A facile regioselective synthesis of novel spiro-thioxanthene and spiro-xanthene-9',2-[1,3,4]thiadiazole derivatives as potential analgesic and anti-inflammatory agents.

The 1,3-dipolar cycloaddition of nitrile imines to 9H-thioxanthone-9-thione and 9H-xanthone-9-thione afforded novel spiro-thioxanthene-9',2-[1,3,4]thiadiazoles 6a-g and spiro-xanthene-9',2-[1,3,4]thiadiazoles 7a-g in good yields. Some of the newly synthesized compounds were tested for anti-inflammatory and analgesic activities comparable to ibuprofen. Compounds 6a,d,e and 7a,d,e showed significant activity compared to standard drug. The toxicity studies revealed that neither death nor other behavioral or toxicological changes were observed on rats up to a dose as high as 200 mg/kg.