in tetrahydrofuran treating Fe-complex with Br2 at -78°C (mixture turning red); allowing to reach ambient temp.; removing solvent in vac.; suspending in ether, centrifusion, removing ether in vac.; chromy. under Ar (silica gel, 1:5-EtOAc/hexane);
Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science (English Translation), , vol. 30, # 12 p. 2347 - 2349
Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, , # 12 p. 2815 - 2818
