SYNTHESES OF ANTHRACENONES .3. REVISED PREPARATIVE ROUTE TO 10-BENZOYL-1,8-DIHYDROXY-9(10H)-ANTHRACENONES

The acylation of anthralin (1,8-dihydroxy-9(10H)-anthracenone) with ac etylsalicylic acid chloride in toluene and collidine was found to give the O-acylated product, rather than 10-(acetylsalicyl)-anthralin. A p rocedure is described for benzoylation of anthralin in the 10-position which involves reaction of 1,8-diacetoxy-9(10H)-anthracenone with ben zoyl chloride and sodium hydride in THF followed by hydrolysis of an i ntermediate enol ester. Furthermore, when benzoyl chloride and DMF wer e used for the acylation of anthralin, a Vilsmeier-type reaction was o bserved leading to a novel enamine derivative of anthralin which was h ydrolyzed or benzoylated to an enol or enol ester, respectively.