Experiments directed towards the synthesis of anthracyclinones. VIII: Functionalization of hydroxyanthraquinones by reductive Claisen rearrangements

Gentle heating of allyloxyanthraquinones with sodium dithionite in dimethylformamide/water effects a rapid and controlled rearrangement to give high yields of 2-allylhydroxyanthraquinones.Starting from quinizarin, key intermediates for two synthetic routes to 4-demethoxydaunomycinone have been prepared from products by means of two such reductive Claisen rearrangements.