The Importance of Preliminary Orientation in [4+2]-Cycloadditions of Dienes and Dienophiles with Complex Structures

The [4+2]-cycloaddition reaction of quinopimaric acid with thebaine or β-dihydrothebaine has been performed in order to illustrate the importance of preliminary orientation of the diene and dienophile in the reaction complex stabilized due to different factors: salification was shown to be the principal factor in the orientation of the diene and dienophile in aqueous media, and steric factors were found to dominate in hydrocarbon solvents.