Polycyclic hydroxyquinones. Part 29. Regioselective reactions of 5-sulphur-substituted furan-2(5H)-one anions with naphthoquinone monoketals. Application to the synthesis of anthracyclinone precursors

Article abstract of DOI:10.1016/S0040-4020(96)01100-3

The anions of furanones 7-10, reacted with naphthoquinone monoketals 11-15 to afford exclusively the C-5 substituted Michael adducts in good yield. The annelation reactions of the anions generated from furanones 30 and 33 with naphthoquinone monoketals 11 and 12 lead to 2-sulphur-substituted 1,4-anthraquinones 32, 35 and 36. Diels-Alder reaction of the 1,4-anthraquinones 41 and 42 with (E)-1,3-bis[(trimethylsilyl)oxy]buta-1,3-diene (37) affords ABCD tetracyclic systems related to those existing in anthracyclinones.