Alumina supported Mo catalysts with varying metal:loading (2-12 wt%) were tested in the Biginelli reaction under solvent free conditions for synthesis of 3,4-dihydropyrimidin-2-(1H)-one (DHPM). The DHPM yield increased with Mo loading, going through a maximum for 7 wt% Mo. Alumina supported Mo catalysts appeared to be highly stable and reusable materials for this reaction. A suite of characterization techniques that included X-ray diffraction, Fast Fourier Transform analysis and FTIR of adsorbed pyridine revealed that the DHPM formation is related to the existence of Bronsted acid sites that would be linked to the presence of Al-2(MoO4)(3) phase. (C) 2014 Elsevier B.V. All rights reserved.