The regioselective alkylation of 1, 4, 5-trihydroxy-9, 10-anthraquinone via reaction of its leuco compound is significant for the synthesis of anthracyclinones. In the presence of pyrrolidine in toluene solution, the leuco compound 3 selectively forms the 4-pyrrolidino enamine 11, which undergoes deamination to give 1, 5-dihydroxy-9, 10-anthraquinone. If an aldehyde is added, however, the enamine is alkylated, eventually yielding the 3-alky 1-1, ...
