STEREOCHEMISTRY OF DIELS-ALDER REACTION . SYN-ANTI ISOMERISM

Electronic and steric factors governing syn-anti isomerism in the Diels-Alder reaction have been investigated employing 1,2,3,4,5-pentachlorocyclopentadiene as the plane asymmetric dienophile. The predominance of anti-7-chloro isomers in many cases has been ascribed to forces arising from dipole-dipole, dipole-induced dipole, and London-dispersion interactions, the predominance of endo over exo isomers to secondary orbital interactions and the lack of anti-exo isomers to steric hinderance in the transition state. © 1969, American Chemical Society. All rights reserved.