Process for aromatizing 19-norandrost-4-en-3-ones to estra-1,3,5(10)-trienes

Process for CuBr2-mediated aromatization of 19-norandrost-4-en-3-ones of the general formula (II) to estra-1,3,5(10)-trienes of the general formula I

• where, in formula (II) and formula (I), each R is independently any chemically stable radical, characterized in that the aromatization is effected in the presence of at least one electron-rich, unsaturated organic additive of the general formula (Z)
• where
• R1, R2, R3, R4 are each independently hydrogen, a C1-C6-alkyl, C2-C6-alkenyl, C1-C6-alkoxy or C2-C6-alkenoxy radical or a C6-aryl ring or C6-aryloxy ring, with the proviso that at least one radical of R1, R2, R3, R4 is not hydrogen,
• or
• R1 and R2, together with the carbon atoms of the double bond, form a C6-aromatic optionally mono- or polysubstituted identically or differently by hydroxyl, a C1-C6-alkoxy radical and/or C1-C6-alkyl radical, a C3-C7-cycloalkene, a monocyclic heteroaromatic or an unsaturated heterocycle optionally additionally substituted by R3 and R4, where R3 and R4 are each independently a C1-C6-alkyl, C2-C6-alkenyl, C1-C6-alkoxy or C2-C6-alkenoxy radical, or a C6-aryl ring or C6-aryloxy ring,
• and enantiomers and diastereomers thereof.