[Calicum]

C5H8

I was thinking of using Simmons-Smith Reaction on a alkene, but I'm sure anything else I try after will break the ring. Any advice? 

[discodermolide]

This can be done and the ring will survive. Cyclopropanes are even found in nature!
Although in your drawing the C=C is still present.

[Calicum]

Sorry if I wasn't clear in my original post, but I ment if it was possible to add a double bond to a cyclopropane without breaking the ring.

[discodermolide]

Here is a reference where such a molecule is used as a starting material
A diastereoselective Cu-catalyzed addition of diorganozinc reagents to readily available cyclopropene derivatives is directed by ester and oxazolidinone functions with excellent facial selectivity. The resulting cyclopropylzinc reagents can be captured via stereospecific reactions with electrophiles.
V. Tarwade, X. Liu, N. Yan, J. M. Fox, J. Am. Chem. Soc., 2009, 131, 5382-5383.

Note the readily available here.

See also http://www.organic-chemistry.org/synthesis/C1C/cyclic/alkenes/cyclopropenes.shtm

[Calicum]

Thank you, one last thing:



Would using NaF would turn the Si(Me)3 back into a -OH?

[discodermolide]

No, as far as I am aware NaF will desilylate to put a proton there. If it works at all.

[Calicum]

Woops I messed up, I was so used to using that as a protecting group that my brain automatically added the -OH, but if I try to desilylate it won't work? or will destroy the ring?

[discodermolide]

I think the ring will survive depending upon the conditions. Best thing is to do a literature search.

[AWK]

http://hos.ufl.edu/kleeweb/classpapers/substitutedcyclopropenes.pdf