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I think that it is a Diels Alder reaction, but I don't recognize the start materials! First I make the tertiary alcohol from carboxylic acid with organo-lithium reagent; after I try to make a Diels Alder reaction, but I don't find the right conjugated diene and dienophile.

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Supposed that the synthesis does involve a Diels-Alder reaction, it is nowhere written that it is the last step in the sequence.

Take another look at your product and imagine a $\ce{C=C}$ double bond somewhere. Does it now look more like a Diels-Alder product? The $\ce{C=C}$ can be turned to $\ce{C-C}$ using... (You figure that out).

Work your path back from here and try to identify diene and dienophile.


Don't look until you've figured out the diene ;)

Convert acid to ester, 2 x $\ce{MeMgBr}$, Diels-Alder reaction with vinylmethyl ether, hydrogenate double bond. You didn't cheat, did you? ;)

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    $\begingroup$ The vinyl ether reacts with the aromatic alcohol by way of a stereospecific Diels-Alder? Isn't a Birch reduction and subsequent isomerization required? $\endgroup$ – ron Mar 9 '15 at 14:04
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    $\begingroup$ Also, it's probably better to keep the ester intact for an inverse electron demand Diels-Alder with vinyl methyl ether. $\endgroup$ – jerepierre Mar 9 '15 at 14:54
  • $\begingroup$ @ron Sssssssh, there wouldn't be a diene otherwise ;) But this wasn't your or my homework assignment. $\endgroup$ – Klaus-Dieter Warzecha Mar 9 '15 at 16:26
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    $\begingroup$ @KlausWarzecha thank you so much for the clue! I swear that I don't look your complete answer. I think that my dienophile is the aromatic ring, so first I reduct it with Birch reduction. But which is my diene? $\endgroup$ – Paola Stornello Mar 9 '15 at 20:23

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