New Cyclopenta[4',5']pyrido[3',2':4,5]thieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidines and Cyclopenta[4',5']pyrido[3',2':4,5]thieno[2,3-e][1,2,4]triazolo[1,5-c]pyrimidines: Synthesis and Antimicrobial Activities

Background and Objective: Continuing our researches in the field of heterocyclic chemistry, the study on the chemical properties of compounds simultaneously containing different heterocycles such as fused thieno[2,3-b]pyridines, fused triazoles has been carried out. Moreover, their possible antimicrobial activity against some gram-positive and gram-negative bacilli strains has been evaluated. Methods: Starting from the hydrazino derivative of cyclopenta[4',5']pyrido[3',2':4,5]thieno[3,2-d]pyrimidines 1 by reflux with triethyl orthoformate or formic acid, some substituted isomeric cyclopenta[4',5'] pyrido[3',2':4,5] thieno[2,3-e][1,2,4]triazolopyrimidines 2 and 3 have been synthesized. Results: 10-Alkyl(aryl)-8,9-dihydro-7H-cyclopenta[4',5']pyrido[3',2':4,5]thieno[2,3-e] [1,2,4]triazolo[4,3-c] pyrimidines 2 and 10-isobutyl-3-(methylthio)-8,9-dihydro-7H-cyclopenta[4',5']pyrido[3',2':4,5]thieno[2,3-e] [1,2,4]t riazolo[4,3-c]pyrimidine 5 gave the Dimroth rearrangement in both basic and acidic media. By reaction with formic acid or with triethyl orthoformate, 4-alkyl-7-hydrazino-9-(methylthio)-2,3-dihydro-1H-cyclopenta[ 4',5'] pyrido[3',2':4,5]thieno[3,2-d]pyrimidines 13 furnished 10-alkyl-5-(methylthio)-8,9-dihydro-7Hcyclopenta[ 4',5'] pyrido[3',2':4,5]thieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidines 14. In turn, compounds 14 gave with potassium carbonate 10-isobutyl-5-(methylthio)-8,9-dihydro-7H-cyclopenta[4',5']pyrido[3', 2':4,5]thieno [2,3-e][1,2,4]tria-zolo[1,5-c]pyrimidine 15 and with amines 10-alkyl-8,9-dihydro-7H-cyclopenta[4', 5']pyrido [3',2':4,5]thieno[2,3-e][1,2,4]triazolo [1,5-c]pyrimidin-5-amines 16 by contemporary substitution of the SCH3 group with amines and Dimroth rearrangement. Conclusion: Several cyclopenta[4',5']pyrido[3',2':4,5]thieno[2,3-e][1,2,4]triazolopyrimidines have been synthesized. The study of their reactivity evidenced that Dimroth rearrangement in case of 10-alkyl(aryl)-8,9- dihydro-7H-cyclopenta[4',5']pyrido[3',2':4,5]thieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidines 2 as well as 10-isobutyl-3-(methylthio)-8,9-dihydro-7H-cyclopenta[4',5']pyrido[3',2':4,5]thieno[2,3-e][1,2,4]triazolo[4,3-c] pyrimidine 5 occurred in both acidic and basic media. The biological activity of the synthesized compounds against some gram-positive bacteria and gram-negative bacilli strains was examined evidencing some interesting relation between the structure of the examined compounds and their antimicrobial activity.