[Walker]

it s simple homework  a bicycle sinthesis (not really sure on the english spelling)
found the required reactives for the correspondong diels alder reaction.

but one of the components is a ciclopentadiene and its need to be made from scratch (no stoichometry required)

it all done in the paper efficiency is irrelevant.

So i go CaC2 +H2O = etyne C---C (triple bond)

join carbon chains with organometalic reactions.

them im stuck with 1-3 pentadiene and It doesnt look like any amount of heat or radiation will make it a cycle.

what should I do? Im taking the wrong approach? or is there a way to make it by some weird diels alder or the like (butadiene+???)

[kiwi]

do you want cyclopentadiene, or a substituted form? you can make unsubstituted cyclopentadiene by cracking dicyclopentadiene in a retro-Diels-Alder reaction.
Substituted cyclopentadienes are a little harder, but there are a few ways depending on what level you're at. Simple approaches (on paper!) include grignard addition to cyclopentenone then elimination; more complex approaches might rely on a catalytic cyclisation of alkenyl-allenes with a something like gold(I)phosphine complexes.

[Walker]

thanks for the input can you elaborate on the cyclization of alkenyl alkenes
since I forgot to mention every organic compound to be used must be synthetised from inorganic reactions.

electrocyclic through conjugated alkenes is the base knowledge i have.