New Synthesis Method of 2-Phenylimidazoline

According to the different reaction materials, the synthesis method of 2-phenylimidazoline can be divided into the following three types:

1)Ethylenediamine reacts with phenylacetonitrile

Vogelbacher et al. mixed 10 g of benzonitrile, 6.0 g of ethylenediamine, 0.075 g of sodium sulfide and 0.15 g of concentrated sulfuric acid at 130 to 165 C for 20 h, light yellow needle crystals of 1.5 g, and 2-phenylimidazoline was recrystallized with THF.

2)Ethylenediamine reacts with benzoic acid

3)Ethylenediamine reacts with benzaldehyde

Li Tianyu chose ethylenediamine and benzaldehyde as raw materials to synthesize 2-phenylimidazoline, and catalyzed hydrogen peroxide with phosphorotungstic acid / tetert-butylammonium bromide, the yield of 2-phenylimidazoline can reach 93.7%.

Hong et al reported a method for rapid and mild synthesis of 2-phenylimidazoline: with ethylenediamine and benzaldehyde as the reaction substrate, dichloromethane as the solvent, NBS as the catalyst, sonication 25 min to obtain 2-phenylimidazoline, the yield of 2-phenylimidazoline was 78.1%~99.0%.

Gas-phase dehydrogenation of 2-phenylimidazoline

The catalysts used for gas phase dehydrogenation of 2-phenylimidazoline are: ZnO, Zn-Al2O3, NiO, SiO2 and silicate. Gas phase catalytic dehydrogenation requires the reaction temperature, the activity of the catalyst and the conditions of the reaction equipment, and it is difficult to be applied in industrial production.

Liquid-phase dehydrogenation of 2-phenylimidazoline

The reaction conditions of liquid phase dehydrogenation are relatively mild and are of certain industrial research value. The commonly used liquid-phase dehydrogenation catalysts are as follows:

(1)Ni-Al catalyst: The catalytic system is widely used in the industrial production of 2-alkylimidazole compounds, but it is generally effective for the synthetic production of 2-arylimidazole compounds.

(2)MnO2 Catalyst: MnO2 is a green imidazoline dehydrogenation agent, which can effectively improve the selectivity of the reaction, but the reaction requires at least 24 h to obtain satisfactory yield.

(3)BaMnO4 Catalyst: Hughey prepared fresh BaMnO4 for oxidation and synthesis of imidazole, and the catalyst still needs more than 22 h to achieve a relatively satisfactory yield.

(4)Loaded KMnO4 catalyst: Mohammadpoor-Baltork et al. prepared KMnO4 / SiO 2 loaded catalyst for the dehydrogenation of 2-phenylimidazoline. The yield of 2.5 h at room temperature can be as high as 79.9%, but the strong oxidant of potassium permanganate will cause some harm to the environment.

(5)Other new catalysts: Hadi Kargar reported a catalyst —— multiwalled carbon nanotube that can be used to catalyze the oxidation of 2-substituted imidazoline to 2-substituted imidazole. This method used water and methonitrile as the solvent, the reaction was 96%; Aiki, et al, prepared a new cyclic metallized Ru (III) complex with 2-phenylpyridine, and proved the improvement of the electron supply capacity of cyclic metallized ligand, improved the catalytic activity of Ru complex for oxidation dehydrogenation of 2-phenylimidazoline, and enabled the catalytic dehydrogenation of 2-phenylimidazoline in air at room temperature.

Alkylation method

Qi Gang et al. used imidazole and iodine benzene as raw materials to select nanoparticles in the dimethylformamide (DMF) solvent.

Ni and cuprous iodide (CuI) were used as catalysts for 2-phenylimidazole synthesis.

Other methods

methodThe 2-PZ yield /%
The α -aminoacetal method 35
Claisen Rearrangement reactionNo reports
The Retro-Diels-Alder method54
Tetrazole photosensitive synthesisVery low (as a byproduct)
other methods

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