Synthesis of pyrazinyl compounds from glycerol and 1,2-propanediamine over Cu–TiO2 catalysts supported on γ-Al2O3

Cu–TiO2 catalysts supported on γ-Al2O3 are prepared and used in glycerol cyclization with 1,2-propanediamine to produce pyrazinyl compounds including 6-hydroxymethyl-2-methylpyrazine, 5-hydroxymethyl-2-methylpyrazine, 2,6-dimethylpyrazine and 2,5-dimethylpyrazine in a fixed-bed system. It is found that glycerol cylclization with 1,2-propanediamine gave a high total yield of pyrazinyl compounds (>80%) over Cu–TiO2/γ-Al2O3 catalyst, and cyclization was through the reactions between activated 1,2-propanediamine and the intermediates from glycerol dehydration and oxidation. In addition, the regioselectivity of the pyrazinyl compounds was mainly controlled by the steric hindrance of the substrates during the cyclization process.

Graphical abstractThe Cu–TiO2/Al2O3 can catalyze either dehydrogenation or dehydration of glycerol to yield glyceraldehyde or hydroxylacetone, respectively, both of which subsequently cyclize with activated 1,2-propanediamine to produce the corresponding pyrazinyl compounds.Figure optionsDownload full-size imageDownload as PowerPoint slide