Green and Efficient Synthesis of 4‐Heteryl‐Quinolines and Their Antibacterial Evaluations

Abstract

A green and efficient synthesis of 4‐heteryl‐quinolines (9a, 9b, 9c, 9d), (10a, 10b, 10c, 10d) and (11a, 11b, 11c, 11d) has been described using PEG‐600 as a green solvent. Initially, 4‐chloro‐2‐methylquinolines (5a, 5b, 5c, 5d) on reaction with aromatic heterocyclic thiols (6), (7), and (8) using PEG‐600 at 100°C for 30–40 min resulted in (9), (10), and (11) in good yields. Alternatively, (9), (10), and (11) could also be prepared in dimethylformamide using K2CO3 as base and tetrabutylammonium bromide as phase transfer catalyst at 100°C for 1–2 h. All the compounds were synthesized and characterized by IR, NMR, mass spectroscopy, and 13C NMR analysis. All synthesized compounds were screened for their antibacterial activity against clinical strains that include Gram‐positive (Bacillus subtilis MTCC 121, staphylococcus aureus MLS‐16 MTCC 2940, Micrococcus lutes MTCC 2470, and Staphylococcus aureus MTCC 96) and Gram‐negative bacteria (Candida albicans MTCC 3017, Klebsiella planticola MTCC 530, Escherichia coli MTCC 739, and Pseudomonas aeruginosa MTCC 2453). The results revealed that compounds (9a, 9d, 10a, 10c, 11b, and 11d) exhibited significant antibacterial activity almost equal to the standard drug, that is, Ciprofloxacin.

Pyrimido[5,4‐c]quinolines: Synthesis from 3,4‐Di‐functionallized Quinoline, Reactivity and Biological Activities

“…[50] 2.10. From 3-aminomethyl-4-aminoquinolin-4(3H)-one Nasr and collaborators [13] synthesized 3-ethylaminomethyl-2methyl-4(1H)-quinolone 240a,b and its derivatives through a Mannich reaction utilizing 2-methyl-4-quinolone derivatives 239a,b, [51] Despite their structural diversity, the compounds were found to be inactive as antimalarials (Scheme 34). [13] When 1-acetylbenzotriazole 247 is heated with an excess of C 6 H 5 -NCO or p-MeC 6 H 4 NCO 18 in a sealed tube at 210 °C for 24 h, it leads to the formation of pyrimidino [5,4-c]…”

“…Nasr and collaborators [13] synthesized 3‐ethylaminomethyl‐2‐methyl‐4(1H)‐quinolone 240a , b and its derivatives through a Mannich reaction utilizing 2‐methyl‐4‐quinolone derivatives 239a , b , [51] ethylamine 15 , and paraformaldehyde in ethanol. Subsequent treatment of compounds 240a , b with POCl 3 resulted in the formation of the 4‐chloroquinolones 241a , b which were then aminated with 3‐chloroaniline 22 in HCl/EtOH, leading to the formation of the 4‐aminoquinolone derivatives 242a , b .…”

Synthesis and Functionalization of 4‐Quinolones – A Progressing Story

“…In this reaction, substituted anilines and β‐keto esters were used to prepare the 2‐aryl or 2‐alkyl quinolones 87 by an In III ‐catalyzed Conrad–Limpach cyclization reaction. Importantly, the major advantage of the protocol is the recyclability of catalyst (Scheme ) …”