Experiments directed towards the synthesis of anthracyclinones. XXXII - Synthesis of anthraquinone aldehydes

Syntheses of C2 anthraquinone aldehydes from the commercially available ant hrarufin (1) have been investigated. A synthesis of the keto aldehyde (2) i n nine steps and 73% overall yield was achieved. Syntheses of (2) exploitin g selective oxidations of either a C-bound allyl group by Wacker oxidation to introduce the methyl keto functionality or of a C-bound prop-1-enyl moie ty by dihydroxylation and oxidative cleavage to generate the C2 formyl grou p were also developed. The aldehyde (27) was synthesized in seven steps and in 81% overall yield from (1), and syntheses of the phenolic aldehydes (33 ), (34), and (35), the C1 benzyloxy aldehyde (36) and the anthracene aldehy de (37) were also developed.