[Nescafe]

Hello,

I am not how to name my product but I have made cholestan-3-one but instead of a carbonyl imagine an alkene, and then a nitrile at the terminal position. so basically NC-CH=CH-Cholesterol.

If I treat with pd/c under mild conditions to reduce the double bond, would you reckon to obtain only a single isomer taken into account that the cholesterol is more hindered on the top face (basically pd/c will add syn to the bottom face?). Or will it be a mixture of diastereomers?

Thanks in advance,

Nescafe.

[billnotgatez]

We do not double post here
I deleted your other copy
Please read forum rules again - you seem to have forgotten them

[Archer]

You'll get syn addition if that's what you mean.

It wouldn't matter if it wasn't though, saturating that double bond cannot form isomers.

Scribble the structure of this functionality, then scribble the hydrogenation products from syn and anti addition.

[Nescafe]

You'll get syn addition if that's what you mean.

It wouldn't matter if it wasn't though, saturating that double bond cannot form isomers.

Scribble the structure of this functionality, then scribble the hydrogenation products from syn and anti addition.

Thanks.

I understand that it is a syn addition, but I was under the impression that you form both R and S products? Since cholesterol has chiral centers how can it not matter?

[Nescafe]

You'll get syn addition if that's what you mean.

It wouldn't matter if it wasn't though, saturating that double bond cannot form isomers.

Scribble the structure of this functionality, then scribble the hydrogenation products from syn and anti addition.

I just realized I wrote my structure wrong. The structure is C≡N-CH=Cholesterol, I was expecting only one isomer but I think I am dealing with a 50:50 mixture, does this make sense?

[Archer]

Yes, you may have a mixture of isomers (what sort of isomers are these?) the ratio will be dependent on the method of synthesis you may have exclusively one isomer. Just to make sure we are agreed on the structure before we proceed



Is this correct? Is there definitely a CH₂ separating the olefin and the C≡N?


How did you prepare this product?

[Nescafe]

Yes, you may have a mixture of isomers (what sort of isomers are these?) the ratio will be dependent on the method of synthesis you may have exclusively one isomer. Just to make sure we are agreed on the structure before we proceed



Is this correct? Is there definitely a CH₂ separating the olefin and the C≡N?


How did you prepare this product?

thanks for the response. I started with the ketone and did a Horner-wadsworth-emmons to prepare this molecule. There is no CH2 separating the olefin and the C≡N. It is just cholesterol=CH-C≡N. Please check your messages.

Thanks.

Nescafe.

[Archer]

So it's this then



So the general literature on this reaction suggests that the product is predominantly Z. I am not familiar with this reaction as to why Z predominates but judging by how far round the 5-membered ring you have to go to assign Z there may be some E present. i will need to look into the reaction in more detail. Regardless, in your hydrogenation both E and Z should react on the same face of the molecule.

The question is, which face would be more hindered to syn attack during hydrogenation by the conformation of the steroid backbone?

Which do you think?

[Nescafe]

So it's this then



So the general literature on this reaction suggests that the product is predominantly Z. I am not familiar with terrhis reaction as to why Z predominates but judging by how far round the 5-membered ring you have to go to assign Z there may be some E present. i will need to look into the reaction in more detail. Regardless, in your hydrogenation both E and Z should react on the same face of the molecule.

The question is, which face would be more hindered to syn attack during hydrogenation by the conformation of the steroid backbone?

Which do you think?

Thanks for the response. The bottom face is less hindered so I was expecting a syn addition from that face. But I see a 50:50 which makes me question the paper since there is no supporting I'm asking to see what others think.

Thanks again
Nescafe.

[Archer]

So do you get no discrimination at all? Is there even a slight bias for one of the diastereoisomers?

[Nescafe]

I see a 60% of what the author's report and 40% of the other isomer. I was wondering if this is unusual since based on that paper it is almost a 100% conversion to one isomer. Might have to contact the authors directly.

[Nescafe]

Reaction wise, I basically dissolved in a 1:1 THF:MeOH mix with 10% by weight Pd/C and bubbled Hydrogen.

[Archer]

This is not as unusual as you might think, particularly with letters rather than full papers. It could be down to the carbon used to support the catalyst.

Just to be crystal clear did you start with the following saturated ketone?



You didn't start by oxidising cholesterol to the ketone.

[Nescafe]

I hear you.

Yup, that is what I started with!

[Archer]

I would write to the corresponding author if your results contrast theirs so much. It might be an honest mistake. It's not like its a paper from the 1940's.

I have helped a number of people who contact me because my methods, one of which was extremely temperamental if water got into it.

Never had someone call twice so I take this as a good sign.