[Ranowa]

I've been given the structure for "Compound A"; it's just a cyclononane with a double bond to Oxygen at one of the Carbons, and a Deuterium bonded at an adjacent Carbon in place of an H. I can only use a restricted list of reagents in my retrosynthesis (it breaks down to the reagents for a few simple addition mechanisms, but almost all have D instead of H).

My current idea is to use D2/Pt, one of the possible reagents, and my plan is catalytic reduction. My starting compound would be the cyclononane, no deuterium, with a double bond between the Carbon with the oxygen and an adjacent Carbon. In my head, the catalytic reduction takes place, but because of the double bond to O and the ring structure Deuterium can only attach at one of the Carbons. My main worry is that either catalytic reduction just doesn't work the same with D instead of H, or that the Ds will go after more than the double bonded Cs and will attack both alpha Carbons and I'll end up with one extra Deuterium. Am I thinking on the right track/are my concerns valid?

Edit: Just now realized that my thinking would have five bonds attached to a Carbon in the starting compound. *facepalms self. This was my only idea... can anyone help me get started on the right track?

[Babcock_Hall]

What do you know about ketone chemistry?  With respect to most chemical reactions, deuterium is slower due to the primary kinetic isotope effect, but will otherwise react the same as hydrogen.  Do you have to add only one deuterium at the carbon in question, or is it OK to add two?

[Ranowa]

The final product must equal the cyclononane with the ketone and the single Deuterium. I know next to nothing about Deuterium chemistry, unfortunately; it's only covered on a single page in my entire textbook and we haven't done it in class :/

I've written out a possible hydrobromation, but with BD3 instead of BH3. Of course, this yields an alcohol (does OD still even count as an alcohol?) instead of a ketone, and I'm not sure if my way to convert it works. I've written out this so far:

Deprotonate H2O2 with NaOH. Then add the H-O-O minus product to the cyclononane. Hopefully, it would steal the D off the alcohol and a double bond would form. But I'm entirely unsure if this would actually work or if this is just wishful thinking.

[Babcock_Hall]

Based on your OP, I am not sure whether or not the starting material is chosen for you or not.  In the latter case you would have the freedom to choose any starting material you wished.  Can you clarify that point?

[Ranowa]

I _think_ that the starting material is free for me to choose. All that's provided for me is the final product and then a list of reagents, and of course there's more than one right answer, so I think it's mine to choose.

[Babcock_Hall]

D₂O is a common source of deuterium.  My original thought was to take the ketone and soak in basic D₂O; however, this would deuterate more than once.

[sjb]

What reactions do you have listed? Do you know how to add once alpha to a carbonyl? What is your sm?

[Ranowa]

Sm? Not sure what that is. I also don't know how to add one alpha to a carbonyl- but, my process isn't limited only to what we've done in class. My possible reagents are:

BD3, Hg(OAc)2, NaNH2, NaOH, NaH, H2O2, H2O, NaBD4, H2/Pt, D2/Pt

[sjb]

Apologies, sm == Starting material.

Now you've listed your possible reagents this is starting to get a little clearer. Perhaps consider https://en.wikipedia.org/w/index.php?title=Ketone_halogenation&oldid=614110698 or similar?