We have investigated the effects of Li on the structure, surface basicity and catalytic activity of MgO for the synthesis of flavanone. Introduction of low amounts of Li (i.e., <= 0.1 wt.%) was found to promote the rate of the Claisen-Schmidt condensation reaction, which is the first step in this process. However, at Li loadings above 0.1 wt.% a detrimental effect was observed, due to a concomitant decrease in surface area and increase in MgO crystallite size. A strong correlation was observed between surface-normalized basicity and catalytic activity. The increase in activity at higher levels of surface basicity can be attributed to the increased ability of Li-O- pairs to abstract a proton from the 2'-hydroxyacetophenone reactant, thus facilitating the adsorption and subsequent surface reactions of this molecule. (C) 2010 Elsevier B.V. All rights reserved.