The synthesis of naphthothiopyranopyranones and naphthothiopyranopyranthiones

The synthesis of fused tetracyclic naphthothiopyranopyranones from dihydronaphthothiopyranones I or II has been studied. Compounds I or II have been cyclised in good yield to the corresponding dioxaborin difluoride complexes III, IV, XIII and XIV by treatment with acetic or propionic anhydride and boron trifluoride etherate. These complexes and the Vilsmeier reagent reacted to produce fused tetracyclic 3-substituted naphthothiopyranopyranones V, VI, XV or XVI . The reaction of dioxaborin difluoride complexes III or IV with dimethylthioformamide (DMTF) afforded dimethylaminovinyldioxaborin difluoride complexes IX or X . Treatment of IX or X with hydrochloric acid solution gave naphthothiopyranopyranones VII or VIII . The reaction of VII, VIII, XV or XVI with DMTF/acetic anhydride yielded new products, which was identified as naphthothiopyranopyranthions XI, XII, XVII or XVIII .