AM »

I can get there in 6 steps from the starting material.  phenylselenenyl chloride is the key.  I won't go into too much more detail because it looks like this is for an assignment.

http://www.sigmaaldrich.com/catalog/search/ProductDetail/ALDRICH/183342
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azmanam

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Re: synthesis help
« Reply #7 on: August 08, 2008, 10:06:42 AM »

My 6 steps are not listed in your steps, so that's a good sign.

Do you mean aldehyde to alcohol by reaction with the hydride reagent?
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Ak

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Re: synthesis help
« Reply #8 on: August 08, 2008, 10:44:22 AM »

yeah it is for an assignment thts why ive been trying to do it myself, i just need a little help in the last few steps to get back to the starting material....i cant use your method because i havent learned about phenylselenenyl chloride...and i messed up at a part in my retro synthesis...forget the alcohol to aldehdye it should be:
- alcohol to aldehyde by PCC
- carboxylic acid to ester
- ester to aldehyde

but neways i need some help in the last part i need to know how i can form tht double bond.  thanks
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