Synthesis of Functionalized H-[1]Benzopyrano[2,3-b]pyridines by the Friedlander Approach: Antimycobacterial and Antimicrobial Profile

A series of functionalized H-[1]benzopyrano[2,3-b]pyridine derivatives were synthesized by the Friedlander reaction of 2-amino-4-oxo-4H-chromene-3-carbonitriles 1 with malononitrile, ethyl cyanoacetate, or acetophenone (Scheme). The synthesized compounds 24 were screened for their in vitro activity against antitubercular, antibacterial, and antifungal species (Fig., Table). Among the synthesized compounds, 3c and 4f were the most active with 99% inhibition against Mycobacterium tuberculosis H37Rv, while compounds 2f, 3f, and 4d exhibited 69%, 63%, and 61% inhibition, respectively. The 4-amino-7,9-dibromo-1,5-dihydro-2,5-dioxo-2H-chromeno[2,3-b]pyridine-3-carbonitrile (3b) showed the most potent antibacterial activity against Escherichia coli and Pseudomonas aeruginosa. Several chromeno[2,3-b]pyridine derivatives showed equal or more potency against Staphylococcus aureus and Candida albicans.