[Chaste]

Hi all, from the above picture, I want to find out how to convert the grignard reagent, with its C=C becoming a CHO.

and can d3-SnBu3 be a d3 synthon reagent as well?

[Doc Oc]

I'm a bit confused, are you trying to convert the aldehyde on the left into the alkene on the right?  FYI, you will not be able to carry a Grignard through multiple synthetic steps, so you will need to make that last.  Same goes for the stannane, although they are more stable.

[Chaste]

I'm a bit confused, are you trying to convert the aldehyde on the left into the alkene on the right?  FYI, you will not be able to carry a Grignard through multiple synthetic steps, so you will need to make that last.  Same goes for the stannane, although they are more stable.

hi, my question is how to convert the grignard on the right to the ketone on the left.

[jake.n]

So you want to describe a way to add the aldehyde group as a grignard, then recover the aldehyde?

For the one of the left, acetals are used to protect ketones and aldehydes and you should be able to find several easy routes back to the carbonyl.
For the alkene, you should be able to find an appropriate oxidation from your sophomore O-chem book.

[Chaste]

I can use ozone with triphenylphosphine to get the aldehyde from alkene right? That's what I wanted to ask

[Doc Oc]

Yes, ozonolysis will convert that alkene to the aldehyde.  But triphenylphosphine isn't used in that reaction, I think you're confusing Wittig conditions.  Again, the Grignard will not survive that step, I'm not sure if that's what the minus symbol is supposed to be on the aldehyde (d3).

[Chaste]

hmmm isn't triphenylphosphine a quenching reagent for ozonolysis?

so, what you mean is grignard won't survive ozonolysis reaction?

[discodermolide]

hmmm isn't triphenylphosphine a quenching reagent for ozonolysis?

so, what you mean is grignard won't survive ozonolysis reaction?

You obviously should read up about Grignard reagents and their properties, they do not survive much at all, as for ozone!!!!!!!!!!!!!!!

[jake.n]

I think you are correct in that you are identifying a reagent that is used in synthesis that can be used later to deliver the aldehyde.  Of course the Grignard will not survive the ozonolysis, but by the time you uncover the aldehyde, the grignard will have already been used as a nucleophile.

http://en.wikipedia.org/wiki/Synthon

In the example here, the cyanide is used as an acid synthon.  It is first used as a nucleophile, then hydrolized to give the acid at the end of the synthesis.

Similarly, your grignard reagent would be first reacted with an electrophile.  Then you would perform ozonolysis later to "uncover" your aldehyde.

[Chaste]

Yea, grignard reaction first then the aldehyde.

[Doc Oc]

hmmm isn't triphenylphosphine a quenching reagent for ozonolysis?

Not as far as I know, typical reagents are Zn/H₂O or Me₂S

[orgopete]

I am going to try to read between the lines here. The poster is in a mix and match class in which strategy is more important than mechanism. Hence, it appears as though reagents are thrown together without thinking of how they react. I also argue that could be construed from the original question.

Triphenylphosphine can be used to reduce ozonides. It probably isn't the most popular reagent as it leaves triphenylphosphine oxide to be separated, but nothing wrong with it being the reductant. Same mechanism as dimethylsulfide.

[Doc Oc]

I am going to try to read between the lines here. The poster is in a mix and match class in which strategy is more important than mechanism. Hence, it appears as though reagents are thrown together without thinking of how they react. I also argue that could be construed from the original question.

I understood that just fine, I just don't think it should be an excuse to show questionable chemistry.

[jake.n]

I don't understand what is questionable about it.  Grignard addition followed by ozonolysis is a perfectly acceptable way to add the desired aldehyde to a product.  The grignard cannot react with the aldehyde if you wait to uncover it until after adding the grignard.  The point is to find an indirect way to add the group.

[Doc Oc]

The Grignard doesn't add to anything, the net change is 0 if you look at the d3 synthon, it's become a carbon with a - charge on it.

Looking back, I may have misinterpreted what orgopete was saying.  Pete, if you're suggesting that part of the importance is picking out the correct strategy (ie; what we're talking about with the Grignard needing to react first) then I agree.  However, if you're suggesting it doesn't matter because the class is focused on single reaction transformations and all the poster needs to focus on is coverting the alkene to the aldehyde then I don't agree at all.