[azmanam]

I had a need to lithiate an oxazoline-protected benzoic acid derivative in a directed ortho-lithiation.  I added s-butyllithium to my compound in ether at 0 ^oC.  The solution immediately turned brown.  The lithiation was to stir at 0 ^oC for 4 hours.  I had a seminar to go to, and when I came back, the ice had melted. 

The solution was now green.  So I cooled it back down to zero... and it turned brown again.

A while later, it had started to warm again... And it was green again.  Cooled it back to zero, and it went back to brown.

I thought that was very interesting.  Anyone care to speculate what might be happening?  Different lithium aggregates at different temperatures?