[shiu1]

how can u make 5-methylcyclopenta-1,3-diene starting with cyclopentane? please help. thanks!

[Jorriss]

Have you had any luck?

If you're starting from a hydrocarbon, that generally means radical mechanism. Did you think anything similar?



And, the way I would do this, would probably involve an electrophilic aromatic substitution - somewhere down the line.

[orgopete]

I too would start with a radical bromination. I would then do something like elim-brom-elim-brom-coupling. I am intrigued how an electrophilic substitution can be part of the route though.

[Jorriss]

I too would start with a radical bromination. I would then do something like elim-brom-elim-brom-coupling. I am intrigued how an electrophilic substitution can be part of the route though.

I haven't taken organic so don't kill me if I'm wrong , but here's what I was thinking.

Start with a radical bromination to cyclopentadiene. Add a strong base like LDA to get cyclopentadienide. Electrophilic aromatic additions apply to that compound too, correct?

[orgopete]

@Jorriss, okay. I just thought I was missing something.

[Agathiyar]

Cyclopentadiene as such not stable enough at room temperature, exists as dimer, crack them into monomer, mild base can give anion (aromatic), perform nucleophilic substitution (controlled) with methyl halide.

[uvcyclotron]

Please read the forum rules regarding topic titles..

I too would start with a radical bromination. I would then do something like elim-brom-elim-brom-coupling.

yup, i was thinking along the same lines..a radical bromination, followed by alcoholic KOH elimination, then allylic bromination by using NBS, repeat the elimination, you will get cyclopentadiene.
Use a base like MeNH₂/NH₃, for acid-base type interaction,which is followed by Me⁺ attack on the electron-rich site..