Diisopropyl 2,2'-Bipyridine-3,3'-dicarboxylate

2,2'-Bipyridine-3,3'-dicarboxylic acid (2) was prepared from 1,10-phenanthroline 1 by a literature procedure [1,2]. 2,2'-Bipyridine-3,3'-dicarboxylic acid (2, 600 mg, 2,5 mmol) and thionyl chloride (6 ml) were refluxed for 5 hours. The excess amount of thionyl chloride was distilled off and the residue dried in vacuum for 5 hours. Toluene (20 ml) and isopropanol (1.4 ml, 18.2 mmol) were added and the mixture refluxed for 20 hours. Chloroform (40 ml) was added and the mixture was treated with a cold solution of sodium bicarbonate (2.5 %). The organic layer was dried on sodium sulphate and the solvent removed in vacuum, giving 890 mg of crude product. The product was purified by chromatography on silica gel column using ether as eluent to afford 3 as a white solid (600 mg, 73%).

M.p. 81-82 °C.

IR (KBr, cm-1): 1695, 1535, 1415, 1260.

1H-NMR (250 MHz, CDCl3): 8.73 (dd; 2H, H6/6', J = 4.8 and 1.7 Hz); 8.37 (dd, 2H, H4/4', J = 7.9 and 1.7 Hz); 7.46 (dd, 2H, H5/5', J = 7.9 and 4.8 Hz), 4.95 (m, 2H, 2CH), 0.97 (d, 12H, 4CH3).

Anal. Cal. for C18H20N2O4 (328.37): C 65.84, H 6.14, N 8.53; found : C 65.78, H 6.22, N 8.57.