Herein, we describe a practical approach for direct vinylogous aldol condensation of Biginelli product for carbon–carbon double bond formation at methyl group of 6-methyl dihydropirimidinone by using hydrated ferric chloride. With aromatic aldehydes, the method yields stereoselectively trans products. The olefination reaction is applicable with aldehyde without chelating (with Fe III) functional group. DHPMs with carboxylate ester and arylidene at C-6 methyl are not known. The method opens up a new avenue for the synthesis of a wide variety of DHPMs. The olefin products were subjected to dihydroxylation reaction.
