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Topic: Synthesis dilemma  (Read 3939 times)

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Offline chunli

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Synthesis dilemma
« on: January 05, 2012, 08:13:41 PM »
Please help me carry out the following synthesis. Thanks a lot in advance..

Offline orgopete

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Re: Synthesis dilemma
« Reply #1 on: January 06, 2012, 09:06:47 AM »
I would need some convincing this problem is not an error based upon the poster's past questions (for example, what reagents are needed to catalyze an aldol condensation of acetophenone).

None the less, the kinds of strategies that could work are cycloheptene to dialdehyde to aldol cyclization to methylcyclohexene to alcohol to product. There are other similar strategies, for example a Favorskii rearrangement, but this reaction is not present in many introductory textbooks. It also requires a lot of additional manipulations. The last method would opening a cyclopropanol (bicyclo[4.1.0]heptan-1-ol) to the methyl ketone. While this last reaction would give the methyl ketone directly, I don't foresee any simple route to the required cyclopropanol, especially as it requires functionalization of the beta carbon (photochem?)

There are other ring contraction schemes. If this problem is not an error, then I hope that simply outlining possible routes would reveal similar schemes or rather similar functional group exchanges to the final product.
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Offline discodermolide

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Re: Synthesis dilemma
« Reply #2 on: January 06, 2012, 12:07:56 PM »
I would need some convincing this problem is not an error based upon the poster's past questions (for example, what reagents are needed to catalyze an aldol condensation of acetophenone).

None the less, the kinds of strategies that could work are cycloheptene to dialdehyde to aldol cyclization to methylcyclohexene to alcohol to product. There are other similar strategies, for example a Favorskii rearrangement, but this reaction is not present in many introductory textbooks. It also requires a lot of additional manipulations. The last method would opening a cyclopropanol (bicyclo[4.1.0]heptan-1-ol) to the methyl ketone. While this last reaction would give the methyl ketone directly, I don't foresee any simple route to the required cyclopropanol, especially as it requires functionalization of the beta carbon (photochem?)

There are other ring contraction schemes. If this problem is not an error, then I hope that simply outlining possible routes would reveal similar schemes or rather similar functional group exchanges to the final product.

I must say your answer leaves me with more of a dilemma!
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Offline chunli

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Re: Synthesis dilemma
« Reply #3 on: January 06, 2012, 12:51:50 PM »
Orgopete, this problem is not an error. It is a legitimate question in one of my homework problems. Also I don't come up with these questions on my own , they are given to me and when I get stuck I post them here after trying them on my own.Also my past question where you mentioned "the posters questions were based on an error" well just to let you know , my instructor was able to provide me with marks which would not have been possible if it was an error question. My brain literally fused after reading your answer.

Offline orgopete

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Re: Synthesis dilemma
« Reply #4 on: January 06, 2012, 04:38:13 PM »
Orgopete, this problem is not an error. It is a legitimate question in one of my homework problems. Also I don't come up with these questions on my own , they are given to me and when I get stuck I post them here after trying them on my own.Also my past question where you mentioned "the posters questions were based on an error" well just to let you know , my instructor was able to provide me with marks which would not have been possible if it was an error question. My brain literally fused after reading your answer.


I understand what you are saying. If someone has a simple solution to this problem, then I will agree that I have erred. The point I was making is that it is difficult to make this transformation. If this was an advanced organic chemistry class, that might be a different matter.

When problems are posted, they lack context to anyone willing to suggest an answer. If this problem occurred in a discussion of enamine chemistry, then a more plausible problem might have been cyclohexanone to methylcyclohexanone or cycloheptanone to methylcycloheptanone. As written, it looks like an error. (Parenthetically, I was not immune to making errors in writing my problems. A frequent source was failure to edit from past copy and paste actions. I tried to counter the negative effect by offering points to students who could point out these errors.)

Given the nature of this problem and since this seems like an introductory chemistry class, I would tell my instructor that I had attempted to solve this problem, but I could not find any relevant chemistry in the book for this transformation, and ask for help on doing it. I am making a prediction, your instructor will tell you there was an error (just an opinion).
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Offline fledarmus

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Re: Synthesis dilemma
« Reply #5 on: January 06, 2012, 05:00:10 PM »
This might help, but I doubt if it is anything you would find in less than a graduate level class:

http://pubs.acs.org/doi/abs/10.1021/ja0033537

Good luck

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