Anthraquinone annulation

Both naphthoquinones and anthraquinones bearing annulated benzothiazine rings, as illustrated by compounds (4.16), (4.17) and (4.18), absorb in the near-lR. Unfortunately, the naphthoquinones tend to have low stability and products from both ring systems are strongly coloured, limiting their areas of application. 

The annulation of these oxidation products 9, 10 with the anion of 3-cyanophthalide 105 affords access to a range of anthraquinones 106 ° (equation 43). 

The palladium-catalyzed annulation of arynes, derived from 2-(trimethylsilyl)phenyl triflate, by 2-halobenzaldehydes provides variably substituted fluoren-9-ones in good yields (eq 4). Catalytic dicobalt octacarbonyl under CO pressure furnishes anthraquinones in the presence of the ar5me derived from 2-(trimethylsilyl)phenyl triflate. ... 

---