Abstract
Direct one-pot base-promoted conjugate addition–elimination of 6,8-dibromo-4-chloroquinoline-3-carbaldehyde with methyl mercaptoacetate and subsequent cyclization afforded methyl [(6,8-dibromothieno[3,2-c]quinoline)]-2-carboxylate. The latter undergoes Suzuki-Miyaura cross-coupling with arylboronic acids to yield exclusively the corresponding alkyl [(6,8-diarylthieno[3,2-c]quinoline)]-2-carboxylates,. The cytotoxicity of the prepared compounds was evaluated against the human breast cancer cell line MCF-7 using the MTT assay. The effects of compounds 2, 3c and 4d on cell kinetics were further determined using the xCELLigence Real Time Cell Analysis (RTCA) system. In both the MTT assay and Real Time Cell Analysis, the compounds inhibited cancer cell growth in a dose- and time-dependent manner. Furthermore, on the basis of the calculated LC50 values, the compounds compared favourably with nocodazole, a well-established anticancer drug.
Highlights
The synthesis of thieno[3,2-c]quinoline-based compounds continues to attract a great deal of attention in research because of their rich biological activities and excellent pharmacological properties
We isolated by filtration a single product which was characterized using a combination of 1H-NMR and IR spectroscopic techniques as well as mass spectrometry as methyl [(6,8dibromothieno[3,2-c]quinoline)]-2-carboxylate 2
We took advantage of the bromine atoms to investigate the reactivity of compound 2 in palladium catalyzed Suzuki-Miyaura cross-coupling with arylboronic and arylvinylboronic acids
Summary
The synthesis of thieno[3,2-c]quinoline-based compounds continues to attract a great deal of attention in research because of their rich biological activities and excellent pharmacological properties. This moiety is widely distributed in biologically important compounds including antibacterial [1], anticancer [2] and anti-inflammatory agents [3]. A series of substituted 2,4-dimethyl-thieno[3,2-c]quinolones was previously prepared via intramolecular cyclization and subsequent aromatization of 3-(2-chloroprop-2en-1-yl)- and 3-(2-oxopropyl)-2-methylquinolin-4-thiols [6]. A single-pot synthesis of thieno[3,2-c]quinolin-4(5H)-ones involving successive m-chloroperbenzoic acid-mediated oxidation of 4-(4'-aryloxybut-2'-ynyl)thioquinolin-2(1H)-ones in chloroform at 0–5 °C followed by heating and treatment with 20% KOH (aq) has been described in the literature [8]. A one-pot conjugate addition-elimination of the analogous 2,4-dichloroquinoline-3-carbonitrile with ethyl mercaptoacetate previously afforded ethyl 3-amino-4-chlorothieno[3,2-c]quinoline-2-carboxylates [4,10]
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