[camptzak]

Can someone explain the second step to me? It seems as though the bond between the hydrogen and the double bonded carbon is acting as a nucelophile, but I know that cannot be correct.

[discodermolide]

Hydrolysis of the lactone with formation of the carbonyl and elimination of the ethoxy group to give the methyl ketone product.

[camptzak]

Hydrolysis of the lactone with formation of the carbonyl and elimination of the ethoxy group to give the methyl ketone product.

after the lactone hydolysis, how does the ethyl vinyl ether attach to the carbonyl group as pictured?

[discodermolide]

Like this?

{MOD Edit: attach converted file)

[camptzak]

actually I was wondering about the addition of ethyl vinyl ether. Its the second arrow in the scheme and the ethyl vinyl ether is in blue.

[TwistedConf]

It seems as though the bond between the hydrogen and the double bonded carbon is acting as a nucelophile, but I know that cannot be correct.

You're actually on the right track.  Your scheme for that step is written a little confusing.  What happens when you react t-butyllithium with the vinyl ether?

[camptzak]

It seems as though the bond between the hydrogen and the double bonded carbon is acting as a nucelophile, but I know that cannot be correct.

You're actually on the right track.  Your scheme for that step is written a little confusing.  What happens when you react t-butyllithium with the vinyl ether?

I would expect it to attack the double bond, like an anionic polymerization initiator, but it seems kind of bulky for that, and I am pretty sure vinyl ethers can not be polymerized anionically.

also, it seems as though i you gave it enough time you would form ethylene and vinyl lithium oxide. but this doesn't make sense here.

I was taught that vinyl hydrogens are not acidic at all, but based on this reaction and the strength of the base it seems like that might be happening. I feel strange saying this though.

[orgopete]

Surely they must have a pKa. If you make an acetylene from a vinyl halide, the proton is removed by base. (This reaction can make you think about that elimination.) Also remember that an acetylenic hydrogen is more acidic still. So, if you mix a very strong base with a very weak acid, what could happen? This scheme would have been better if it more clearly indicated this reaction was carried out first and the product of it added to the imide.

[camptzak]

Surely they must have a pKa. If you make an acetylene from a vinyl halide, the proton is removed by base. (This reaction can make you think about that elimination.) Also remember that an acetylenic hydrogen is more acidic still. So, if you mix a very strong base with a very weak acid, what could happen? This scheme would have been better if it more clearly indicated this reaction was carried out first and the product of it added to the imide.

well based on your hints, I would say that the ethyl vinyl ether undergoes and elimination reaction releasing ethoxide, and then the terminal proton is removed creating an acetlyide. the acetlylide attacks the amide releasing the protected amine and creating a ketone directly connected to a triple bond. The ethoxide that was eliminated is reprotonated at the addition of water and reacts with the triple bond to reform the vinyl ether.

am I close?

[orgopete]

Did you know that a proton can be removed from bromobenzene to form an unstable intermediate anion? Although this will undergo an elimination, a similar reaction with anisole will not. The proton removed from ethyl vinyl ether forms the anion that can form the next intermediate directly.

[camptzak]

Did you know that a proton can be removed from bromobenzene to form an unstable intermediate anion? Although this will undergo an elimination, a similar reaction with anisole will not. The proton removed from ethyl vinyl ether forms the anion that can form the next intermediate directly.

I did not know that, thank you very much