Using Tandem Mass Spectrometry to Predict Chemical Transformations of 2-Pyrimidinyloxy-N-Arylbenzyl Amine Derivatives in Solution

Tandem mass spectrometry is used to predict the chemical transformations of 2-pyrimidinyloxy-N-arylbenzyl amine derivatives. Compound 1, N-2-2-4,6- dimethoxypyrimidin-2-yloxy benzylamino phenyl benzamide was selected as a model to present our idea. The CID reactions of protonated 1 include an intramolecular SN2 reaction and a cyclodehydration reaction. Under in-source CID conditions, deprotonated 1 undergoes a Smiles rearrangement reaction and then dissociates to the ion at m/z 349. Theoretical computations were invoked to shed light on the reaction mechanisms of 1 by the semiempirical PM3 method. These studies of gas-phase reactions show the reactivity of some potential reaction centers in this molecule, which inspired us to explore the solution phase analogous reactions of 1. Further experiments show that 1 has two analogous reactions in acidic solution: the acid-catalyzed cyclodehydration reaction and the acid-catalyzed Smiles rearrangement reaction. Moreover, 1 undergoes the base-catalyzed Smiles rearrangement under basic conditions. The present study demonstrates that mass spectrometry can play an important role in predicting the chemical solution phase transformations of 2-pyrimidinyloxy-N-arylbenzyl amine derivatives.