Synthesis of 2,3,4,5-tetrasubstituted pyrroles and 1,4-dihydro-tetraarylpyrazines using acidic alumina as a heterogeneous catalyst

Some new 2,3,4,5-tetrasubstituted pyrroles were synthesized via three-component condensation reaction of benzoin derivatives, 1,3-dicarbonyl compounds, and ammonium acetate using acidic Al2O3 as an efficient and reusable heterogeneous catalyst in refluxing ethanol in high yields. Also, acidic alumina was catalyzed 1,4-dihydro-tetraarylpyrazines by the condensation reaction of benzoins and ammonium acetate in refluxing ethanol in high yields. Alumina showed much the same efficiency when used in consecutive reaction runs.