Diels-Alder and Synthesis Problem: Confused about how to add carbon chain and double bonded oxygen

[![Synthesis Problem](https://i.stack.imgur.com/XpiUb.png)](https://i.stack.imgur.com/XpiUb.png)


I am working on this synthesis problem. My first step was converting the dienophile given into a diene via E2 elimination. From the product given, I concluded that the dienophile will carry the double bonded oxygen. I think I understand how to draw the Diels Alder reaction.
However, I am stuck on how to generate the carbon chain from the two wedges.
I appreciate any help or hints.




*Conceptually*, you may think about the right hand hemisphere of the target molecule as derived from butane-1,4-diol:


[![enter image description here](https://i.stack.imgur.com/GhXSV.png)](https://i.stack.imgur.com/GhXSV.png)


You would use its bis-enolate as substrate for a Diels-Alder reaction with a (*Z*)-configurated dienophile. This aims to install R' and R'' on the same side of the cyclohexene built (*cis* relationship). There would be multiple functional group interconversions (FGI); reduction of the double bond in the cyclohexene, cleavage of the ether groups, oxidation of the then revealed 1,4-diol into a 1,4-dione (without tapping into an analogue of the redox couple of hydroquinone / benzoquinone).


The diene exhibits a pattern of six carbon atoms between the two carbonyl-C, thus *on paper* one way to disconnect this one were an ozonolyis (reductive workup):


[![enter image description here](https://i.stack.imgur.com/waaH5.png)](https://i.stack.imgur.com/waaH5.png)


A bibliographic search should query for examples where the triple substituted diene reacts faster than the double substituted. One plausible access to the diene (to perform the ozonolysis) could be the Birch reduction of toluene.


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