REDUCTIVE CYCLIZATION OF (3-OXOALKYL)-9,10-ANTHRAQUINONES AND (4-OXOALKYL)-9,10-ANTHRAQUINONES TO THE CYCLOPENTA[A]ANTHRAQUINONE AND NAPHTHACENE-5,12-DIONE SYSTEMS
K. Krohn et S. Bernhard, REDUCTIVE CYCLIZATION OF (3-OXOALKYL)-9,10-ANTHRAQUINONES AND (4-OXOALKYL)-9,10-ANTHRAQUINONES TO THE CYCLOPENTA[A]ANTHRAQUINONE AND NAPHTHACENE-5,12-DIONE SYSTEMS, Journal fur praktische Chemie, Chemiker-Zeitung, 340(1), 1998, pp. 26-33
Reductive cyclization of the 1-hydroxy-3-(3-oxoalkyl)-9,10-anthraquino
nes 2, 9 and 10 yields the angularly condensed cyclopenta[a]anthraquin
ones 3, 21 and 22a under neutral conditions (DMF/Na2S2O4). By contrast
, the linear cyclopenta[b]anthraquinone 23 is isolated from 10 applyin
g the usual alkaline Marschalk conditions (aqueous methanol, NaOH, Na2
S2O4). The linearly condensed 5,12-naphthacenequinones 24-28 of differ
ent degree of saturation are obtained in good combined yield from the
corresponding 1-hydroxy-3-(4-oxoalkyl)-9,10-anthraquinones 19 and 20 u
nder the conditions of the Marschalk reaction.