Synthesis and reactions of halo‐, nitro‐, and arylazo‐substituted 3‐acetyltropolones. Formation of heterocycle‐fused troponoid compounds

Abstract

Abstract 3‐Acetyltropolone ( 1 ) reacted with bromine, iodine, and nitric acid to afford respectively 3‐acetyl‐5,7‐di‐bromotropolone ( 2 ), 3‐acetyl‐7‐iodotropolone ( 3 ), and 3‐acetyl‐5‐nitro‐ ( 4 ) and 3‐acetyl‐5,7‐dinitrotropolone ( 5 ). Azo‐coupling reactions of 1 gave 3‐acetyl‐5‐arylazotropolones 7a‐f. The Schmidt reactions of 2 and 3 gave respectively 5,7‐dibromo‐ ( 9 ) and 7‐iodo‐2‐methyl‐8 H ‐cyclohept[ d ]oxazol‐8‐one ( 10 ), while 4 gave 3‐acetamido‐5‐nitrotropolone ( 11 ). Compounds 2 and 4 reacted with hydroxylamine to give 3‐methyl‐8 H ‐cyclohept[ d ]isoxazol‐8‐ones 12 and 13. The reactions of 2 , 3 , and 4 with hydrazine gave 3‐methyl‐1,8‐dihydrocycloheptapyrazol‐8‐ones 15 , 16 , and 17.