31. Stereoselective Syntheses of Benz[f]isoindoline-Derivatives by Intramolecular Cycloadditions of Styrenes to Olefins
    Oppolzer, W.; Achini, R.; Pfenninger, E.; Weber, H. P.
    Helv. Chim. Acta 1976, 59, 1186-1202

The N-allyl-N-cinnamyl amide 10 undergoes thermal cyclization to a 2:1-mixture of the trans- and cis-benz(f)isoindolines 11a and 12a. By comparison, the thermolysis of the corresponding bis-cinnamylamide 14 proceeds in a highly stereoselective manner to give the cis-fused[4+2]-adduct 16a. Similarly, the trans-fused stereoisomeric adducts 30a and 31a were obtained with high stereochemical control on heating the N-allyl-N-diphenylallyl amide 28. The thermal transformations 4 → 5+6a and 17 → 18a+20a show the competitive formation of [2+2]-adducts. An alternative approach to (substituted) benz[f]isoindolines 16via the all-cis-isomer 24a has been developed. The described structures have been assigned on the basis of spectral evidence, chemical correlations and by X-ray-diffraction study of the isomer 16b. These results illustrate the utility of substituent interactions in order to direct intramolecular cyclo-additions at will towards eitherendo- or exo-products.

DOI : 10.1002/hlca.19760590421