Linear and Angular Heteroannulated Pyridines Tethered 6-Hydroxy-4,7-Dimethoxybenzofuran: Synthesis and Antimicrobial Activity

Abstract

2-Chloropyridine-3-carbonitrile derivative <b>1</b> was utilized as a key precursor to build a series of linear and angular annulated pyridines linked to a 6-hydroxy-4,7-dimethoxybenzofuran moiety. Reaction of substrate <b>1</b> with various hydrazines afforded pyrazolo[3,4-<i>b</i>]pyridines. Treatment of substrate <b>1</b> with 1,3-<i>N</i>,<i>N</i>-binucleophiles including 3-amino-1,2,4-triazole, 5-amino-1<i>H</i>-tetrazole, 3-amino-6-methyl-1,2,4-triazin-5(4<i>H</i>)-one and 2-aminobenzimidazole produced the novel angular pyrido[3,2-<i>e</i>][1,2,4]triazolo[4,3-<i>a</i>]pyrimidine, pyrido[3,2-<i>e</i>][1,2,4]tetrazolo[1,5-<i>a</i>]pyrimidine, pyrido[3',2':5,6] pyrimido[2,1-<i>c</i>][1,2,4]triazine and benzo[4,5]imidazo[1,2-<i>a</i>]pyrido[3,2-<i>e</i>]pyrimidine, respectively. Reaction of substrate <b>1</b> with 1,3-<i>C</i>,<i>N</i>-binucleophiles including cyanoacetamides and 1<i>H</i>-benzimidazol-2-ylacetonitrile furnished 1,8-naphthyridines and benzoimidazonaphthyridine. Moreover, reacting substrate <b>1</b> with 5-aminopyrazoles gave pyrazolo[3,4-<i>b</i>][1,8]naphthyridines. Finally, reaction of compound <b>1</b> with 6-aminouracils as cyclic enamines yielded pyrimido[4,5-<i>b</i>][1,8]naphthyridines. Some of the synthesized products showed noteworthy antimicrobial efficiency against all types of microbial strains. Structures of the produced compounds were established using analytical and spectroscopic tools.