Synthesis, Characterization, and Antibacterial and Anti-Inflammatory Activities of New Pyrimidine and Thiophene Derivatives

Abstract

Substituted[4,5]thieno[2,3-d]thiazolo[3,2-a]pyrimidin-5-one (3a-b) and pyrimidin-5(6H)-imine (3c-e) were synthesized via reaction of the starting compounds, ethyl 2-amino-substituted[b]thiophene-3-carboxylate (2a-c) and 2-amino-substituted [b]thiophene-3-carbonitrile (2d-f), respectively, with 2-bromothiazole. Synthesis of (bromo-substituted[b]thiophen-2-yl)alkanamide derivatives (4a-e) and thieno[2,3-d][1,3]oxazin-4-imine derivative (5) was accomplished via reaction of the starting compounds with bromoalkyl chloride through nucleophilic substitution; however, for the synthesis of compound 5, nucleophilic substitution was followed by nucleophilic addition to a nitrile group to form the oxazinimine ring. 1-(3-cyano-substituted[b]thiophen-2-yl)-3-(4-(trifluoromethyl)phenyl)thiourea derivatives (6a-c) were obtained via reaction of the starting compounds (2d-f) and 4-(trifluoromethyl phenyl)isothiocyanate. The lead compounds (2d-f) rapidly reacted with 4-(trifluoromethyl)benzaldehyde or 4-(2-pyridyl)benzaldehyde in acidic medium to yield compounds (7a-f) in large quantities. X-ray crystallography of compounds 4c and 7e confirmed their structures. Antimicrobial studies revealed that compound 6a was equally potent to ampicillin against Bacillus strains. Moreover, compounds 3e, 4d, and 6a possessed greater anti-inflammatory potency than that of the standard drug.