3‐Nitrocoumarin Amidines: A New Synthetic Strategy for Substituted [1]Benzopyrano[3,4‐d]imidazol‐4(3H)‐ones

Abstract

A new synthesis of substituted [1]benzopyrano [3,4-d]imidazol-4(3H)-ones, starting from 3-nitrocoumarin N-functionalized amidines 3, has been developed. When the 3-nitro-amidines 3 were treated with NaBH 4 in the presence of 10% palladium on charcoal, 2-substituted [1]benzopyrano[3,4-d]imidazol-4(3H)-ones 4 were produced. Structure elucidation of compounds 4 revealed that they exist as one of the three possible tautomeric structures (i.e., 4dα). Alkylation of 4d to give 6, as well as NOE experiments on 6

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

“…Trimarco’s research group developed a new method to synthesize substituted [1]benzopyrano[3,4- d ]imidazol-4(3 H )-ones bearing hydrogen or alkyl groups on N-3, and alkyl or amino substituents on C-2 in good yields [ 45 ]. 2-Alkyl-[1]benzopyrano[3,4- d ]imidazol-4(3 H )-ones 57 were obtained from acetamidines 56 carrying a 3-nitrocoumarin group at N-1 by reduction with sodium borohydride/palladium 10% ( Scheme 15 ) [ 45 ]. Benzopyranoimidazoles 58 of an amino substituent on C-2 were obtained by refluxing 56 in excess of triethyl phosphite ( Scheme 15 ) [ 45 ].…”

“…2-Alkyl-[1]benzopyrano[3,4- d ]imidazol-4(3 H )-ones 57 were obtained from acetamidines 56 carrying a 3-nitrocoumarin group at N-1 by reduction with sodium borohydride/palladium 10% ( Scheme 15 ) [ 45 ]. Benzopyranoimidazoles 58 of an amino substituent on C-2 were obtained by refluxing 56 in excess of triethyl phosphite ( Scheme 15 ) [ 45 ].…”

Efficient synthesis of 2-substituted 1-phenylchromen[3,4-d]imidazol-4(1H)-ones with possible anti-inflammatory activity

“…18 There are also a few known 2,3-disubstituted imidazolo [3,4-d]coumarins. The 3-methyl-2-propylimidazolo [3,4-d]coumarin has been prepared by the methylation of 2-propylimidazolo [3,4-d]coumarin, 19 while the 3-chloroethyl-2-propylimidazolo [3,4-d]coumarin was obtained by us during the chloromethylation of the same starting compound. 20 3-Alkyl-2-(morpholin-4yl)imidazolo [3,4-d]coumarins were synthesized from 4-[(1-morpholin-4-yl)amino]-3-nitrocoumarins by heating at reflux in excess of triethyl phosphite.…”

“…20 3-Alkyl-2-(morpholin-4yl)imidazolo [3,4-d]coumarins were synthesized from 4-[(1-morpholin-4-yl)amino]-3-nitrocoumarins by heating at reflux in excess of triethyl phosphite. 19 There are only two routes to mono-1-N-substituted fused imidazolocoumarins: (i) Construction of the pyranone ring, for 1-substituted chromeno [3,4-d]imidazol-4(1H)-ones, by cyclization of alkyl 5-(2hydroxyphenyl)-1H-imidazole-4-carboxylates in aqueous sulfuric acid under heating 11 or in the presence of base under MW irradiation; 21 and, (ii) construction of the imidazole ring, for 1-phenyl or 1-alkyl substituted chromeno [3,4-d]imidazol-4(1H)-ones, by the reaction of 3-amino-4-phenylamino-or 4-alkylaminocoumarin in boiling formic acid. 15 Previously, our group developed an efficient synthesis of 2-substituted imidazolocoumarins starting from 4-amino-3-nitrocoumarin.…”

Indium(III) Chloride Catalyzed One-Pot Multicomponent Synthesis of Chromenone- and Quinolone-Annulated Imidazole Derivatives

“…This new class of compounds and their derivatives may be of interest to pharmacologists and medicinal chemists. Close analogues, chromeno [4,3-d]imidazol-4(3H)-one derivatives, were synthesized by Trimarco et al 13 via a multistep synthesis, but chromeno[5, 6-d]imidazol-7(3H)-one and 3,6dihydro-7H-imidazo[4,5-f]quinolin-7-one are still less investigated and to the best of our knowledge so far there is only one report 14 of chromeno[5, 6-d]imidazol-7(3H)-one derivatives by the reaction of 5,6-diamino-2H-chromen-2-one, benzoic acid, and polyphosphoric acid under reflux conditions; the methodology suffers from the requirement for strongly acidic conditions. Hence the synthesis of chromeno[5, 6-d]imidazol-7(3H)-one and 3,6-dihydro-7H-imidazo [4,5-f]quinolin-7-one derivatives by a simple, step-economic, and less hazardous methodology is still important and requires further investigation.…”