Ga. Tolstikov et al., THE IMPORTANCE OF PRELIMINARY ORIENTATION IN [4-CYCLOADDITIONS OF DIENES AND DIENOPHILES WITH COMPLEX STRUCTURES(2]), Mendeleev communications, (2), 1994, pp. 60-62
The [4+2]-cycloaddition reaction of quinopimaric acid with thebaine or
beta-dihydrothebaine has been performed in order to illustrate the im
portance of preliminary orientation of the diene and dienophile in the
reaction complex stabilized due to different factors: salification wa
s shown to be the principal factor in the orientation of the diene and
dienophile in aqueous media, and sterile factors were found to domina
te in hydrocarbon solvents.