[poorGRADstudent]

Hi Everyone,

I have a quick question regarding one of my reactions. I recently performed a stille reaction and it worked great. The only issue was that it seemed almost like some of the Pd cat. was traveling through the silica. Very strange I know. Most of my compound came off of the column fine except for the last few fractions I collected, which was this thick brown liquid. Also, when I was running the column instead of an even band traveling down the column it was more of a line streaking down. On TLC there was no streaking. Any ideas what this brown stuff is co-eluting with my compound? Thanks for the help in advance!!

Few side notes:
-Reaction was done with Pd(PPh3)4, in dioxane under Ar
-Workup was aq. KF and EtOAc
-All solvent was removed and residue was loaded on silica before the column
-Solvent system was 4:1 Hex/EtOAc

[TheUnassuming]

Tetrabutyltin complexes everything and makes them streak and elute in very undesirable ways.  Triphenylphosphine can also make purification a pain.  For my compounds I've usually needed to run multiple columns to get spectroscopically pure product.

[poorGRADstudent]

Tetrabutyltin complexes everything and makes them streak and elute in very undesirable ways.  Triphenylphosphine can also make purification a pain.  For my compounds I've usually needed to run multiple columns to get spectroscopically pure product.

Fortunately, the fractions I collected were pure (by NMR) and equated to approx. 60% yield, which is fine with me. Honestly, I would be fine never doing another stille coupling again.

[clarkstill]

A colleague found this method to be very helpful, although his problem was removal of Bu3SnI, not the palladium catalyst.

http://pubs.rsc.org/en/Content/ArticleLanding/2010/CC/c0cc01328e#!divAbstract

[discodermolide]

A tip from an old friend was to partition between acetonitrile/hexane to remove tin residues.