Synthesis of 6-substituted thieno[3,2-b]pyrroles

Synthesis of Heterocyclic Compounds Possessing the 4H-Thieno[3,2-b]Pyrrole Moiety

“…2 The general synthetic approach to the substituted alkyl thieno- [3,2-b]pyrrole-5-carboxylates includes transformation of compounds II into numerous derivatives III under treatment of different reagents. For example, the reported works describe synthesis of alkyl thieno [3,2-b]pyrrole-5-carboxylates III with the following substituents: 2-formyl, 11,19 2-acetyl, 11 2-bromo, 28 2,6-dibromo, 11 2,3,6-tribromo, 11 2-nitro, 28 2,6-dinitro, 28 3-formyl, 19 4-benzyl, 10 4-(2-nitrobenzyl), 11,34 6-dimethylaminomethyl, 11 6-(1-piperidinylmethyl), 13 6-cyanomethyl, 11 6-formyl, 11,37 2-methyl-3-acyl, 35-37 2-methyl-3,6-diacyl, 35,37 2-methyl-4-(2-oxopropyl), 38 and 2-methyl-4-(2-oxo-2-phenylethyl). 38 Some of the mentioned esters were then hydrolyzed to the corresponding acids, which usually served as convenient starting materials in subsequent transformations, for example, for synthesis of the corresponding amides 13,18 or decarboxylated products.…”

“…For example, the reported works describe synthesis of alkyl thieno [3,2-b]pyrrole-5-carboxylates III with the following substituents: 2-formyl, 11,19 2-acetyl, 11 2-bromo, 28 2,6-dibromo, 11 2,3,6-tribromo, 11 2-nitro, 28 2,6-dinitro, 28 3-formyl, 19 4-benzyl, 10 4-(2-nitrobenzyl), 11,34 6-dimethylaminomethyl, 11 6-(1-piperidinylmethyl), 13 6-cyanomethyl, 11 6-formyl, 11,37 2-methyl-3-acyl, 35-37 2-methyl-3,6-diacyl, 35,37 2-methyl-4-(2-oxopropyl), 38 and 2-methyl-4-(2-oxo-2-phenylethyl). 38 Some of the mentioned esters were then hydrolyzed to the corresponding acids, which usually served as convenient starting materials in subsequent transformations, for example, for synthesis of the corresponding amides 13,18 or decarboxylated products. 18 Syntheses of several annulated heterocycles possessing the 4H-thieno [3,2-b]pyrrole moiety have been previously described, for example, thieno [2,3-b]indolizine IV, 39 5,6,7,8tetrahydro-4H-thieno[3′,2′:2,3]pyrrolo [4,5-c]pyridine V, 14 8-oxo-5,6,7,8-tetrahydrothieno[2′,3′:4,5]pyrrolo [1,2-a]pyrazine VI, 38 3H,4H,5H-thieno[3′,2′:2,3]pyridazin-4-ones VII, 11,37 and 5-oxo-6,11-dihydro-5H-benzo[e]thieno[2′,3′:4,5]pyrrolo-[1,2-a] 1,4 diazepine VIII.…”

“…The parent heterocycle I was synthesized in 1957 by the reductive cyclization of 3-nitro-2-thienylpyruvic acid, followed by decarboxylation of the product, namely, thieno[3,2- b ]pyrrole-5-carboxylic acid, and also by the reduction of 2 H ,3 H -thieno[3,2- b ]pyrrol-3-one obtained via cyclization of pyrrole-3-thioacetic acid . The general synthetic approach to the substituted alkyl thieno[3,2- b ]pyrrole-5-carboxylates includes transformation of compounds II into numerous derivatives III under treatment of different reagents. − For example, the reported works describe synthesis of alkyl thieno[3,2- b ]pyrrole-5-carboxylates III with the following substituents: 2-formyl, , 2-acetyl, 2-bromo, 2,6-dibromo, 2,3,6-tribromo, 2-nitro, 2,6-dinitro, 3-formyl, 4-benzyl, 4-(2-nitrobenzyl), , 6-dimethylaminomethyl, 6-(1-piperidinylmethyl), 6-cyanomethyl, 6-formyl, , 2-methyl-3-acyl, − 2-methyl-3,6-diacyl, , 2-methyl-4-(2-oxopropyl), and 2-methyl-4-(2-oxo-2-phenylethyl) . Some of the mentioned esters were then hydrolyzed to the corresponding acids, which usually served as convenient starting materials in subsequent tran...…”