Article révisé par les pairs
Résumé : Treatment of dl‐1‐formyl[6]helicene (1) with the ylid of (EtO)2P(O)CH2CO2Et in boiling C6H6 gave a mixture of two dl epimeric cycloaddition products: trans‐2a (80%) and cis‐2b (12%) An X‐ray diffraction study (Van Meerssche et al. [2]) fully confirmed the structure and the stereochemistry assigned to the most abundant stereoisomer 2a by UV., 1H‐INDOR, NOE and catalytic hydrogenation of the non‐benzenoid double bonds. Copyright © 1975 Verlag GmbH & Co. KGaA, Weinheim