[Spiryt]

Hi... I've got a problem:
I have to substitute iodine in compound (1) by bromine, fluorine or (best way) chlorine like in compound (2)... and my question: Is there any straight/direct way to make this reaction?
Thanks & greets

[english]

Elimination reaction to remove I^-.  The alkene can then be treated with HCl or HBr.

I don't know how that ether or HO would affect things.  Doesn't look very good for stabilizing the carbocation intermediate.

[kiwi]

elimination is no good, elimination would give the enol, which would give the aldehyde. are you sure you have the compound as drawn? alpha-chloroethers are very reactive in substitutions, alpha-iodoethers i can only assume are even more reactive. isolation of such a species might be difficult.
Substitution with chloride won't be easy, it is much easier to do the reverse Cl->I substitution. But you might be able to get a F in that position by reaction with excess CsF, the strong C-F bond dragging the equilibrium toward product. If you're lucky.

[english]

elimination is no good, elimination would give the enol, which would give the aldehyde.

Yeah sorry.  Didn't pay any attention to that. 

[Spiryt]

In Vogel i have found somethink like this:
n-hexyl bromide + KF --ethylene glycol---> n-hexyl fluoride + KBr . so maybe it will work when I make my reaction with KBr, KCl or KF (ethylene glycol as a inorganic resolvent)?

[HP]

Fluorination agents which yould work are AgF2 and CoF3 for direct replacement of iodine. I am not sure if AgF would work too but this salt is soluble in water and acetonitrile while the othe Ag-halogenides are not so...As Br2 and Cl2 are more active than iodine may be direct substitution of the iodine is possible. May be solution of Br2 in acetic acid and Ag-acetate as catalys will work for your compounds.

[Spiryt]

Maybe CsCl could work for direct reaction too? And other cesium halogen?

[kiwi]

i would imagine only F or Cl substitution would work well, since you're exploiting:

C-I + MX -> C-X + MI (relatively fast)
C-X + MI -> C-I + MX (relatively slow)

this difference in rates is biggest F>>Cl>>Br> I. From memory, there is ~50-fold difference in reactivity between Cl and Br, but only ~5-fold between Br and I. One side reaction i would worry about with F is that it is very basic, so ring closure to the epoxide will be an issue. I imagine you could use KF at a pinch, but CsX are much more reactive generally due to beeter solvation of the salt in solvents like DMF

[Spiryt]

Hmmm.... and what about the CuCl ? It if soluble in water ... but CuI isn't.... maybe this would work ?
Maybe mercury salts?