[lfga94]

Hello everybody!

I'm working on the N-arylation of theophylline, a methylxanthine. I'm using theophylline and 2-chloropyridine as substrate, K₃PO₄ as the base, CuI as catalyst and TMEDA as the co-ligand (to stabilize the copper). The solvent is DMF and I'm working with inert atmosphere. After the reaction, a solid remains in the bottom; it seems orange but when I filter and wash it, it turns gray. I was wondering if anybody have an idea of what it could be. It isn't the product of interest, I obtain it from the extraction of the solution.

[pgk]

Either you have formed an insoluble copper(I)-theophylline complex that changes color after washing, by clustering molecules of the washing solvent (water?); or you have formed an Ullmann dimerization product (CuI/TMEDA in hot DMF) that changes color, under neutral conditions. But you can verify it by taking a 1H-NMR spectrum.