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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Meter on April 24, 2021, 12:20:23 PM

Title: Reactivity of aldehydes vs ketones with ethylene glycol protecting groups?
Post by: Meter on April 24, 2021, 12:20:23 PM: Hello.

I know that aldehydes are significantly more reactive than ketones when it comes to nucleophilic addition reactions (and arguably other reactions, such as Wittig), but does this principle hold for the protection of the groups with ethylene glycol? It's of interest in molecules where there exists both an aldehyde and a ketone. Will one be more or less reactive and result in a significant major (protected) product?
Title: Re: Reactivity of aldehydes vs ketones with ethylene glycol protecting groups?
Post by: rolnor on April 24, 2021, 01:20:31 PM: I think you get a mixture, its probably difficult to say how much of each. Better just try it.
Title: Re: Reactivity of aldehydes vs ketones with ethylene glycol protecting groups?
Post by: Meter on April 24, 2021, 02:01:44 PM: Quote from: rolnor on April 24, 2021, 01:20:31 PM
I think you get a mixture, its probably difficult to say how much of each. Better just try it.
Okay. I was considering using it for synthesizing 2-hydroxycyclohexanone from cyclohexanone. Although, now that you're here, is there an easier way to do it?
Title: Re: Reactivity of aldehydes vs ketones with ethylene glycol protecting groups?
Post by: rolnor on April 24, 2021, 05:11:29 PM: You can buy the dimer from Aldrich but its expensive. You can search on Scifinder or Reaxys to find a good method, its not worth the time to make one.
Title: Re: Reactivity of aldehydes vs ketones with ethylene glycol protecting groups?
Post by: Meter on April 24, 2021, 06:16:12 PM: Quote from: rolnor on April 24, 2021, 05:11:29 PM
You can buy the dimer from Aldrich but its expensive. You can search on Scifinder or Reaxys to find a good method, its not worth the time to make one.
It's part of a theoretical exercise, so I don't need to synthesize it. But thanks.
Title: Re: Reactivity of aldehydes vs ketones with ethylene glycol protecting groups?
Post by: rolnor on April 25, 2021, 03:54:21 AM: OK, thats different. Maybe you can brominate in the 2-position and treat the bromide with silveroxide in THF/H2O?
Title: Re: Reactivity of aldehydes vs ketones with ethylene glycol protecting groups?
Post by: Meter on April 25, 2021, 06:31:14 AM: Quote from: rolnor on April 25, 2021, 03:54:21 AM
OK, thats different. Maybe you can brominate in the 2-position and treat the bromide with silveroxide in THF/H2O?
Haven't heard of that reaction, but I'm surprised it never occurred to me to brominate the alpha-carbon.
Title: Re: Reactivity of aldehydes vs ketones with ethylene glycol protecting groups?
Post by: rolnor on April 25, 2021, 02:17:57 PM: I am not sure the method is really good but as a possible way to make it its acceptable. To make large amount I would hydrogenate 1,2-cyclohexanedione, I think that could work really well. The dione is in its enol-form.
Title: Re: Reactivity of aldehydes vs ketones with ethylene glycol protecting groups?
Post by: Meter on April 25, 2021, 02:27:56 PM: Quote from: rolnor on April 25, 2021, 02:17:57 PM
I am not sure the method is really good but as a possible way to make it its acceptable. To make large amount I would hydrogenate 1,2-cyclohexanedione, I think that could work really well. The dione is in its enol-form.
That seems to be a method from Reaxys as well, and I agree that it is a good idea.