Dabco → 7-(3-Fluoro-benzyl)-2-methyl-6-oxo-4-[4-(thiophene-2-carbonyl)-piperazin-1-yl]-6,7-dihydro-thieno[2,3-b]pyridine-5-carboxylic acid ethyl ester

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A solution of 4-chloro-7-(3-fluoro-benzyl)-2-methyl-6-oxo-6,7-dihydro-thieno[2,3-b]pyrdine-5-carboxylic acid ethyl ester (70) (3.0 g, 7.89 mmol), piperazin-1-yl-thiophen-2-yl-methanone (1.78 g, 9.09 mmol), and DABCO (1.02 g, 9.09 mmol) in anhydrous DMF was heated overnight at 110° C. The solution was cooled and poured into a 2% ammonium chloride aqueous solution. The precipitated solid was collected by vacuum filtration. The solid was redissolved in dichloromethane and filtered. The filtrate was concentrated under vacuum and the residue was purified by flash chromatography eluting with 0-5% MeOH in CH2Cl2 gradient to yield 2.8 g (65%) of 7-(3-fluoro-benzyl)-2-methyl-6-oxo-4-[4-(thiophene-2-carbonyl)-piperazin-1-yl]-6,7-dihydro-thieno[2,3-b]pyridine-5-carboxylic acid ethyl ester. 1H-NMR (DMSO-d6) δ 1.29 (t, J=7.2 Hz, 3H), 2.43 (s, 3H), 3.29 (m, 4H), 3.81 (m, 4H), 4.26 (q, J=7.2 Hz, 2H), 5.23 (s, 2H), 6.99 (d, J=1.2 Hz, 1H), 7.06-7.16 (m, 4H), 7.41 (m, 1H), 7.46 (dd, J=1.2, 4.0 Hz, 1H), 7.79 (dd, J=1.2, 4.8 Hz, 1H); EIMS m/z 540(M+1).

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