A facile synthesis of Methyl-2-(N-ethyl-N-phenylamino)naphthyridine-3-carboxylates

Anantoju, Kishore Kumar; Tharikoppula, Giri; Eppakayala, Laxminarayana; Chary, M. Thirumala

doi:10.1016/j.ijcas.2013.07.008

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“…We have synthesized these compounds by using carbamates. In continuation of our earlier reports [16][17][18][19][20][21][22][23][24] on synthesis of naphthyridine derivatives, we herein report a novel approach to synthesize 1-[3-(1,8-naphthyridin-2-yl)phenyl]-3-arylurea derivatives.…”

Section: Introductionmentioning

confidence: 84%

Synthesis and Antimicrobial Activity of Novel 1-[3-(1,8-Naphthyridin-2-yl)phenyl]-3-arylurea Derivatives

Bhasker¹,

Satyanarayana²,

Latha³

et al. 2018

Asian J. Chem.

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Asian Journal of Chemistry; Vol. 30, No. 4 (2018), [771][772][773][774] and only diagnostic and/or intense peaks are reported. 1H NMR spectra were recorded in DMSO-d 6 with a Varian Mercury plus 400 MHz instrument. Signals due to residual protonated solvent ( 1 H NMR) served as the internal standard. All the chemical shifts were presented in δ (ppm) using TMS as an internal standard. The 1 H NMR chemical shifts and coupling constants were determined assuming first-order behaviour. Mass spectra were recorded with a PE Sciex model API 3000 instrument. All the reactions were carried out under argon atmosphere.Biological assay: The synthesized compounds were dissolved in dimethyl sulphoxide at 30 µg/µL concentration (standard antibacterial drug, ampicilline was used as the reference antibiotic) and tested against Gram-negative strains of Escherichia coli, Klebsiella pneumonia and Gram-positive strains of Staphylococcus aureus and Bacillus subtilis using agar well diffusion method. Activities were determined by zones showing complete inhibition (mm). Growth inhibition was calculated with reference to positive control. All the samples were taken in triplicates.Synthesis of 2-(3-Nitrophenyl)-1,8-naphthyridine (3): To a stirred solution of 2-aminonicotinaldehyde (1 g, 8.18 mmol) in ethyl alcohol (20 mL) was added 1-(3-nitrophenyl)-ethanone (1.48 g, 9.00 mmol) and piperidine (2.09 g, 24.56 mmol) at room temperature and refluxed for 16 h. After completion of the reaction (monitored by TLC), the mixture was concentrated under reduced pressure and the crude product washed with 10 % dichloromethane in diethyl ether to afford 2-(3-nitrophenyl)-1,8-naphthyridine (3).Off Synthesis of 3-(1,8-naphthyridin-2-yl)aniline (4): To a stirred suspension of raney nickel (0.92 g, 10.75 mmol) in ethyl alcohol (20 mL) was added 2-(3-nitrophenyl)-1,8-naphthyridine (1 g, 3.58 mmol) and hydrazine hydrate (80 %) (0.54 g, 10.75 mmol) at room temperature and stirred at room temperature for 3 h. After completion of the reaction (monitored by TLC), the mixture was filtered through celite pad and the filtrate was concentrated under reduced pressure. The crude product was washed with 10 % dichloromethane in diethyl ether to afford 3-(1,8-naphthyridin-2-yl)aniline (4).IR ( δ 159. 7, 155.4, 153.7, 149.1, 138.8, 138.2, 137.1, 129.3, 121.8, 121.4, 119.5, 115.8, 115.2, 112.7; 222.19 (M+1). Synthesis of phenyl phenylcarbamate derivatives (5a-q):To a stirred solution of anilines (3.29 mmol) in dichloromethane (6 mL) was added triethylamine (9.89 mmol) at room temperature and stirred at room temperature for 10 min and added aryl chloro formate (4.93 mmol) at 0 °C and stirred at room temperature for 2 h. The reaction mixture was concentrated under reduced pressure and the crude material washed with 10 % diethyl ether in pentane to afford the pure compounds. Without further purification used for next step. Yields of the products varied between 65 to 85 %.Preparation of novel 1-[3-(1,8-naphthyridin-2-yl)phenyl]-3-phenylurea derivatives (6a-6q): To a stirred ...

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