Hey E 109!
Osmium replied to it a few times.
All the info I have on this is what I've posted here. I've just seen it in two books I've bought to learn general org. chem. They do not deal with special things so this can only be a hint into the right direction.
I don't know at all, if it works. I don't have a lab, sadly. But I know that to replace a secondary halogen you need a good nucleophile. I know NH3 is just a so-so nucleophile. And I know that the most expensive of my books sez K-phtalimide is a very good nucleophile. So all I can do with this info is combinig it and say: "Why not give it a try, the theory looks good". I also still have no library access but I will have in 2 weeks. I hope then I can give/get more refs and such.
Im not very up to date when it comes to Cl/Br/I-Safrole but have a look at this:
Al2O3 with H2O on it's surface + COBr2 -->
Al2O3 with HBr on it's surface + CO2
(also works with SiO2 and PI3/SOCl2)
this Al2O3 with HBr on it's surface reacts with alkenes to the halo-alkane with CH2Cl as solvent in 20min and 99% yield.
Here's the ref: Kropp, P.J., K.A. Daus, M. W. Tubergen, et al., J. Am. Chem. Soc., 1993, 115, 3071. Surface-mediated reactions. 3. Hydrohalogenation of alkenes.
Have fun and please report any dreams you may or may-not have dreamt.
--psyloxy--