Medium-Ring Systems. 5. Synthesis and Base-Catalyzed Isomerizations of Medium-Ring Cycloalkenones with Electron-Withdrawing Substituents

Article abstract of DOI:10.1021/jo00190a017

Medium-ring 3-cycloalkenones with electron-withdrawing substituents at the 3-position have been synthesized and subjected to base-catalyzed isomerizations.In a given ring size in the seven- and eight-membered carbocycles, the substituents studied caused similar shifts in the equilibria toward the 3-cycloalkenones relative to the unsubstituted cases.Steric effects of the substituents are therefore not significant.As the ring size is increased, the preference for the 3-cycloalkenone becomes more pronounced.In the nine- and ten-membered systems, an additional equilibrium involving formation of 4-cycloalkenones appears.Decreased effectiveness of conjugative interactions in endocyclic dienolates and in 2-cycloalkenones with increasing ring size is suggested.