[Alohaey]

Hi all

At first I want to mention that this is an assignment question and I do not expect a full answer, however I'm looking for some starting help to get me going since I'm totally stuck.

We have to design a synthesis of A (see attachment) from B. My first thought was that the oxygen is easier replaced than the two methyl groups in B. Therefore I assume that the two methyl groups in A are the same ones in B. For ring formation the Diels-Alder reaction would be suitable. However if I react it with an alkene I get D which has the two methyl groups on the 3. position and not the 2nd. That where I got stuck. Otherwise I would try to use a Beckmann rearrangement which inserts the nitrogen before the ketone etc.

Any help would be appreciated.

Alohaey

[kryptoniitti]

I worked something that is similar to your problem to get you started. The important part is to get diene from the ab-unsaturated ketone, you can experiment with various substituted dienenes and dienophiles for the later D-A ring formation.

[Alohaey]

Hi kryptoniitti

Thanks alot for your help. That's definitely a big help. Now I just have to think how to deal with that the grignard reagents don't attack the wrong ketone and react with itself.

Thank again
Alohaey

[macman104]

Are you talking about the grignard in the first step?  There should be no chemoselectivity issues.  The grignard won't attack your double bond, and there is only one ketone.

[Alohaey]

I'm talking about if I modify kryptoniitti's displayed mechanism to my reaction since the attachment to the grignard reagent would have a nitrogen and also a double bond (see diagram in first post). However I think I found a solution to the answer by using a stabilised oxophosphonate. The picture I attached is the reaction  pathway I have now submitted. Hopefully there are not too many mistakes in it :-)

Thanks again for your help guys
Alohaey