Electron ionization mass spectrometry of curcumin analogues: an olefin metathesis reaction in the fragmentation of radical cations
摘要:
The natural compound curcumin, used in cosmetics, traditional medicines and as a spice in food, is known as a multi-factorial anti-inflammatory agent. To study the anti-inflammatory activity of curcumin derivatives, 24 analogues were synthesized and their structures were confirmed by H-1 MMR and electron ionization (EI) mass spectrometry. Most signals in the EI mass spectra can be attributed to commonly known fragmentations, but the formation of ring-substituted 1,2-diphenylethene (stilbene)-type radical cations, observed in the spectra of all compounds investigated and resulting in the base peak for some compounds, requires a peculiar rearrangement. Metastable ion spectra and C-13 labelling studies show that the stilbene-type ions are formed directly from the molecular ions and contain the two original aryl groups and the 1 and 7 carbon atoms of the olefinic system. It is proposed that the formation of stilbene-type ions results from an intramolecular olefin metathesis reaction; this suggestion is supported by semi-empirical (MNDO/PM3) calculations. (C) 1998 John Wiley & Sons, Ltd.
α-Arylation of β-diketones has been carried out over CuO/aluminosilicate catalyst under ligand-free condition. The reaction conditions were optimized with different solvents, bases, catalyst amounts, and temperatures using acetylacetone and 4-bromobenzaldehyde as a model system. The scope of the catalytic system was extended to include various substituted aryl halides. 27 examples were successfully
Copper(II) and 1,1′-Trimethylene-2,2′-biimidazole-promoted Arylation of Acetylacetone with Aryl Iodides
作者:Jianli Liu、Runsheng Zeng、Chunmei Zhou、Jianping Zou
DOI:10.1002/cjoc.201190083
日期:2011.2
A new and efficient way was developed to carry out the reaction of acetylacetone with aryliodides under the assistance of Cu(II) and 1,1′‐trimethylene‐2,2′‐biimidazole at 100°C. 3‐Aryl‐2,4‐pentanediones were obtained in excellent yields.
A metal-free regioselective oxidative annulation reaction of readily available 2,4-pentanediones with primary amines has been described. This protocol provides a divergent strategy for the incorporation of various radical donors into 5-alkylidene 3-pyrrolin-2-one skeletons, producing a variety of thiionized-, selenolized-, and alkylated 5-alkylidene 3-pyrrolin-2-one derivatives. Moreover, the diverse