[Rutherford]

I need help with solving the attached scheme. I know that Br₂ with CH₃COOH are used for alpha carbonyl substitution, but what for is used Br₂ with CH₃OH?

[discodermolide]

How about it forms a bromomethyl ketone, which is treated with a base and diethylmalonate, which after hydrolysis and acidification decarboxylates to give the product?

[Rutherford]

Okay, it's alpha carbonyl substitution again. Why are two isomeric products obtained (N and O)?

[discodermolide]

Presumably you get substitution at both of the methyl groups? Or di-substitution of one methyl group?

[Rutherford]

Is this the final product?

[discodermolide]

Could very well be correct!
As well as the mono-substituted product.

[Rutherford]

The problem is about cyclobutane compounds so all clues lead to this. I posted merely a part of the whole synthesis, so if I get stuck with the other parts I will feel free to post. Thanks very much disco.

[Rutherford]

Here is another scheme. The final product is the same compound A. What are OsO₄ and NaIO₄ used for?

[discodermolide]

Osmium tetroxide is used to produce diols from olefins. Usually it is used catalytic ally. The sodium periodate oxidizes it back to the tetroxide.
This is done because osmium tetroxide is very toxic and expensive, it is quite a volatile compound so this method reduces the quantities used.

[Rutherford]

Compound A is the same compound A in the previous scheme (I attached the compound image few posts before-the cyclobutane). It is not a diol, so maybe the periodate oxidized the diol to compound A, and as M is an olefin it should be methyl-cyclobutane, but how could it be obtained from compound L?

[Dan]

It is not a diol, so maybe the periodate oxidized the diol to compound A,

Yes, as well as acting as the stoichiometric oxidant in the osmium-catalysed dihydroxylation, periodate will oxidatively cleave the diol (periodate cleavage).

and as M is an olefin it should be methyl-cyclobutane, but how could it be obtained from compound L?

I am confused by this. methylcyclobutane is not an alkene....

Assuming that your structure for A is correct (which I think it is), I would guess that M is:




Also, from the first part, I think N might just be HBr.

[Rutherford]

I thought first time that N is HBr too, but N and O are isomers.

"I am confused by this. methylcyclobutane is not an alkene...."
I don't know what I was thinking about. Thanks for the correction.

Now, M is the compound you attached. Is K then 2-propen-1-ol?

[Dan]

Now, M is the compound you attached. Is K then 2-propen-1-ol?

Can you explain how you came to that conclusion?

[Pranav]

How about it forms a bromomethyl ketone, which is treated with a base and diethylmalonate, which after hydrolysis and acidification decarboxylates to give the product?

Could you please explain why alpha substitution takes place?

[Rutherford]

Now, M is the compound you attached. Is K then 2-propen-1-ol?

Can you explain how you came to that conclusion?

If M is the compound you draw, I thought that the KOH was used for elimination (dehydration, one -OH and -H left the molecule) and the H₃O⁺ was used for transforming -CN to -COOH, then L is the attached compound. As L is made from cyano-ethene and K (addition of alkenes, one to another), K should be 2-propen-1-ol. Did I went wrong somewhere?