No abstract

In the pharmaceutical industry, boronic acid and esters play an important role in API-based synthesis. The most efficient way of preparing various active agents is palladium-catalyzed Suzuki–Miyaura borylation reactions. Herein, we report the formation of dimerization product [6,6′-biimidazo[1,2-a]pyridine]-2,2′-dicarboxamide derivatives 7a–j from 6-bromoimidazo[1,2-a]pyridine-2-carboxylate by employing the same conditions. A regioselective borylation of ethyl 6-bromoimidazo[1,2-a]pyridine-2-carboxylate (3) was examined for the formation of ethyl 6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)imidazo[1,2-a]pyridine-2-carboxylate (4a) but it was found to be directed towards the dimerization product 5. The nitrogen-rich system was incorporated into potential anti-cancer and anti-TB agents through acid amine coupling reactions between acid 6 and various amines (dialkyl/cyclic sec./tert.) to form the final adducts 7. Five derived scaffolds were identified as moderately active in TB activity against the H37Rv strain, while two compounds were found to be particularly potent in NCI-60 anti-cancer screening in nine cancer panels.

An efficient, facile and regioselective route has been utilized for the synthesis of novel series of 5-(5-amino-1H-pyrazol-3-yl)-1,3-dimethyl-1,3-dihydro-2Hbenzo[d]imidazol-2-one derivatives (5a-l). The methyl 3,4-diaminobenzoate (1) used CDI/DMF system for the cyclization to benzimidazolone followed by Nmethylation and next ACN/n-BuLi media at À70 C to afford high yielded key intermediate, 3-(1,3-dimethyl-2-oxo-2,3-dihydro-1H-benzo[d]imidazol-5-yl)-3-oxopropanenitrile (4). The final adducts synthesis involved catalytic optimization to generate 5-amino pyrazole-based adducts (5a-l) rather than 3-amino pyrazole (6a-l) are discussed. Chromatographic and spectral techniques ( 1 H & 13C NMR, LC-MS, elemental analysis) confirmed the newly synthesized structures and were evaluated for antioxidant activity using DPPH free radical scavenging assay. The entire compounds showed extra (higher) potency against used standard ascorbic acid except 5j (2-F Ph substituent) while, 5c (ÀEt substitution) was found to be most potent among others.