Radical reactions are finicky by nature. I know i've seen some NBS brominations that worked in the presence of water, but I can't seem to find them right now.  They were in wierd journals (not ACS or RSC if I remember correctly), but they worked.  I think they were in biphasic DCM/water solution and were heterocycles. 

The lab purifications book has a warning benzoyl peroxide being explosive when dry (as most peroxides and similar reagents are).  It has a few methods of purification (I would avoid using acetone or ether during purification, just for safety). Maybe make a solution in something like DCM and dry with mole seives?

Have you tried AIBN as the catalyst? It's easy to handle in my (very limited) experience, and comes pretty darn pure usually. 

http://pubs.acs.org/doi/abs/10.1021/jo971067g

Check the refs and forward search this on ISI for more info? 

Let me know if that helps,

-Kyle

I'd echo what Kyle said. We've used benzoyl peroxide and AIBN in our NBS brominations, and I've never found any real advantages to the benzoyl peroxide. Recently, we've gone to using thermal activation of AIBN, and using benzene as a solvent. Nice strong bonds that won't get activated, boiling point at a good level for thermolysis of AIBN, easy to remove. Yields are good, but finicky. 

Along those lines, Aldrich has a handy sheet of thermal initiators for radical processes with their rates at various temps in the corresponding solvent:

http://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Aldrich/Gene…

-Kyle

I found the papers I mentioned earlier while looking up brominations to help a student.  Here's two relevant papers, the first being the most applicable to doing radical reactions "on water"... they use mixed water/organic solvents (including benzene as one of the solvents). The second one shows examples of comparing various radical initiators with photolysis, and photolysis works out well in some cases.

Tetrahedron Letters 2002, v43, p1697

Tetrahedron Letters 2006, v47, p1097

I hope this is useful, I know this thread is a little old.

-kyle

Ha!  I think it's funny that Kyle thinks TetLett is some "weird journal".

Ha! I think it's funny that Kyle thinks that this thread (at 3 months) is "old." I bet Nick hasn't even found a student to run the reaction yet :)

Heh, Tettlett is definitely not some wierd journal, i thought the papers I was thinking of were in really esoteric journals for some reason... the sad thing is I think many people in the department are probably unaware that it even exists (silly young grad students).

and also for some reason I thought this thread was older than it is. My grasp of time is clearly getting even more shaky that it was in college and grad school.

In order to not derail the thread.... Nick (if you get a chance to see this), let us know if you figure out something that works for what you are trying to do.

I'll throw another reference out there... you can use H2O2/HBr in water to brominate with high selectivity:

Tetrahedron 2009, v65, p4429

-KyleFinder (its kinda like Scifinder, but you just ask Kyle)*

*my labmate came up with that at group meeting when he was presenting