Phosphorus mediated imidazolinium to oxazolium ring rearrangement.

An unexpected rearrangement occurred when an imidazolinium based OCO pincer-type ligand (1) reacted with PCl3 producing a chlorophosphine with a pendant oxazolium "arm" (3). The mechanism of this rearrangement was studied both experimentally and by density functional theory (DFT) computations. The deprotonation of 3 led to further unexpected results.