Ring Transformation of Chromone-3-Carboxamide under Nucleophilic Conditions

Synthetic Routes to Coumarin(Benzopyrone)-Fused Five-Membered Aromatic Heterocycles Built on the α-Pyrone Moiety. Part II: Five-Membered Aromatic Rings with Multi Heteroatoms

“…The transformation of three-substituted chromone to chromeno[4,3- c ]pyrazol-4(2 H )-ones was within the scope of interest of Ibrahim’s research group [ 33 , 34 , 35 , 36 ]. In 2008, they studied the ring transformation of chromone-3-carboxylic acid ( 20 ) under the reaction with 2-cyanoacetohydrazide or the hydrazine hydrate as the nucleophile to give the corresponding chromeno[4,3- c ]pyrazol-4(2 H )-one ( 9a ) ( Scheme 7 ) [ 33 ].…”

“…In 2008, they studied the ring transformation of chromone-3-carboxylic acid ( 20 ) under the reaction with 2-cyanoacetohydrazide or the hydrazine hydrate as the nucleophile to give the corresponding chromeno[4,3- c ]pyrazol-4(2 H )-one ( 9a ) ( Scheme 7 ) [ 33 ]. Furthermore, they examined the chemical reactivity of chromone-3-carboxamide ( 21 ) towards hydrazine hydrate or phenylhydrazine and they could construct the pyrazole within the scaffold ( Scheme 7 ) [ 34 ]. Furthermore, 3-cyano-2,6-dimethyl chromone ( 23 ) was allowed to react with the nucleophile S -benzyldithiocarbazate to afford the corresponding 6,8-dimethyl chromeno[4,3- c ]pyrazol-4(2 H )-one ( 24 ) ( Scheme 7 ) [ 35 , 36 ].…”