Mass spectrometric studies of the gas phase retro-Michael type fragmentation reactions of 2-hydroxybenzyl-N-pyrimidinylamine derivatives.
The gas-phase fragmentation reactions of 2-hydroxybenzyl-N-pyrimidinylamine derivatives (Compounds 1 to 6), the O-N-type acid-catalyzed Smiles rearrangement products of 2-pyrimidinyloxy-N-arylbenzylamine derivatives, have been examined via positive ion matrix-assisted laser desorption/ionization (MALDI) infrared multiphoton dissociation (IRMPD) mass spectrometry in FT-ICR MS and via negative ion electrospray ionization (ESI) in-source collision-induced dissociation (CID) mass spectrometry, respectively. The major fragmentation pathway of protonated 1 to 6 gives the F ions under IRMPD; theoretical results show that the retro-Michael reaction channel is more favorable in both thermodynamics and kinetics. This explanation is supported by H/D exchange experiments and the MS/MS experiment of acetylated 1. Deprotonated 1 to 6 give rise to the solitary E ions (aromatic nitrogen anions) in the negative ion in-source CID; theoretical calculations show that a retro-Michael mechanism is more reasonable than a gas-phase intramolecular nucleophilic displacement (SN2) mechanism to explain this reaction process.
Wang
Hao-Yang
HY
Shanghai Mass Spectrometry Center, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 200032, Shanghai, China.
Zhang
Xiang
X
Shanghai Mass Spectrometry Center, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 200032, Shanghai, China.
Guo
Yin-Long
YL
Shanghai Mass Spectrometry Center, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 200032, Shanghai, China. ylguo@mail.sioc.ac.cn.
Lu
Long
L
Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai, People's Republic of China.
D000588:Amines / Q000737:chemistry*; D003198:Computer Simulation; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D011743:Pyrimidines / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*
D000588:Amines; D011743:Pyrimidines