Synthesis of Tetrahydrobenzothieno[ 2,3-d]pyrimidine and Tetrahydrobenzothieno[3,2-e]- [1,2,4]triazolo[4,3-c]pyrimidine Derivatives as Potential Antimicrobial Agents

Five series of tetrahydrobenzothieno[2,3-d]pyrimidine and tetrahydrobenzothienotriazolopyrimidine derivatives have been synthesized namely: 4-(substituted amino)-5,6,7,8-tetrahydro[1]benzothieno[2,3-d]pyrimidines 4a–d, 4-substituted (methylidenehydrazino)-5,6,7,8-tetrahydro[1]benzothieno- [2,3-d]pyrimidines 6a–c, 4-(3,5-disubstituted pyrazol-1-yl)-5,6,7,8-tetrahydro- [1]benzothieno[2,3-d]pyrimidines 7a,b, 3-substituted-8,9,10,11-tetrahydro- [1]benzothieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidines 8a,b, N-(phenyl or 4-substituted phenyl)-2-(8,9,10,11-tetrahydro[1]benzothieno[3,2-e][1,2,4]- triazolo[4,3-c]pyrimidin-3-ylsulfanyl)acetamides 10a–c. Preliminary antimicrobial testing revealed that compounds 4a and 10b were the most active among the tested compounds against C. albicans showing IZ = 22 mm and MIC = MBC = 31.25 μg/ml, with no significant antibacterial activity. Compounds 6b and 6c showed the highest antibacterial activity against S. aureus (IZ = 21 mm, MIC = 62.5 μg/ml, MBC = 125 μg/ml for 6b; IZ = 21 mm, MIC = MBC = 125 μg/ml for 6c). Compounds 4c and 6c showed the highest antibacterial potency against P. aeruginosa among the tested compounds (IZ = 19–20 mm, MIC = MBC = 62.5 μg/ml). None of the tested compounds showed significant antibacterial activity against E. coli.