[darkdevil]

Hi all, Here is the problem:

I am doing an N-alkylation of a secondary amine with triphenylmethylbromide. When I monitored the progress by TLC. I observed many different spots (around 6 major spots, some minor spots are hard to observe).(which I expected only 2 spots should be observed, "MONO" and "BIS" N-alkylation since there are 2 identical secondary amine on the molecule )

I wonder if the other spots on the TLC are due to triphenylmethyl cation rearrangement? Like the image below:



Should I expect the tertiary triphenylmethyl cation to rearrange itself to a less stable secondary cation?
I carried out the reaction at room condition, and I am trying to do it again later at lower temp. and one at a higher reflux temp.

[discodermolide]

Do you not mean triphenylmethylbromide, Tritylbromide?
I don't see where the phosphorus comes into it.

[darkdevil]

oh yess im sorry.
it should be triphenylmethylbromide

[discodermolide]

The trityl group is quite acid labile so it may be coming off on the TLC plate. I would use neutral alumina plates, or try adding a little triethylamine to the TLC solvent, I mean a little. This should stop it coming off on the plate.