A 1,3,5-trimethyl-2,4,6-tris(3,5-dialkyl-4-hydroxybenzyl)benzene is prepared in high yield by reacting a 2,6-dialkyl-4-methoxymethylphenol with mesitylene in a hydrocarbon solvent and in the presence of at least about 10 mol %, based on the amount of mesitylene, of a hydrocarbon-soluble acid (e.g., an alkylbenzenesulfonic acid having 12-18 carbons in the alkyl group, a carboxylic acid, or a dialkylsulfosuccinate) as a catalyst or co-catalyst while distilling methanol by-product out of the reaction mixture as it is formed. The process may be conducted so as to provide a substantially pure product or a product, such as 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, having fairly high purity (e.g., about 98-98%) and a melting point much lower than would be expected of a product having such high purity.
