Reinvestigation of synthesis of halo-substituted 3-phenyl-1-(2-pyridyl)-2-propen-1-ones (azachalcones). A tandem reaction for formation of penta-substituted cyclohexanols

A systematic study of the synthesis of halo-substituted azachalcones was conducted. During the reaction course, we obtained not only the target azachalcones, but also penta-substituted cyclohexanols, which are seldom reported in the literatures. The formation of penta-substituted cyclohexanols was dependent on equivalents of base used and reaction time. Their formation followed a tandem reaction: Claisen-Schmidt condensation, three Michael reactions, retro-aldol reaction, and intramolecular aldol cyclization.