Selective synthesis of 3-methyl-2-cyclopentenone via intramolecular aldol condensation of 2,5-hexanedione with γ-Al2O3/AlOOH nanocomposite catalyst

Selective intramolecular aldol condensation of 2,5-hexanedione (HD), which is producible from 5-hydroxymethyl-2-furaldehyde (HMF) via hydrogenolysis and successive hydrolysis, towards 3-methyl-2-cyclopentenone (MCP) is examined with various solid acid catalysts. It is found out that the simple aluminum oxides such as gamma-Al2O3 and AIOOH gave an attractive performance for the MCP generation from HD with high selectivity (> 71%). After the hydrothermal treatment for 6 h on gamma-Al2O3 to modify its acidity, it is found that as-prepared gamma-Al2O3/AlOOH nanocomposite exhibits the yield of 77.2% with the highest selectivity of 85.9% for MCP.