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[choupi]

In attempting to solve this synthesis problem.
http://i.imgur.com/TjMTB.png

Could the following work ?

cis-1,3-butadiene + ethene giving cyclohexene

followed by Br2, hv and then a BBB to give elimination and a diene to react with an doubly CN substituted ethene ?

[discodermolide]

What are you going to do with the exo isomers?

[LennoxTutoring]

Use of but-2-enedinitrile will result in endo stereoselectivity due to secondary orbital overlap.

the Diels-Alder Reaction, Part I
http://lennoxtutoring.com/2011/11/23/the-diels-alder-reaction-part-one/

My concern is your use of a Lindlar catalyst. What does hydrogenation with a Lindlar catalyst do to alkynes? What does it do to alkenes?

If you're careful, you can reduce the alkene with 5% Pd/C under hydrogenation conditions. This is more active than a Lindlar catalyst. You can also do the reduction with diimide, which will be specific for the electron rich alkene.

Electron rich things usually reduce before electron poor things in hydrogenation reactions.

[discodermolide]

Lindlar's catalyst is excellent for the reduction of alkynes to cis olefins without over reduction. In all the times I have done it  I never observed over reduction. On the other hand using Pd/C 5% is very difficult to stop and in my experience you always get over reduction to the alkane.