S)-6-Methyl-Q-3-benzylidene-5,6-dihydropyran-2,4-diones have been synthesized from (S)-6-methyl-5.6-dihydropyran-2,4-dione through Knoevenagel condensation with an arylaldehyde followed by recrystallization from ether. The results of conjugate additions and hetero Diels-Alder reactions of these compounds including an interpretation of the observed diastemoselectivities ate described.
Previously, we have reported novel enantioselective synthetic methods by utilizing chiral 1,3dihetero-4.6~dioxocyclohexanes having an exomethylene group at the Sposition (12 and 23). The success of this method is due to fixation of the six-membered ring in a boat conformation. We have proposed novel stereoelectronic effects between hetero atoms in the acetal function and the axial substituent (Ya) at the 2position as the origin of these unique conformations.* In this pape r, we would like to report our research concerning the synthesis of the title compounds (3), in which one hetero atom of 1 and 2 is replaced by carbon and their successful utilization in enantioselective synthesis.