[quantumnumber]

Hello everyone,

I was trying to solve an excercise and I'm not sure I did it well. It states that using the reactives as shown in the picture I attach, you get the product I (which is the product of a Darzens condensation), and asks you how could you modify the reaction conditions in order to get the product II instead of product I.

I thought this can be done making first a enolate equivalent of the ketone (such as Lithium enolate, or sylil enol ether) and then adding the α-haloester, so that you can alkylate. Is it right?

Thanks a lot!

[AlphaScent]

I feel like this is a difference in the order of reagents.

Adding the alpha-halo ester to base will form the enolate.  Then adding ketone gives epoxide.

If you add ketone to base then add halo ester to that enolate it would give the desired product.

This is what you said, but can you completely modify the reagents??

[quantumnumber]

I'm not sure, the formulation only says "How could you modify the reaction conditions in order to get the product II instead of product I?", so I guess so.

In any case, I just wanted to know If the reaction I proposed would work, and I think is the same idea as yours. So thank you! It helped a lot!

[AlphaScent]

Yea, that is the way you would do it.

[spirochete]

If you can modify the reagents I think the best way to do it would be to use a stronger base, like LDA, to quantitatively produce the enolate from cyclohexanone, first. I'm not sure if the order of addition with sodium hydroxide would work because sodium hydroxide plus cyclohexanone would produce an equilibrium with a relatively small amount of enolate.

So if by lithium enolate you mean use LDA, then I think you're on the right track. Silyl enol ether might work too I don't remember if they work for this. Either way you would change the ketone to something not electrophilic, so the Darzen reaction can't happen.