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

Abstract

Abstract 3‐Cinnamoyltropolone ( 1 ) reacted with bromine to afford 7‐bromo‐ ( 2 ), 5,7‐dibromo‐3‐cinnamoyltropolone ( 3 ), and 6,8‐dibromo‐4,9‐dihydrocyclohepta[ b ]pyrane‐4,9‐dione ( 4 ) according to amount of the reagent. Iodination and nitration of 1 gave respectively 7‐iodo‐ ( 5 ) and 5‐nitro‐3‐cinnamoyltropolone ( 6 ). Azo‐coupling reactions gave 5‐arylazo‐3‐cinnamoyltropolones 7a‐f . Compounds 1, 2, 3 and 5 reacted with hydroxylamine to give 3‐styryl‐8 H ‐cyclohept[ d ]isoxazol‐8‐ones 10‐13 , while 6 and 7a gave 5‐nitro‐3‐styryl‐8 H ‐cyclohept[ d ]‐isoxazol‐8‐one oxime ( 14 ) and 2‐cinnamoyl‐7‐methoxy‐4‐phenylazotropone ( 15 ), respectively. The reactions of 1,3 , and 5 with phenylhydrazine gave 3‐styryl‐1,8‐dihydrocycloheptapyrazol‐8‐ones 16‐19 .