Synthesis of Novel Nitroimidazole-Pyrazole Hybrids via an Attractive Methodology of N-Alkylation of 4(5)-Nitro-1H-imidazole

Imidazole is one of the most important heterocyclic rings. This nucleus can be found in a plethora of substances in different knowledge areas such as medicinal, agrochemical, polymer, and dyestuff. N-alkylation reactions involving N − 1 atom is a remarkable tool to synthesize many imidazole derivatives which can be attached to a great variety of functional groups. In this work, we synthesized 10 new intermediates 4-chlorobutyl 1-aryl-1H-pyrazole-4-carboxylates 3(a–j) from 1-aryl-1H-pyrazole-4-carbonyl chlorides, obtained from 1-aryl-1H-pyrazole-4-carboxylic acids 4(a–j), and 4-chlorobutan-1-ol 1, generated by THF ring-opening promoted by hydrochloric acid. Compounds 3(a–j) promoted N-alkylation of 4(5)-nitro-1H-imidazole to afford the targets 4-(4-nitro-1H-imidazol-1-yl)butyl 1-aryl-1H-pyrazole-4-carboxylates 2(a–j) in 18%–85% yields.