SYNTHESIS OF HETEROANTHRACYCLINONE INTERMEDIATES: SYNTHESIS OF 6a,7,10,10a-TETRAHYDROBENZOTHIOXANTHEN-6,11,12-TRIONES

Abstract

The synthesis of some benzothioxanthentriones related to heteroanthracyclinones is reported. 1,4-Dimethoxythioxanthen-9-one was prepared by condensation of 2,2′-dithiosalicylic acid and 1,4-dimethoxybenzene which was demethylated with borontribromide to give the corresponding hydroquinone. In situ oxidation with silver oxide followed by addition of various dienes gave 6a,7,10,10a-tetrahydrobenzothioxanthen-6,11,12-triones. The compounds have been characterised on the basis of elemental and spectral studies.

Key Words:

• 2,2′-Dithiosalicylic acid
• hydroquinone
• Diels-Alder addition
• thioxanthene-9-one
• NMR
• IR